VT420 Flyback Transformer Needed
urbancamo
Well, my VT420 let out some magic smoke the other day, and is no
longer happy. Upon visual inspection I would say the flyback
transformer is no longer alive. I don't suppose anyone has one kicking
around in their collection of parts they could let me have (or
alternatively the board in which it sits)? Would be a shame to have to
skip the whole terminal.
Many thanks, Mark.
GreyCloud
Unfortunately, you'll need more than the flyback to fix it.
You'll need a schematic to identify the parts near it as well. The
capacitors and a diode usually go first and are the cause of the flyback
failure.
Neil Rieck
I just found two refurbished VT-420 terminals on eBay.com going for
$65. Alternatively, you might wish to purchase a new VT-520 or put an
emulator on a cheap PC.
Neil Rieck
Kitchener / Waterloo / Cambridge,
Ontario, Canada.
http://www3.sympatico.ca/n.rieck/OpenVMS.html
GreyCloud
Then he can try and get the eBay terminals. $65 is a good price.
There is a problem tho on refurbished boards... if the area where the
flyback is located is burned pretty good, then that section of the board
will be carbonized and present a resistive load that can change the
circuits characteristics. Our shop had a circuit board repair facility
that could grind out the carbonized sections and then fill in with the
appropriate materials. A new VT-520 would be the better way to go if he
can afford it.
nobody
Mark, Where are you located?
I have two VT-420 terminals that were working last time I checked (5y+
ago). Have been considering taking them to the recycling facility. But
yhey are located in Sweden.
urbancamo
> I have two VT-420 terminals that were working last time I checked (5y+
> ago). Have been considering taking them to the recycling facility. But
> yhey are located in Sweden.
Hi, I'm in the UK. I'd be happy to pay postage if it's not too
horrendous - my email is mark at wickensonline dot co dot uk if you
want to email me direct.
Cheers, Mark.
Scott Dorsey
What makes you think the flyback is really gone? Usually what goes on
these is the sweep transistor which takes out the emitter resistor
and sometimes some caps.
The flybacks have been known to fail before. There's a place in western
Virginia that has them.... I will see if I can come up with the name.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
urbancamo
http://www.wickensonline.co.uk/images/flyback-1.jpg
http://www.wickensonline.co.uk/images/flyback-2.jpg
Looks like the magic smoke eminated from the transformer itself.
jjh
the pictures look rather convincing, but, I'd perform a few tests if
you have the equipment:http://www.repairfaq.org/sam/flytest.htm#flywdf
Look at the section "Flyback failure and Testing"
These techniques are well known to techs (and engineers) that do
service work. I learned them from my father who had been in the
business for 50+ yrs. What is written here is a very good guide
(IMHO).
-John
Scott Dorsey
>
>http://www.wickensonline.co.uk/images/flyback-1.jpg
>
>http://www.wickensonline.co.uk/images/flyback-2.jpg
>
>Looks like the magic smoke eminated from the transformer itself.
I can't really tell... there is a place on the side where the conformal coat
is gone, and I am curious about that.
Anyway, the Sampo FDA075 is used in a lot of different monitors. You can
try www.acme-sales.net and also MCM Electronics. I think that is the same
as the FDA019B and FDA049, also.
PLEASE check the damping diode and the sweep transistor before putting a new
flyback in, though.
jjh
I forgot to mention that Sampo made a lot of flybacks as well as
televisions and monitors. I would be surprised if you could not find
the exact replacement or a cross from a television parts supplier.
jjh
One last thing...the writeup also lists suppliers of flybacks. NTE,
Dalbani, HR diemen are 'well known' to service techs in the states.
Not sure who is around in your neck of the woods....
jjh
so sorry for the noise, my mind is not quite in gear. As another
person pointed out, that what often dies is the HOT (horizontal output
transistor), and the capacitors and rectifiers that surround the
flyback. Generally, it is a good service practice to replace the HOT
as well as the caps. IMHO, the capacitors are the most critical - age
+ heat dries them out. If you replace the flyback you will most likely
increase the stress on the caps which when they fail, will most likely
take out the new flyback. It is generally a good idea to replace the
caps with the identical p/n of caps, or a newer equivalent that has a
low ESR (Equivalent Series Resistance) value. This is a fairly new
(within the last 10 yrs) metric applied to caps that are primarly used
in switched mode power supplies, of which a flyback circuit is a form.
Good luck
-J
Bill Gunshannon
Seems to me that by the time you get done acquiring all the parts,
troubleshooting the thing and making the repairs it would have been
a lot cheaper and easier to can it and get another. Replacements
are not that hard to come up with.
bill
--
Bill Gunshannon | de-moc-ra-cy (di mok' ra see) n. Three wolves
bill...@cs.scranton.edu | and a sheep voting on what's for dinner.
University of Scranton |
Scranton, Pennsylvania | #include <std.disclaimer.h>
GreyCloud
http://www.mectronic.com/scripts/NewDemo/partlist.asp?txtPartno1=FDA075&txtManufacturer1=SAMPO
Looks like you may be able to get one here.
If that is all that is wrong, but I doubt it.
GreyCloud
Quite correct. He needs to be able to identify the output transistor as
well as any of the associated diodes and caps. He'll also have to look
for other fried components. If he has a digital multimeter with diode
check built in, he should be able to test these.
The diode should read a very low resistance in one direction and open in
the other direction. The cap shouldn't read any resistance, but may
show on initial contact an increasing resistance, which may be a good
indicator but will not show if it can withstand the working voltage.
VAXman-
New digital multimeters have capacitance, inductance and more transistor
check settings too. However, in most cases, to check these properly, it
has to be removed from the circuit. Checking a capacitor in circuit may
show resistance as these are often used in RC (time) configurations:
|
---+---
| |
> |
< ===
> |
| |
---+---
|
Metering across the cap in this case will nearly always show as a leaky
cap. High voltage circuits may also have bleeder resistors which would
show, albeit typically much higher, resistance.
--
VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG
http://www.quirkfactory.com/popart/asskey/eqn2.png
Yeah. You know, it occurs to me that the best way you hurt rich people is by
turning them into poor people. -- Billy Ray Valentine
GreyCloud
The digital meters have a limited capacitance range and most won't go
over 100 ufd. Plus they don't test for the working voltage.
And yes, you have to unsolder the components. Usually, a visual
inspection helps as well. But for the sake of ease, he still would be
better off to shop around for another terminal.
Keith F. Lynch
> Seems to me that by the time you get done acquiring all the parts,
> troubleshooting the thing and making the repairs it would have been
> a lot cheaper and easier to can it and get another. Replacements
> are not that hard to come up with.
They're getting harder to come up with, as VT420s are no longer made.
I have three VT420s at home; I'm using one now. I have several
keyboards for them, but most of the keyboards have gradually become
less and less usable.
I remember about 25 years ago the place I where was working bought
a couple of used DEC RP04 disk drives for a low price, and got a
maintenance contract that cost about as much per month as the drives
cost. I suggested foregoing the maintenance and just replacing them
when they break, but was told that the supply of replacements was sure
to dry up.
I hope nobody discards any VT420s or keyboards, whether they're
working or not. Even if they're not working, they can be used as a
source of replacement parts for other VT420s.
It's good to see discussion of actual terminals on comp.terminals.
--
Keith F. Lynch - http://keithlynch.net/
Please see http://keithlynch.net/email.html before emailing me.
Neil Rieck
Boundless Technologies at one time had the rights to manufacture VT510
( and 520 and 525) terminals.
http://www.boundless.com/terminals.html
http://www.boundless.com/specsheets/VT510_520%20Spec.pdf
People still buy new character cells terminals because no one will
steal them. In almost every computer room in the world someone will
borrow your console device (VGA monitor or PC w/emulator) never to be
seen again.
NSR
VAXman-
>over 100 ufd. Plus they don't test for the working voltage.
>And yes, you have to unsolder the components. Usually, a visual
>inspection helps as well. But for the sake of ease, he still would be
>better off to shop around for another terminal.
I high quality Wavetek meter here.
Anyway, I was an undergrad and graduate EE student. In college, I and
some friends would pickup old TVs tossed at the curb and fix them up in
the EE and physics labs where I worked. We'd always keep the best TV
and others were sold for sustenance (read, beer money).
It's not practical today to repair most. I have a small (30"?) LCD TV
that has been acting up. Something in the power supply I believe. I
have opened it and there are 2 main boards (PS and TV logic). All is
surface mount. I contacted the mfg for replacement part prices. The
PS is nearly 1/2 the price of the original TV purchase. Hence, we have
created an industry of landfill fodder.
I too think that it might be wise to just purchase a new VT4xx. Unless
this repair is academic, it may become costly to repair if all damaged
components aren't diagnosed and replaced. ;)
jjh
IMHO, one is better off just to replace the caps, right off the bat.
In my many years of experience trying to test them, using various
meters and methods, the problem is breakdown under load, which is very
difficult to determine statically, or simulated dynamic conditions
outside of the actual circuit. The two main reasons are: heat, and
operating voltage and frequencies. Meters will show false positives,
and generally are fairly good at "showing the obvious e.g.
short"...Dynamic tests at certain frequencies will show capacitance
value at that frequency and voltage, but the voltage is not the
working voltage, which is where the problem lies. Various ESR meters
will provide a rough order of magnitude of 'quality' but the scale
derived by heuristics based on capacitor chemistry.
As far as 'cheaper to just replace the terminal'...well [soapbox
on]....I beg to differ. At what point does the value of time become
less important that functionality or preservation of resources
(e.g.landfills)? Repairing a flyback is a reasonable repair. It
*may* cost more than someones *perceived value* of the device, but
that is relative. If the device is used in a production setting where
MTTR is required to be less than 5 mins, then stand by sparing is the
way to go, and fix the dead device during non critical times. If the
device is in a hobby environment, then MMTR is not critical and can be
dealt with by a windoz terminal emulator till repair is effected.
From my POV, the 'cost of repair' hardly ever outweighs the secondary
costs of landfill fodder. [soapbox off]. Of course the marketing
ppl will have you believe that if it doesn't look new, snazzy, have a
gazillion modes that one will never use, or doesn't look 'right' given
the environment (a very meaningful metric brought to you by the
'fashion conscience') then you need to upgrade and trash what you
have. Something very wrong about this scenario...lol
-J
GreyCloud
:-) Those were the days.
>
> It's not practical today to repair most. I have a small (30"?) LCD TV
> that has been acting up. Something in the power supply I believe. I
> have opened it and there are 2 main boards (PS and TV logic). All is
> surface mount. I contacted the mfg for replacement part prices. The
> PS is nearly 1/2 the price of the original TV purchase. Hence, we have
> created an industry of landfill fodder.
>
I just read this mornings comic strip, Dagwood, where the kid told his
sister that TVs used to be repaired and not thrown away. She didn't
believe him. Trying to repair surface mount can be done with the right
tools (very expensive ones), but then getting the parts is even harder.
> I too think that it might be wise to just purchase a new VT4xx. Unless
> this repair is academic, it may become costly to repair if all damaged
> components aren't diagnosed and replaced. ;)
>
Wyse is still making terminals, but I don't now how compatible they'd be
with VMS.
glen herrmannsfeldt
(snip)
>> It's not practical today to repair most. I have a small (30"?) LCD TV
>> that has been acting up. Something in the power supply I believe. I
>> have opened it and there are 2 main boards (PS and TV logic). All is
>> surface mount. I contacted the mfg for replacement part prices. The
>> PS is nearly 1/2 the price of the original TV purchase. Hence, we have
>> created an industry of landfill fodder.
> I just read this mornings comic strip, Dagwood, where the kid told his
> sister that TVs used to be repaired and not thrown away. She didn't
> believe him. Trying to repair surface mount can be done with the right
> tools (very expensive ones), but then getting the parts is even harder.
(snip)
There is currently a commercial for the Washington state prepaid
tuition plan featuring parents discovering their kid working
on a computer motherboard with a large screwdriver. The voice over
then says that they don't have to worry about college expenses...
But everyone knows you can't work on such boards, especially not with
a big screwdriver.
-- glen
urbancamo
would be a HV discharge tool. Am I right in thinking that a 5 watt 5
MOhm resister with suitable screening would do the trick?
VAXman-
>
>>
>> that has been acting up. Something in the power supply I believe. I
>> have opened it and there are 2 main boards (PS and TV logic). All is
>> surface mount. I contacted the mfg for replacement part prices. The
>> PS is nearly 1/2 the price of the original TV purchase. Hence, we have
>> created an industry of landfill fodder.
>>
>
>sister that TVs used to be repaired and not thrown away. She didn't
>believe him. Trying to repair surface mount can be done with the right
>tools (very expensive ones), but then getting the parts is even harder.
I'll have to look for that one. However, looking through the offerings
at places like BestBuys and Costco, etc., a flat panel TV can be had at
a few $100 these days. The average TV repair shop will ask you to drop
a C-note just to leave a repair item with their shop. I think TV repair-
men are becoming the new breed of "the lonely Maytag repairmen".
>> I too think that it might be wise to just purchase a new VT4xx. Unless
>> this repair is academic, it may become costly to repair if all damaged
>> components aren't diagnosed and replaced. ;)
>>
>
>Wyse is still making terminals, but I don't now how compatible they'd be
>with VMS.
I remember some of those. Their VT emulation was OK. I even had one
here but I gave it away (might have been with a haul that Bob Koehler
took away). The one I had was the "alien" green screen which I didn't
find easy on the eyes so I seldom used it. I prefer my chalkboard and
yellowjacket, still functioning, VT100, VT220, VT320, VT420, VT510 and
VT525 (full color) terminals; albeit, I spend most of my time working
via xterms under Linux laptop SSHed into VMS.
VAXman-
Yes, that might do you. Do be careful! I've had discharges through me
back in those TV repair days. Obvioulsy, none lethal but they sure as
hell did smart! I remember one case. The then not yet Mrs. VAXman was
waiting in the lab for me when she said "what is that I smell burning?"
I replied, "Me!" I took a discharge that burned a hole through my thumb
from the middle of the top of the nail straight through. Smarted like
all hell for days! Fortunately, it was a long recess weekend on campus
with plenty of free pain numbing libations to easy the pain of the burn.
When I wasn't drinking, my thumb stayed in the beer in the beer mug.
FWIW, a quick googling shows several sites with VT420 for sale:
http://www.mticom.com/dec/dec.asp?ppc=gle
http://dec.vecmar.com/products/productpage.asp?pid=608&source=google&gclid=CPPD-LzOsKACFWV75Qodwz2LUw
Check these for pricing and then weigh that with the cost of your repair
items and your probablility of successfully restoring yours to its former
glory.
Scott Dorsey
>
>Wyse is still making terminals, but I don't now how compatible they'd be
>with VMS.
Pretty well. They even implement the VT-100 "last character" bug correctly.
RSX and VMS users have it pretty easy since the systems were designed to work
with terminals that were very close to the ANSI standard. Much better off
than, say, the HP/3000 fans who are stuck with weird proprietary terminal
sequences.
Scott Dorsey
I've always just used a wire with no bleeder resistor. 1/2W 5M should
be fine although you might have to wait a good while for the charge to go
down that way.
JF Mezei
> Yes, that might do you. Do be careful! I've had discharges through me
> back in those TV repair days.
Is this what caused you to be left handed ? :-) :-) :-) :-)
Bill Gunshannon
I, too, have been hit by that. Actually, it was not as bad as getting
hit with 700v (from a 700v center tapped transformer feeding a 5U4 to
deliver 350v DC to an old RCA radio.) That one threw me out of my roll-
around chair and clean across the room. Learned an important lesson
that day. And understood well why Navy radiomen and Electronic Techs
were taught to keep one hand in their pocket when I was taught that. :-)
Richard B. Gilbert
> VAXman- @SendSpamHere.ORG wrote:
>> In article <TMKdnQYAVMvLcAvW...@bresnan.com>, GreyCloud
>> <mi...@cumulus.com> writes:
>>> VAXman- @SendSpamHere.ORG wrote:
>>>> In article <lu-dndCjKpjmFwjW...@bresnan.com>, GreyCloud
>>>> <mi...@cumulus.com> writes:
>>>>> jjh wrote:
>>>>>> On Mar 8, 3:17 am, urbancamo <m...@wickensonline.co.uk> wrote:
>>>>>>> On Mar 8, 1:16 am, klu...@panix.com (Scott Dorsey) wrote:
>>>>>>>
>
> Wyse is still making terminals, but I don't now how compatible they'd be
> with VMS.
VT-100 is a superset of an ANSI Standard, X3-64 if memory serves me.
VT-2xx is a superset of VT-100
A lot of terminals emulate and software such as Reflection from Walker,
Richer, and Quinn will turn your PC into a reasonable approximation of a
VT-240 or VT-340. The PC keyboard is not equivalent to the DEC keyboard
and you may need to use "point and click" emulation for the DEC keypad.
Richard B. Gilbert
If there's a big capacitor in the circuit you may die of old age before
it finishes discharging!
I'd try a much smaller value.
VAXman-
>VAXman- @SendSpamHere.ORG wrote:
>
>> back in those TV repair days.
>
No, it was through the thumb of the left hand.
Michael Moroney
>I, too, have been hit by that. Actually, it was not as bad as getting
>hit with 700v (from a 700v center tapped transformer feeding a 5U4 to
>deliver 350v DC to an old RCA radio.) That one threw me out of my roll-
>around chair and clean across the room. Learned an important lesson
>that day. And understood well why Navy radiomen and Electronic Techs
>were taught to keep one hand in their pocket when I was taught that. :-)
I did that as well. Playing with the power transformer from an old
tube-type TV which was also 700VCT. I still don't know for sure if I got
zapped with 350V or 700V, as it would depend on whether I handled the CT
or both non-CT leads.
Jan-Erik Soderholm
> GreyCloud wrote:
>> VAXman- @SendSpamHere.ORG wrote:
>>> In article <TMKdnQYAVMvLcAvW...@bresnan.com>, GreyCloud
>>> <mi...@cumulus.com> writes:
>>>> VAXman- @SendSpamHere.ORG wrote:
>>>>> In article <lu-dndCjKpjmFwjW...@bresnan.com>,
>>>>> GreyCloud <mi...@cumulus.com> writes:
>>>>>> jjh wrote:
>>>>>>> On Mar 8, 3:17 am, urbancamo <m...@wickensonline.co.uk> wrote:
>>>>>>>> On Mar 8, 1:16 am, klu...@panix.com (Scott Dorsey) wrote:
>>>>>>>>
> <huge snip>
>>
>> Wyse is still making terminals, but I don't now how compatible they'd
>> be with VMS.
>
> VT-100 is a superset of an ANSI Standard, X3-64 if memory serves me.
> VT-2xx is a superset of VT-100
>
> A lot of terminals emulate and software such as Reflection from Walker,
WRQ was bought many years ago by Attachmate vut still developes
and sells Reflection. One of the best emulators, I'd say.
Latest I've heard from Attachmate is that the next version will
be a replacement for both Reflection and Extra! (which is/was
Attachmates own product before they baught WRQ).
will turn your PC into a reasonable approximation of a
> VT-240 or VT-340. The PC keyboard is not equivalent to the DEC keyboard
> and you may need to use "point and click" emulation for the DEC keypad.
As long as you at least have a full PC kayboard you should be fine.
Laptops (without the separate num kaypad) is another story.
John Reagan
"Jan-Erik Soderholm" <jan-erik....@telia.com> wrote in message
news:hnbm09$gf6$1...@news.albasani.net...
>
> WRQ was bought many years ago by Attachmate vut still developes
> and sells Reflection. One of the best emulators, I'd say.
>
> Latest I've heard from Attachmate is that the next version will
> be a replacement for both Reflection and Extra! (which is/was
> Attachmates own product before they baught WRQ).
>
>
I use PuTTY on my PC to OpenVMS. Keypad works great with LSE, Notes, etc.
I have an LSE keybinding to map F9,F10,F11,F12 to the DO key so I just hit
any of those keys. Plus it is free.
John
GreyCloud
Don't need it. Use a long screwdrive, some copper braid or wire with
some good alligator clips on each end, then clip the wire to the
screwdriver and the other end to board ground. Then slip the
screwdriver blade underneath the high voltage cup on the crt. You'll
hear a nice snap... and leave it there for a few seconds. Then you are
done and don't have to worry about getting nailed. If you leave the crt
disconnected for a week, do not touch the crt anode where the cup
attaches, as for some reason it will acquire a charge again. Got nailed
on that one a long time ago.
jjh
Ditto...skip the R. Been doing this a looooong time, never any bad
side effects.
-John
Bob Koehler
> sister that TVs used to be repaired and not thrown away. She didn't
> believe him. Trying to repair surface mount can be done with the right
> tools (very expensive ones), but then getting the parts is even harder.
Yep. Kids today don't know what it's like to have a tube blow in the
middle of thier TV show, and wait for the TV repairman to show up.
Bob Koehler
>
> I remember some of those. Their VT emulation was OK. I even had one
> here but I gave it away (might have been with a haul that Bob Koehler
> took away).
Nope. They only tube I took was the one attached to the Pro.
But I got a good price on a VT420 at the used item sale at UMD.
Got most of my storage their, too.
Bob Koehler
>
> RSX and VMS users have it pretty easy since the systems were designed to work
> with terminals that were very close to the ANSI standard. Much better off
> than, say, the HP/3000 fans who are stuck with weird proprietary terminal
> sequences.
Or ADM, which used bell instead of escape. Just try sending a reply
message to one of those!
Keith F. Lynch
> If you leave the crt disconnected for a week, do not touch the crt
> anode where the cup attaches, as for some reason it will acquire a
> charge again. Got nailed on that one a long time ago.
That happens because the charge is in the glass. Just because it's
a poor conductor doesn't mean it won't hold a charge. It does mean
that the charge won't drain through your screwdriver and ground strap
unless you leave them connected for weeks.
A cool physics demonstration is to charge a leyden jar, completely
dismantle it, short together and ground all the metal pieces, then
reassmble it. The charge will be back! Of course it never left.
It was in the glass of the jar all along.
Keith F. Lynch
> VT-100 is a superset of an ANSI Standard, X3-64 if memory serves me.
> VT-2xx is a superset of VT-100
> A lot of terminals emulate and software such as Reflection from
> Walker, Richer, and Quinn will turn your PC into a reasonable
> approximation of a VT-240 or VT-340.
But do they, or any other terminal or terminal emulator, support
TD/SMP, the protocol that allows multiple sessions on one wire?
And do shells on Linux, the BSDs, or OS/X support it? Thanks.
Richard B. Gilbert
> Richard B. Gilbert <rgilb...@comcast.net> wrote:
>> VT-100 is a superset of an ANSI Standard, X3-64 if memory serves me.
>> VT-2xx is a superset of VT-100
>
>> A lot of terminals emulate and software such as Reflection from
>> Walker, Richer, and Quinn will turn your PC into a reasonable
>> approximation of a VT-240 or VT-340.
>
> But do they, or any other terminal or terminal emulator, support
> TD/SMP, the protocol that allows multiple sessions on one wire?
> And do shells on Linux, the BSDs, or OS/X support it? Thanks.
Not that I know of. I never heard of TD/SMP.
Bob Eager
> Richard B. Gilbert <rgilb...@comcast.net> wrote:
>> VT-100 is a superset of an ANSI Standard, X3-64 if memory serves me.
>> VT-2xx is a superset of VT-100
>
>> A lot of terminals emulate and software such as Reflection from Walker,
>> Richer, and Quinn will turn your PC into a reasonable approximation of
>> a VT-240 or VT-340.
>
> But do they, or any other terminal or terminal emulator, support TD/SMP,
> the protocol that allows multiple sessions on one wire?
Surely it's proprietary? It would have to be licensed.
> And do shells on
> Linux, the BSDs, or OS/X support it? Thanks.
Shells don't support these things. You wouldn't ask if DCL supported
it...!
--
Use the BIG mirror service in the UK:
http://www.mirrorservice.org
Jan-Erik Soderholm
> Richard B. Gilbert<rgilb...@comcast.net> wrote:
>> VT-100 is a superset of an ANSI Standard, X3-64 if memory serves me.
>> VT-2xx is a superset of VT-100
>
>> A lot of terminals emulate and software such as Reflection from
>> Walker, Richer, and Quinn will turn your PC into a reasonable
>> approximation of a VT-240 or VT-340.
>
> But do they, or any other terminal or terminal emulator, support
> TD/SMP, the protocol that allows multiple sessions on one wire?
> And do shells on Linux, the BSDs, or OS/X support it? Thanks.
What does "wire" realy mean here ?
I can run *a lot* of "multiple session on on e wire" using
Reflection from my PC.
Asking about TD/SMP when talking about software terminal emulators
seems to me to be asking the wrong questions.
GreyCloud
> GreyCloud <mi...@cumulus.com> wrote:
>> If you leave the crt disconnected for a week, do not touch the crt
>> anode where the cup attaches, as for some reason it will acquire a
>> charge again. Got nailed on that one a long time ago.
>
> That happens because the charge is in the glass. Just because it's
> a poor conductor doesn't mean it won't hold a charge. It does mean
> that the charge won't drain through your screwdriver and ground strap
> unless you leave them connected for weeks.
>
> A cool physics demonstration is to charge a leyden jar, completely
> dismantle it, short together and ground all the metal pieces, then
> reassmble it. The charge will be back! Of course it never left.
> It was in the glass of the jar all along.
That is interesting. I discharged a lot of Crts in my time and stored
them on the shelf. Initially I touch the anode after a good discharge
and found no charge there. A couple of months later I got nailed.
Bill Pechter
Another really nice option is Kermit-95 from Columbia.
Does all the vtxxx stuff you could ask for.
http://www.columbia.edu/kermit/k95faq.html
Bill
--
"When I think back on all the crap I learned in Vax school
It's a wonder I fixed anything at all." (to the tune of Kodachrome)
pechter-at-ureach.com
H Vlems
> "Jan-Erik Soderholm" <jan-erik.soderh...@telia.com> wrote in message
PuTTY is a very good piece of software indeed. I paid for my WRQ
Reflection kit, which I like for it support of Burroughs T27 and Data
General terminals but I could live with just PuTTY alone. It gets
installed on all pc's at home right after installing Grisoft's AVG
software.
Hans
H Vlems
Which makes a Leiden jar (Leidse fles) a very nice tool to demonstrate
what electrical current actually is: charge per second.
Hans
VAXman-
>On Mar 13, 9:48=A0pm, "Keith F. Lynch" <k...@KeithLynch.net> wrote:
>> GreyCloud <m...@cumulus.com> wrote:
>> > If you leave the crt disconnected for a week, do not touch the crt
>> > anode where the cup attaches, as for some reason it will acquire a
>>
>> That happens because the charge is in the glass. =A0Just because it's
>> a poor conductor doesn't mean it won't hold a charge. =A0It does mean
>> that the charge won't drain through your screwdriver and ground strap
>> unless you leave them connected for weeks.
>>
>> A cool physics demonstration is to charge a leyden jar, completely
>> dismantle it, short together and ground all the metal pieces, then
>> It was in the glass of the jar all along.
>> --
>> Keith F. Lynch -http://keithlynch.net/
>> Please seehttp://keithlynch.net/email.htmlbefore emailing me.
>
>Which makes a Leiden jar (Leidse fles) a very nice tool to demonstrate
>what electrical current actually is: charge per second.
>Hans
No, an electrical current is actually a movement of charge. It's unit
of measurement is the amount of charge that has move per unit of time.
Bill Gunshannon
I would have to dig around but I thought there was a program
distributed in comp.sources.unix (shock, shock, Stallman really
didn't invent Open Source!!) long a go that allowed for multiple
shells running in "windows" on character cell terminals. And,
I expect if I am right it worked on any terminal supported by
termcap.
Bill Gunshannon
Bill Pechter <pec...@tucker.pechter.dyndns.org> writes:
> On 2010-03-11, Richard B. Gilbert <rgilb...@comcast.net> wrote:
>> GreyCloud wrote:
>>> VAXman- @SendSpamHere.ORG wrote:
>>>> In article <TMKdnQYAVMvLcAvW...@bresnan.com>, GreyCloud
>>>> <mi...@cumulus.com> writes:
>>>>> VAXman- @SendSpamHere.ORG wrote:
>>>>>> In article <lu-dndCjKpjmFwjW...@bresnan.com>, GreyCloud
>>>>>> <mi...@cumulus.com> writes:
>>>>>>> jjh wrote:
>>>>>>>> On Mar 8, 3:17 am, urbancamo <m...@wickensonline.co.uk> wrote:
>>>>>>>>> On Mar 8, 1:16 am, klu...@panix.com (Scott Dorsey) wrote:
>>>>>>>>>
>><huge snip>
>>>
>>> Wyse is still making terminals, but I don't now how compatible they'd be
>>> with VMS.
>>
>> VT-100 is a superset of an ANSI Standard, X3-64 if memory serves me.
>> VT-2xx is a superset of VT-100
>>
>> A lot of terminals emulate and software such as Reflection from Walker,
>> Richer, and Quinn will turn your PC into a reasonable approximation of a
>> VT-240 or VT-340. The PC keyboard is not equivalent to the DEC keyboard
>> and you may need to use "point and click" emulation for the DEC keypad.
>>
>>
>
> Another really nice option is Kermit-95 from Columbia.
> Does all the vtxxx stuff you could ask for.
> http://www.columbia.edu/kermit/k95faq.html
So does plain ordinary MSDOS Kermit and it has the advantage of
being free. Put it on any old PC (all the way back to an 8088)
and you have a great terminal. I have used this for PDP-11 and
VAX consoles for years and years. And that even though I have
a stack of VT240's here at the house.
H Vlems
> In article <11547d94-bf6c-49b4-854a-1d8e4de32...@g28g2000yqh.googlegroups.com>, H Vlems <hvl...@freenet.de> writes:
>
>
>
>
>
> >On Mar 13, 9:48=A0pm, "Keith F. Lynch" <k...@KeithLynch.net> wrote:
> >> GreyCloud <m...@cumulus.com> wrote:
> >> > If you leave the crt disconnected for a week, do not touch the crt
> >> > anode where the cup attaches, as for some reason it will acquire a
> >> > charge again. =A0Got nailed on that one a long time ago.
>
> >> That happens because the charge is in the glass. =A0Just because it's
> >> a poor conductor doesn't mean it won't hold a charge. =A0It does mean
> >> that the charge won't drain through your screwdriver and ground strap
> >> unless you leave them connected for weeks.
>
> >> A cool physics demonstration is to charge a leyden jar, completely
> >> dismantle it, short together and ground all the metal pieces, then
> >> reassmble it. =A0The charge will be back! =A0Of course it never left.
> >> It was in the glass of the jar all along.
> >> --
> >> Keith F. Lynch -http://keithlynch.net/
>
> >Which makes a Leiden jar (Leidse fles) a very nice tool to demonstrate
> >what electrical current actually is: charge per second.
> >Hans
>
> No, an electrical current is actually a movement of charge. It's unit
> of measurement is the amount of charge that has move per unit of time.
>
> --
> VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)ORG
>
> http://www.quirkfactory.com/popart/asskey/eqn2.png
>
> Yeah. You know, it occurs to me that the best way you hurt rich people is by
>
> - Show quoted text -
1 Ampere is 1 Coulomb per second.
Scott Dorsey
>I would have to dig around but I thought there was a program
>distributed in comp.sources.unix (shock, shock, Stallman really
>didn't invent Open Source!!) long a go that allowed for multiple
>shells running in "windows" on character cell terminals. And,
>I expect if I am right it worked on any terminal supported by
>termcap.
You're talking about layers. It's a good thing. Early versions also
supported multiple windows on the AT&T 5620 dmd, but that's a different
newsgroup.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
VAXman-
>On Mar 14, 2:46=A0pm, VAXman- @SendSpamHere.ORG wrote:
>> In article <11547d94-bf6c-49b4-854a-1d8e4de32...@g28g2000yqh.googlegroups=
>..com>, H Vlems <hvl...@freenet.de> writes:
>>
>>
>>
>>
>>
>> >On Mar 13, 9:48=3DA0pm, "Keith F. Lynch" <k...@KeithLynch.net> wrote:
>> >> GreyCloud <m...@cumulus.com> wrote:
>> >> > If you leave the crt disconnected for a week, do not touch the crt
>> >> > anode where the cup attaches, as for some reason it will acquire a
>>
>> >> That happens because the charge is in the glass. =3DA0Just because it'=
>s
>> >> a poor conductor doesn't mean it won't hold a charge. =3DA0It does mea=
>n
>> >> that the charge won't drain through your screwdriver and ground strap
>> >> unless you leave them connected for weeks.
>>
>> >> A cool physics demonstration is to charge a leyden jar, completely
>> >> dismantle it, short together and ground all the metal pieces, then
>ft.
>> >> It was in the glass of the jar all along.
>> >> --
>> >> Keith F. Lynch -http://keithlynch.net/
>>
>> >Which makes a Leiden jar (Leidse fles) a very nice tool to demonstrate
>> >what electrical current actually is: charge per second.
>> >Hans
>>
>> of measurement is the amount of charge that has move per unit of time.
>>
>> --
>dot)ORG
>>
>> =A0http://www.quirkfactory.com/popart/asskey/eqn2.png
>>
>> Yeah. You know, it occurs to me that the best way you hurt rich people is=
> by
>> turning them into poor people. -- Billy Ray Valentine- Hide quoted text -
>>
>> - Show quoted text -
>
>1 Ampere is 1 Coulomb per second.
Correct, a definition of a unit of measurement but it is not a definition
of current.
Current (I) is a change of or movement of charge (Q) per unit time (t).
Since you cannot create or destroy charges (laws of conservation), the
change in charge would result from a movement of it.
Ergo, I = dQ/dt
I'd take it further but it's difficult to express partial differentials,
integrals, vectors and subscripts (re Maxwell's Laws) using a text only
newsreader. I = dQ/dt will suffice.
Keith F. Lynch
> Keith F. Lynch wrote:
>> But do they, or any other terminal or terminal emulator, support
>> TD/SMP, the protocol that allows multiple sessions on one wire?
>> And do shells on Linux, the BSDs, or OS/X support it? Thanks.
> What does "wire" realy mean here ?
> I can run *a lot* of "multiple session on on e wire" using
> Reflection from my PC.
Sorry, I meant a single RS-232 serial port.
Keith F. Lynch
> Shells don't support these things. You wouldn't ask if DCL supported
> it...!
Sorry, I was clumsily trying to convey that I meant a shell host
supporting multiple simultaneous sessions from a single terminal over
a single RS-232 serial line using the TD/SMP protocol. As contrasted
with a Linux (or whatever) machine running a terminal emulator.
Of course I know that VMS supports the TD/SMP protocol. I don't know
if any other operating system does.
JF Mezei
> Current (I) is a change of or movement of charge (Q) per unit time (t).
> Since you cannot create or destroy charges (laws of conservation), the
> change in charge would result from a movement of it.
Excuse my ignorance here, but if you have electrons with 110V charge
flowing through a light bulb, won't their charge be severely diminished
after they passed through that light bulb ? (aka: discharged their
energy into heat/light).
H Vlems
The simple equation is sufficient. We're talking about the same thing
clearly.
And the finesse of what you're trying to tell me gets lost in the
misty clouds of the language difference.
I'll switch to dV/dt if you don't mind, (where V stands for volume of
a liquid :-)
Hans
Bob Eager
> Bob Eager <rd...@spamcop.net> wrote:
>> Shells don't support these things. You wouldn't ask if DCL supported
>> it...!
>
> Sorry, I was clumsily trying to convey that I meant a shell host
> supporting multiple simultaneous sessions from a single terminal over a
> single RS-232 serial line using the TD/SMP protocol. As contrasted with
> a Linux (or whatever) machine running a terminal emulator.
>
> Of course I know that VMS supports the TD/SMP protocol. I don't know if
> any other operating system does.
As I said, given that it's a proprietary protocol (for legacy
connections), I doubt any other system would bother these days.
Really useful in its time, mind!
Marc Van Dyck
You're mixing up everything. Charge is not measured in Volts, but in
Coulombs. Volts are used to measure a difference of potential. Yes,
this difference drops after going through any resistance, following
Ohm's law. But charge remains constant.
If you compare electricity with water flowing through tubes, charge
is equivalent to a volume of water (cubic meters), a current is a
dï¿œbit (cubic meters per second) and difference of potential is just
a difference of height, in meters. I leave to the reader the exercise
to convert Farads (unit of capacity) into that analogy.
--
Marc Van Dyck
VAXman-
>On Mar 14, 7:37=A0pm, VAXman- @SendSpamHere.ORG wrote:
>> In article <19482699-ebff-4b75-bf2b-2db2e130f...@g11g2000yqe.googlegroups=>> >On Mar 14, 2:46=3DA0pm, VAXman- =A...@SendSpamHere.ORG wrote:
>> >> In article <11547d94-bf6c-49b4-854a-1d8e4de32...@g28g2000yqh.googlegro=
>ups=3D>> >> >On Mar 13, 9:48=3D3DA0pm, "Keith F. Lynch" <k...@KeithLynch.net> wrot=
>e:
>> >> >> GreyCloud <m...@cumulus.com> wrote:
>> >> >> > If you leave the crt disconnected for a week, do not touch the cr=
>t
>> >> >> > anode where the cup attaches, as for some reason it will acquire =
>a
>> >> >> > charge again. =3D3DA0Got nailed on that one a long time ago.
>>
>> >> >> That happens because the charge is in the glass. =3D3DA0Just becaus=
>e it'=3D
>> >s
>> >> >> a poor conductor doesn't mean it won't hold a charge. =3D3DA0It doe=
>s mea=3D
>> >n
>> >> >> that the charge won't drain through your screwdriver and ground str=
>ap
>> >> >> unless you leave them connected for weeks.
>>
>> >> >> A cool physics demonstration is to charge a leyden jar, completely
>> >> >> dismantle it, short together and ground all the metal pieces, then
>ever le=3D
>> >ft.
>> >> >> It was in the glass of the jar all along.
>> >> >> --
>> >> >> Keith F. Lynch -http://keithlynch.net/
>> >> >> Please seehttp://keithlynch.net/email.htmlbeforeemailingme.
>>
>e
>> >> >what electrical current actually is: charge per second.
>> >> >Hans
>>
>unit
>> >> of measurement is the amount of charge that has move per unit of time.
>>
>> >> --
>TMESIS(=3D
>> >dot)ORG
>>
>> >> =3DA0http://www.quirkfactory.com/popart/asskey/eqn2.png
>>
>> >> Yeah. You know, it occurs to me that the best way you hurt rich people=
> is=3D
>> > by
>> >> turning them into poor people. -- Billy Ray Valentine- Hide quoted tex=
>t -
>>
>> >> - Show quoted text -
>>
>> >1 Ampere is 1 Coulomb per second.
>>
>> Correct, a definition of a unit of measurement but it is not a definition
>>
>> Current (I) is a change of or movement of charge (Q) per unit time (t).
>> Since you cannot create or destroy charges (laws of conservation), the
>> change in charge would result from a movement of it.
>>
>>
>> I'd take it further but it's difficult to express partial differentials,
>> integrals, vectors and subscripts (re Maxwell's Laws) using a text only
>>
>> --
>> VAXman- A Bored Certified VMS Kernel Mode Hacker =A0 =A0VAXman(at)TMESIS(=
>dot)ORG
>>
>> =A0http://www.quirkfactory.com/popart/asskey/eqn2.png
>>
>> Yeah. You know, it occurs to me that the best way you hurt rich people is=
> by
>> turning them into poor people. -- Billy Ray Valentine- Hide quoted text -
>>
>> - Show quoted text -
>
>clearly.
>And the finesse of what you're trying to tell me gets lost in the
>misty clouds of the language difference.
>I'll switch to dV/dt if you don't mind, (where V stands for volume of
>a liquid :-)
Cool. Now you want to get into fluid dynamics? How's your understanding
of tensor calculus? :)
Johnny Billquist
> Bob Eager <rd...@spamcop.net> wrote:
>> Shells don't support these things. You wouldn't ask if DCL supported
>> it...!
>
> Sorry, I was clumsily trying to convey that I meant a shell host
> supporting multiple simultaneous sessions from a single terminal over
> a single RS-232 serial line using the TD/SMP protocol. As contrasted
> with a Linux (or whatever) machine running a terminal emulator.
>
> Of course I know that VMS supports the TD/SMP protocol. I don't know
> if any other operating system does.
Unless my memory totally fails me, Ultrix support/supported it.
Don't know about OSF/1 though.
And of course, several DEC terminal servers, meaning in turn anything
talking LAT.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: b...@softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
Bob Koehler
>
> Excuse my ignorance here, but if you have electrons with 110V charge
> flowing through a light bulb, won't their charge be severely diminished
> after they passed through that light bulb ? (aka: discharged their
> energy into heat/light).
110V is a potential, not a charge. No electron ever gave up it's
charge. If you can find one that does, please apply for the Nobel
Prize in Physics.
Scott Dorsey
>> Shells don't support these things. You wouldn't ask if DCL supported
>> it...!
>
>Sorry, I was clumsily trying to convey that I meant a shell host
>supporting multiple simultaneous sessions from a single terminal over
>a single RS-232 serial line using the TD/SMP protocol. As contrasted
>with a Linux (or whatever) machine running a terminal emulator.
Wyse 520 will support TD/SMP. I think that's the only hardware terminal
that is currently manufactured which will support it. Lynwood used to
make a terminal emulator for the IBM PC that supported it, and I think
PCTerm supported it.
>Of course I know that VMS supports the TD/SMP protocol. I don't know
>if any other operating system does.
I think source code for Unix used to be available through DECUS, and I
know somebody had it running on Ultrix-32.
Just about everybody in the seventies had some kind of multidrop terminal
protocol. The Reflection software mentioned earlier in this thread originally
started out just emulating the HP 2626A terminal, which had a multidrop mode
that the HP/3000 MPE operating system supported, but which was incompatible
with the rest of the world. IBM, Sperry, and Burroughs also all had multidrop
protocols and terminals that could be set up to handle multiple sessions over
a multidrop line, all proprietary and incompatible with one another.
These days everything runs ip and we don't have to worry about that stuff
any more. But you can run layers if you want.
Johnny Billquist
> Keith F. Lynch <k...@KeithLynch.net> wrote:
>> Bob Eager <rd...@spamcop.net> wrote:
>>> Shells don't support these things. You wouldn't ask if DCL supported
>>> it...!
>> Sorry, I was clumsily trying to convey that I meant a shell host
>> supporting multiple simultaneous sessions from a single terminal over
>> a single RS-232 serial line using the TD/SMP protocol. As contrasted
>> with a Linux (or whatever) machine running a terminal emulator.
>
> Wyse 520 will support TD/SMP. I think that's the only hardware terminal
> that is currently manufactured which will support it. Lynwood used to
> make a terminal emulator for the IBM PC that supported it, and I think
> PCTerm supported it.
Well, doh! Except of course for the VT520 and VT525, which are still
manufactured.
http://www.boundless.com/terminals.html
DEC sold their terminal business, they didn't terminate it.
>> Of course I know that VMS supports the TD/SMP protocol. I don't know
>> if any other operating system does.
>
> I think source code for Unix used to be available through DECUS, and I
> know somebody had it running on Ultrix-32.
I think the Ultrix-32 support was official, and from DEC. I have never
seen a DECUS utility for this, but now that you have mentioned it, I'm
going to look around.
> Just about everybody in the seventies had some kind of multidrop terminal
> protocol. The Reflection software mentioned earlier in this thread originally
> started out just emulating the HP 2626A terminal, which had a multidrop mode
> that the HP/3000 MPE operating system supported, but which was incompatible
> with the rest of the world. IBM, Sperry, and Burroughs also all had multidrop
> protocols and terminals that could be set up to handle multiple sessions over
> a multidrop line, all proprietary and incompatible with one another.
Hmm. Your use of multidrop either differs from mine, or else this would
be something else.
The DEC protocol was/is for just one point-to-point line, where you
multiplex several sessions over it.
A multidrop, in my parlance, is a connection where you have
one-to-many/many-to-one. Usually together with some software protocol,
to manage things so that noone gets confused.
It usually takes a little wiring to get it sorted out as well, since you
cannot have several transmitters active and wired together, to one
receiver. DEC did this for DECnet, for instance. Can't remember the
interface now, but it was/is some kind of asynch serial interface.
> These days everything runs ip and we don't have to worry about that stuff
> any more. But you can run layers if you want.
Yes. As long as both ends are talking tcp/ip... :-)
JF Mezei
> Wyse 520 will support TD/SMP.
Pardon my ignorance here, but what is TD/SMP ?
On my TX ports on the VAX, I was never avle to have a VT terminal have
multiple sessions. I could have disconnected sessions, but not quickly
switch from one to another. So where is this VMS support people mention ?
Are there ANSI style escape sequences a terminal sends to a computer to
switch sessions, followed by an implicit <ctrl-W> to redraw the screen ?
I know that VT400 series terminals had multiple RS232 plugs and provided
a way to switch between RS232 sessions (complete with local memory of
the scxreen display for each session. But this wouldn't need any support
from the OS.
And I know that terminal servers allowed multiple sessions to a
terminal, but required you press BREAK, followed by ATTACH xx to switch
from one session to the next (and there was no automatic redraw of the
screen).
So what exactly is that TD/SMP in relation to what I know ?
VAXman-
>Scott Dorsey wrote:
>> Keith F. Lynch <k...@KeithLynch.net> wrote:
>>> Bob Eager <rd...@spamcop.net> wrote:
>>>> Shells don't support these things. You wouldn't ask if DCL supported
>>>> it...!
>>> Sorry, I was clumsily trying to convey that I meant a shell host
>>> supporting multiple simultaneous sessions from a single terminal over
>>> a single RS-232 serial line using the TD/SMP protocol. As contrasted
>>> with a Linux (or whatever) machine running a terminal emulator.
>>
>> Wyse 520 will support TD/SMP. I think that's the only hardware terminal
>> that is currently manufactured which will support it. Lynwood used to
>> make a terminal emulator for the IBM PC that supported it, and I think
>> PCTerm supported it.
>
>Well, doh! Except of course for the VT520 and VT525, which are still
>manufactured.
>http://www.boundless.com/terminals.html
Thanks, I was going to reply and say that my VT525 does it. You beat
me to it.
Keith F. Lynch
> Pardon my ignorance here, but what is TD/SMP ?
Terminal Device/Session Management Protocol (TD/SMP) is a protocol
that allows two terminal sessions to run simultaneously over one
RS-232 serial line. On the VT420, you can either split one screen or
switch between two screens with the <F4> key. And you can either use
TD/SMP to have two sessions, or you can use the terminal's second
serial port for the second session.
(I used to have my VT420 set up to use the second screen and second
serial port to connect to my PC. (The first port connects to my
modem.) But now, to save on my electric bill, I usually leave the PC
powered down and have the second screen in local mode, where it makes
a handy, albeit small, scratchpad that I can and paste to and from.
Right now it contains a list of message numbers I intend to reply to,
including this one.)
> Are there ANSI style escape sequences a terminal sends to a computer
> to switch sessions, followed by an implicit <ctrl-W> to redraw the
> screen ?
Not ANSI-style. And, if I recall correctly, they involve the
control-T character, not the escape character. But you have
the right general idea.
Keith F. Lynch
> A multidrop, in my parlance, is a connection where you have
> one-to-many/many-to-one. Usually together with some software
> protocol, to manage things so that noone gets confused.
> It usually takes a little wiring to get it sorted out as well, since
> you cannot have several transmitters active and wired together, to
> one receiver.
I have two VT420s in one "multidrop," such that anything from the
modem will appear on both at once (if they're both turned on), and I
can type on either one. The only non-trivial wiring was a pair of
diodes where the two transmit leads converge on the modem. To keep
things simple, I'm only using the transmit, receive, and ground leads.
This of course means that there's no hardware flow control. And since
I use Emacs, for which control-S and control-Q are commands, there's
no software flow control either. But so long as I keep the speed at
9600 bps, there's no need for flow control. And I can't read that
fast anyway, so there's no point in running any faster.
One of the two VT420 terminals is in front of my couch, on which
I sprawl while posting, using postures that would make any typing
teacher despair. (But I have no hand or wrist problems after writing
and posting tens of thousand of messages, so I must be doing something
right.) The other terminal is over my treadmill, on which I briskly
walk uphill while reading large numbers of posts, marking some for
later reply.
A third VT420 terminal, not part of this setup, is on top of a DEC
Alpha, which in turn is on top of a VAX. (When my employer was short
of cash, they paid me in hardware.)
You can see photos of my setup at http://KeithLynch.net/pics/
Johnny Billquist
> Johnny Billquist <b...@softjar.se> wrote:
>> A multidrop, in my parlance, is a connection where you have
>> one-to-many/many-to-one. Usually together with some software
>> protocol, to manage things so that noone gets confused.
>
>> It usually takes a little wiring to get it sorted out as well, since
>> you cannot have several transmitters active and wired together, to
>> one receiver.
>
> I have two VT420s in one "multidrop," such that anything from the
> modem will appear on both at once (if they're both turned on), and I
> can type on either one. The only non-trivial wiring was a pair of
> diodes where the two transmit leads converge on the modem. To keep
> things simple, I'm only using the transmit, receive, and ground leads.
Yes, that is what I'd call multidrop. :-)
Your diodes is a solution to the multiple transmitter problem I was
talking about.
If you have open collector outputs you can solve it with a pullup (or
pulldown) as well.
> This of course means that there's no hardware flow control. And since
> I use Emacs, for which control-S and control-Q are commands, there's
> no software flow control either. But so long as I keep the speed at
> 9600 bps, there's no need for flow control. And I can't read that
> fast anyway, so there's no point in running any faster.
DEC never supported hardware flow control anyway, so that isn't much of
an issue (RS-232 don't even really have hardware flow control).
But with multidrop, you'll have a hard time with any flow control anyway.
> One of the two VT420 terminals is in front of my couch, on which
> I sprawl while posting, using postures that would make any typing
> teacher despair. (But I have no hand or wrist problems after writing
> and posting tens of thousand of messages, so I must be doing something
> right.) The other terminal is over my treadmill, on which I briskly
> walk uphill while reading large numbers of posts, marking some for
> later reply.
That solves the problem with potentially both terminals sending at the
same time. Physical limitations. You can only be at one place at a time. :-)
> A third VT420 terminal, not part of this setup, is on top of a DEC
> Alpha, which in turn is on top of a VAX. (When my employer was short
> of cash, they paid me in hardware.)
:-)
Michael Unger
On 2010-03-15 22:33, "VAXman- @SendSpamHere.ORG" wrote:
> In article <hnljqq$s8d$1...@Iltempo.Update.UU.SE>, Johnny Billquist <b...@softjar.se> writes:
>>Scott Dorsey wrote:
>> [...]
>>
>>Well, doh! Except of course for the VT520 and VT525, which are still
>>manufactured.
>>http://www.boundless.com/terminals.html
>
> Thanks, I was going to reply and say that my VT525 does it. You beat
> me to it.
On the Boundless website there is a note saying "Display: any SVGA
monitor, LCD displays in 80-column mode only. [...]" What are you using
-- CRT or LCD? Do you happen to know the reason for this limitation?
Michael
[1] <http://www.boundless.com/terminals.html>
[2] <http://www.boundless.com/specsheets/VT525%20Spec.pdf>
--
Real names enhance the probability of getting real answers.
My e-mail account at DECUS Munich is no longer valid.
VAXman-
>[Posting restricted to "comp.sys.dec" and "comp.os.vms" newsgroups]
>
>
>On 2010-03-15 22:33, "VAXman- @SendSpamHere.ORG" wrote:
>
>> In article <hnljqq$s8d$1...@Iltempo.Update.UU.SE>, Johnny Billquist <b...@softjar.se> writes:
>>>Scott Dorsey wrote:
>>> [...]
>>>
>>>Well, doh! Except of course for the VT520 and VT525, which are still
>>>manufactured.
>>>http://www.boundless.com/terminals.html
>>
>> Thanks, I was going to reply and say that my VT525 does it. You beat
>> me to it.
>
>On the Boundless website there is a note saying "Display: any SVGA
>monitor, LCD displays in 80-column mode only. [...]" What are you using
>-- CRT or LCD? Do you happen to know the reason for this limitation?
The d|i|g|i|t|a|l VT525 is a small box that looks like the Multia (I
think that was it) Alpha. I'm using it with a d|i|g|i|t|a|l VRT17-HA
and I see 80 and 132 column modes without issue.
John Wallace
wrote:
> [Posting restricted to "comp.sys.dec" and "comp.os.vms" newsgroups]
>
> On 2010-03-15 22:33, "VAXman- @SendSpamHere.ORG" wrote:
>
> >>Scott Dorsey wrote:
> >> [...]
>
> >>Well, doh! Except of course for the VT520 and VT525, which are still
> >>manufactured.
> >>http://www.boundless.com/terminals.html
>
> > Thanks, I was going to reply and say that my VT525 does it. You beat
> > me to it.
>
> On the Boundless website there is a note saying "Display: any SVGA
> monitor, LCD displays in 80-column mode only. [...]" What are you using
> -- CRT or LCD? Do you happen to know the reason for this limitation?
>
> Michael
>
> [1] <http://www.boundless.com/terminals.html>
> [2] <http://www.boundless.com/specsheets/VT525%20Spec.pdf>
>
> --
> Real names enhance the probability of getting real answers.
> My e-mail account at DECUS Munich is no longer valid.
How many horizontal pixels do you need for a VT525 in 132-column mode?
I can't remember what the VT525 font size was in pixels, and the
Boundless site doesn't make it obvious, but I'd bet at least 5 british
pennies that a generic SVGA LCD runs out of horizontal pixels in 132-
character mode and will therefore be basically unreadable - it's
probably just about OK on a basic SVGA CRT though.
Other suggestions welcome.
Michael Unger
> How many horizontal pixels do you need for a VT525 in 132-column mode?
> I can't remember what the VT525 font size was in pixels, and the
> Boundless site doesn't make it obvious, but I'd bet at least 5 british
> pennies that a generic SVGA LCD runs out of horizontal pixels in 132-
> character mode and will therefore be basically unreadable - it's
> probably just about OK on a basic SVGA CRT though.
>
> Other suggestions welcome.
Considering a 5x8 minimum size of a character and one dot space between
characters a 132 character display would be 791 pixels wide -- which
should be adequate with a 800x600 (SVGA) monitor.
Michael
JF Mezei
> DEC never supported hardware flow control anyway, so that isn't much of
> an issue (RS-232 don't even really have hardware flow control).
SET TERM/MODEM and SET TERM/COMMSYNC handled RTS/CTS flow control. 5.5-2
would have had that because this is when I had dial-up modems on my all
mighty microvax II with DHQ-11 Q-bus boards with 8 serial ports each.
Terminal servers with modem support also supported hardware flow control.
Keith F. Lynch
> DEC never supported hardware flow control anyway, so that isn't much
> of an issue (RS-232 don't even really have hardware flow control).
Then why does the VT420 have "Data Leads" versus "Only Modem Control"
as options? And why do the RS-423 connectors on the back of the
terminal have Data Set Ready and Data Terminal Ready pins?
(RS-232, a superset of RS-423, has both of those and also has Request
To Send and Clear To Send.)
> That solves the problem with potentially both terminals sending at
> the same time. Physical limitations. You can only be at one place
> at a time. :-)
I've tried typing on both terminals at once (the keyboard cords will
reach). Collisions are pretty rare even when I try to cause them.
That's because at 9600 bps each character takes about a thousandth of
a second to send. Two characters typed during the same second have
only one chance in a thousand of overlapping.
>> A third VT420 terminal, not part of this setup, is on top of a DEC
>> Alpha, which in turn is on top of a VAX. (When my employer was
>> short of cash, they paid me in hardware.)
> :-)
Unfortunately, that was my last IT job. I've been trying to get back
into the field ever since. But the jobs are *gone*. Maybe I should
move to India.
glen herrmannsfeldt
> Johnny Billquist <b...@softjar.se> wrote:
>> DEC never supported hardware flow control anyway, so that isn't much
>> of an issue (RS-232 don't even really have hardware flow control).
> Then why does the VT420 have "Data Leads" versus "Only Modem Control"
> as options? And why do the RS-423 connectors on the back of the
> terminal have Data Set Ready and Data Terminal Ready pins?
Modem control is different from flow control. In the days of
half duplex modems, the terminal had the ability to do line
turnaround. The modem connection could only go one way at a
time, with "request to send" as a request to the modem.
Years later, these signals were used as flow control, especially
for serial printers which couldn't always print as fast as
the data came in.
-- glen
Richard B. Gilbert
Tell me about it! I've been looking since August of 2004. You can't
get a job as a system manager unless you know both MUMPS and Cache.
And maybe not even then!!
Fortunately, I'm old enough to retire. But I miss it. I enjoyed the
work. The big paycheck was nice too.
Johnny Billquist
Even with full duplex terminals, modem control have some meaning.
You (DEC) use it to see that there is anything connected on the other
side. No transmission or reception takes place if DCD isn't asserted.
And no transmission takes place if CTS isn't asserted.
However, when the terminal needs to stop the other end from
transmitting, it does not play with the modem signals, but sends XOFF.
The same for the computer.
But that's what the "Modem signals" vs. "data leads only" signify. Will
the terminal check for a presence on the other side, or not.
Oh! I almost forgot. And on DEC OSes, if you have modem signals enabled,
you will be logged out if DCD is lost.
*Some* DEC terminals can be setup to play with the modem signals
instead, to be compatible with various equipment who breaks the
standard, but DEC operating systems never do that.
So XON/XOFF flow control it is.
Johnny Billquist
> Johnny Billquist <b...@softjar.se> wrote:
>> DEC never supported hardware flow control anyway, so that isn't much
>> of an issue (RS-232 don't even really have hardware flow control).
>
> Then why does the VT420 have "Data Leads" versus "Only Modem Control"
> as options? And why do the RS-423 connectors on the back of the
> terminal have Data Set Ready and Data Terminal Ready pins?
>
> (RS-232, a superset of RS-423, has both of those and also has Request
> To Send and Clear To Send.)
What does that have to do with hardware flow control???
Modem control is not the same thing as hardware flow control.
>> That solves the problem with potentially both terminals sending at
>> the same time. Physical limitations. You can only be at one place
>> at a time. :-)
>
> I've tried typing on both terminals at once (the keyboard cords will
> reach). Collisions are pretty rare even when I try to cause them.
> That's because at 9600 bps each character takes about a thousandth of
> a second to send. Two characters typed during the same second have
> only one chance in a thousand of overlapping.
Well, technically, a character will take about 1/100 of a second to
transmit, but that still makes it tricky to make both terminals transmit
at exactly the same time.
>>> A third VT420 terminal, not part of this setup, is on top of a DEC
>>> Alpha, which in turn is on top of a VAX. (When my employer was
>>> short of cash, they paid me in hardware.)
>
>> :-)
>
> Unfortunately, that was my last IT job. I've been trying to get back
> into the field ever since. But the jobs are *gone*. Maybe I should
> move to India.
There are still plenty of IT jobs all around the world... The question
is if they interesting enough.
Bill Gunshannon
"Keith F. Lynch" <k...@KeithLynch.net> writes:
>
> Unfortunately, that was my last IT job. I've been trying to get back
> into the field ever since. But the jobs are *gone*. Maybe I should
> move to India.
What do you mean "the jobs are gone"? I can point you at hundreds if
not thousands of IT jobs. Or do you equate IT only with VMS? In which
case, yes, you are right.
bill
--
Bill Gunshannon | de-moc-ra-cy (di mok' ra see) n. Three wolves
bill...@cs.scranton.edu | and a sheep voting on what's for dinner.
University of Scranton |
Scranton, Pennsylvania | #include <std.disclaimer.h>
JF Mezei
> Modem control is not the same thing as hardware flow control.
Equipment equipped to support modems almost always also have support for
RTS/CTS along with all the other lines used by modems.
And when modems started to have variable speeds that did not match RS232
speeds, hardware flow control with RTS/CTS was the only truly reliable
means of connecting modems, especially with systems like VMS that used
XON-XOFF between the terminal and the host (thus needing a transparent
link).
Bill Gunshannon
It's deja vu all over again..... We just went thru this whole
discussion a short time ago. Even I accepted that there is no
formal hardware flow control but many systems implemented it
using modem control. Maybe we should all write it up and submit
it for formal acceptance by some standards body!!
JF Mezei
> It's deja vu all over again..... We just went thru this whole
> discussion a short time ago. Even I accepted that there is no
> formal hardware flow control but many systems implemented it
> using modem control.
SET
TERMINAL
/COMMSYNC
/COMMSYNC
/NOCOMMSYNC (default)
Allows connection of asynchronous printers and other devices
to terminal ports, using standard modem control signals as flow
control. Transmission to the device stops if either data set
ready (DSR) or clear to send (CTS) EIA modem control signals are
dropped. Transmission resumes when both signals are present.
The /COMMSYNC qualifier and the /MODEM qualifier are mutually
exclusive.
The COMMSYNC feature has the following limitations:
o Cannot be used on LAT ports
o Can only be used on ports with full modem control
o Should not be used in conjunction with Xon/Xoff flow control
(the port may hang)
CAUTION
The /COMMSYNC qualifier should never be set on a line with
a modem that is intended for interactive use. The qualifier
disables the modem terminal characteristic that disconnects
a user process from the terminal line in case of a modem
phone line failure. With the /COMMSYNC qualifier enabled,
the next call on the terminal line could be attached to the
previous user's process. Security administrators should
be aware that the characteristic should not be used on
interactive terminal ports. In addition, the /COMMSYNC
qualifier is not supported on a port connected to a LAT
line.
Keith F. Lynch
> What do you mean "the jobs are gone"? I can point you at hundreds
> if not thousands of IT jobs.
Gone from the Washington DC area, traditionally claimed to be
recession-proof, anyway, if you exclude jobs that require a high
level security clearance.
Okay, there are a few, but they all require, not just knowledge of
some new programming language, but recent paid experience in it. With
over a dozen people who match every requirement in the ad, no matter
how arbitrary, employers can afford to be picky.
Keith F. Lynch
> Keith F. Lynch wrote:
>> I've tried typing on both terminals at once (the keyboard cords
>> will reach). Collisions are pretty rare even when I try to cause
>> them. That's because at 9600 bps each character takes about a
>> thousandth of a second to send. Two characters typed during the
>> same second have only one chance in a thousand of overlapping.
> Well, technically, a character will take about 1/100 of a second to
> transmit, ...
How do you figure that? 9600 bits per second, with eight data bits,
one start bit, and one stop bit per character, means 960 characters
per second, or 1/960 second per character.
> There are still plenty of IT jobs all around the world...
I'd rather stay out of IT than relocate, as my family and friends
are very important to me.
> The question is if they interesting enough.
I don't work in order to be entertained. I'm perfectly willing to do
tedious things.
Johnny Billquist
> Johnny Billquist <b...@softjar.se> wrote:
>> Keith F. Lynch wrote:
>>> I've tried typing on both terminals at once (the keyboard cords
>>> will reach). Collisions are pretty rare even when I try to cause
>>> them. That's because at 9600 bps each character takes about a
>>> thousandth of a second to send. Two characters typed during the
>>> same second have only one chance in a thousand of overlapping.
>
>> Well, technically, a character will take about 1/100 of a second to
>> transmit, ...
>
> How do you figure that? 9600 bits per second, with eight data bits,
> one start bit, and one stop bit per character, means 960 characters
> per second, or 1/960 second per character.
Doh! Ok. Call me an idiot. I can't count. :-)
(For some reason my brain said 9600/10 means about 100 last night.)
>> There are still plenty of IT jobs all around the world...
>
> I'd rather stay out of IT than relocate, as my family and friends
> are very important to me.
That is always a problem. I guess depending on where you live, it might
be difficult to find work locally. But there are definitely still plenty
of work in the IT industry in the western world. But the US is a big
place, so that could still mean relocating.
>> The question is if they interesting enough.
>
> I don't work in order to be entertained. I'm perfectly willing to do
> tedious things.
Tricky, though. It helps, in the long run, to do something that you
enjoy doing. But I'm not one to say your attitude is wrong.
I wish you good luck!
Bill Gunshannon
"Keith F. Lynch" <k...@KeithLynch.net> writes:
>> What do you mean "the jobs are gone"? I can point you at hundreds
>> if not thousands of IT jobs.
>
> Gone from the Washington DC area,
Say what? I see hundreds every day.
> traditionally claimed to be
> recession-proof, anyway, if you exclude jobs that require a high
> level security clearance.
Any reason why? It costs you nothing as your employer picks up the
tab. And if your concerned about the investigation, most non-security
clearance jobs require an equivalent investigation. Unless your dream
job is something like janitor or grounds-keeper.
>
> Okay, there are a few, but they all require, not just knowledge of
> some new programming language, but recent paid experience in it.
Not all IT jobs require programming at all. There are many other
facets of this industry. IA, networking. And a lot of them are
interesting and even, in some cases, fun.
> With
> over a dozen people who match every requirement in the ad, no matter
> how arbitrary, employers can afford to be picky.
Believe it or not, for many getting your foot int he door is more about
writing skills than IT qualifications. And once you get to the interview
it's all about salesmanship.
You didn't give specifics about where in the DC area but a quick
search of just one employer returned ~50 jobs in the Maryland/Virgina
area and that was from just one employer. I am aware of a large
number of openings with a different employer just south of Baltimore.
I would need more info (that you might not be willing to provide and
certainly not publicly) but I could probably point you in the direction
of some promising career opportunities. (I do this for our students all
the time.)
Richard B. Gilbert
> In article <hns3h2$lot$2...@reader1.panix.com>,
> "Keith F. Lynch" <k...@KeithLynch.net> writes:
>> Bill Gunshannon <bill...@cs.uofs.edu> wrote:
>>> What do you mean "the jobs are gone"? I can point you at hundreds
>>> if not thousands of IT jobs.
>> Gone from the Washington DC area,
>
> Say what? I see hundreds every day.
>
>> traditionally claimed to be
>> recession-proof, anyway, if you exclude jobs that require a high
>> level security clearance.
>
> Any reason why? It costs you nothing as your employer picks up the
> tab. And if your concerned about the investigation, most non-security
> clearance jobs require an equivalent investigation. Unless your dream
> job is something like janitor or grounds-keeper.
>
In the days when I held a Top Secret clearance, it required a full
background investigation! The FBI visited every place you had ever
lived, asked the neighbors about your affiliations, etc. It took four
to six months to do it. I've no idea what it cost but it can't be cheap!
Bill Gunshannon
"Richard B. Gilbert" <rgilb...@comcast.net> writes:
> Bill Gunshannon wrote:
>> In article <hns3h2$lot$2...@reader1.panix.com>,
>> "Keith F. Lynch" <k...@KeithLynch.net> writes:
>>> Bill Gunshannon <bill...@cs.uofs.edu> wrote:
>>>> What do you mean "the jobs are gone"? I can point you at hundreds
>>>> if not thousands of IT jobs.
>>> Gone from the Washington DC area,
>>
>> Say what? I see hundreds every day.
>>
>>> traditionally claimed to be
>>> recession-proof, anyway, if you exclude jobs that require a high
>>> level security clearance.
>>
>> Any reason why? It costs you nothing as your employer picks up the
>> tab. And if your concerned about the investigation, most non-security
>> clearance jobs require an equivalent investigation. Unless your dream
>> job is something like janitor or grounds-keeper.
>>
>
> In the days when I held a Top Secret clearance,
If you already had a clearance barring any disqualifying events :-)
it is much easier to just get it back. Wend I went back into the
military (PAARNG) in 2003 it took about 4 months to get my Secret
clearance back. When they decided I need a TS it took about another
6 months and most of that was the delay in catching up to and
interviewing me.
> it required a full
> background investigation!
If you had one already it usually just takes going back to that point.
> The FBI visited every place you had ever
> lived, asked the neighbors about your affiliations, etc.
Yeah, well it gives all those field agents something to do. And, actually,
much of it is done by contractors today.
> It took four
> to six months to do it.
And, unless you know there is something in your past to make you
inelligible for a security clearance you don't even have to wait
until you have one to apply for the jobs. They can (and will) hire
you and then get you your clearance after the fact. Having had
one in the past you could probably have an Interim Secret in a
couple of weeks. Now, going to work for a Contractor may be differnt.
But I have less experience with that side of the coin.
> I've no idea what it cost but it can't be cheap!
It costs the same wether they are doing it for you or someone else
so there is no reason you should let the cost affect your decision
about seeking this kind of job.
Scott Dorsey
>
>In the days when I held a Top Secret clearance, it required a full
>background investigation! The FBI visited every place you had ever
>lived, asked the neighbors about your affiliations, etc. It took four
>to six months to do it. I've no idea what it cost but it can't be cheap!
It's much worse now than it was even ten years ago.... in the post-911
world, it can take a couple years to get a clearance through. Consequently,
companies that used to be willing to just hire someone and wait until their
clearance was processed are now only willing to hire people with already
active clearances.
This has become a serious problem for folks in the DC area; you are locked
out of a lot of jobs without a clearance, but yet you cannot get a clearance
without a job.
Still, there are people out there who have pissed off too many of the "ants"
who might be offering them jobs, and who consequently are less apt to get
employment in the area.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Keith F. Lynch
> It's much worse now than it was even ten years ago.... in the
> post-911 world, it can take a couple years to get a clearance
> through.
Indeed. My brother gave up after waiting *over a year* for a
*confidential* clearance, which used to be almost instant. This was
in 2002-2003. And he has never been arrested or hospitalized, never
been a member of any remotely controversial organization, never been
Muslim or Communist, has lived in the same county since he was an
infant, and at the time had never traveled overseas or had any foreign
friends. Sheesh!
> Consequently, companies that used to be willing to just hire someone
> and wait until their clearance was processed are now only willing to
> hire people with already active clearances.
Yes. There are numerous job ads, job websites, and job fairs that
are only for people who already have clearances. Why not, in this
economy, when there are at least a dozen fully qualified applicants
for every job? Anyone who needs clearing, needs training, has ever
been arrested, or has any gaps on their resume can forget it.
> This has become a serious problem for folks in the DC area; you are
> locked out of a lot of jobs without a clearance, but yet you cannot
> get a clearance without a job.
Quite so, but that's not the issue in my case. 33 years ago I was
falsely convicted of breaking into an office. My record is perfectly
clear before and since. And indeed I got a clearance just five years
later, albeit after explaining the circumstances of my conviction
at great length. However, in 2000 the Smith Amendment permanently
revoked the clearances of everyone who had ever been convicted of any
felony, ever, regardless of circumstances.
I've often wondered if it was a coincidence that 9/11 happened the
following year. Perhaps the people who would have detected and
prevented that terrorist plot were flipping burgers or greeting
Wal-Mart customers instead, as the public had been protected against
them in yet another of America's many shameful moral panics.
Bill Pechter
Ah yes... Heard from my neighbors and parents neighbors when I got
cleared in the 80's and early 90's.
Expensive process -- which is why they now try to hire cleared personnel
first rather than hiring someone to sit in a corner until the clearance
comes through. Went through this at Fort Monmouth a couple of times.
I spent months telling another person what to type as root on a Unix box
to fix the problem.
Most places up here don't even want to interview unless you have an
active clearance or if they are desperate.
(Especially since Ft. Monmouth goes bye-bye next year. Along with the
jobs. Just like Bell Labs Holmdel and much of AT&T. Used to be I
couldn't spit in Monmouth county without hitting an open sysadmin job...)
8-(
--
"When I think back on all the crap I learned in Vax school
It's a wonder I fixed anything at all." (to the tune of Kodachrome)
pechter-at-ureach.com
VAXman-
Been there. Done that. Got the T-shirt.
I spent several years at both Lakehurst NAEC and the Hex at Ft. Monmouth.
I can't believe that Ft. Monmouth was to be closed over Lakehurst. The
ONLY thing I can see is that that part of proNJ thrives on the money that
Uncle Sam pumps into Lakehurst. Short of its historical significance, I
only saw there what we used to refer to a "middle-class welfare". People
who couldn't get jobs in the real work-force were propped up by salaries
issued to them on a GS engineering scale. Most of those GS engineers had
difficulty figuring out which end of a screwdriver to use to drive a nail.
On the other end of the spectrum, I worked with quite a few Ph.Ds in the
Hex. One of them I graduated college with and he went on to get the full
alphabet soup on Uncle Sam's dime. Closing those facilities not only did
a disservice to those working there but also to the American taxpayer that
paid for many of those people to get post-graduate and doctorate degrees.
At Monmouth U., I had professors from Ft. Monmouth, AT&T, Bell Labs, FEL,
EAI, etc. There's none of these in the area any more and MU no longer has
any engineering program. MU has lots of business majors and MBAs now. No
more brains graduating there; only business bullies. :(
Bill, we should meet up some day an discuss old war stories about common
stomping grounds.