Problem Using a Commodore 1084s Monitor on a IIgs
Polymorph
If you've not been following another other thread that I started, my
daughters IIgs monitor died just before Christmas and I've been
attempting to repair it. Although I made it better, its still not
perfect.
Because of this I picked up a Commodore 1084s monitor off of eBay to
use as a replacement. I have tested the monitor with a DVD player and
the image produced was quite good, so I know the monitor is working.
However, I wired up a cable as per the Apple II FAQ over the weekend
and had troubles getting the monitor to synch with the RGB signal. The
image just kept scrolling all over the place. I tested the cable, and
everything seemed to be wired correctly.
In an attempt to fix the problem, I tried:
(i) to wire the IIgs's composite synch to the horizontal synch
(ii) switch the monitor between 50Hz and 60Hz
None of the above made any difference.
One thing I should note is that just about everywhere lists the 1084
monitors D-9 RGB connector as being female, however in the monitor I
have it is male. Consequently, my cable has a female D-9 socket. I
have made the assumption that the wiring would still be the same (i.e.
pin 1 mentioned in the A2 FAQ is pin 1 on my monitor). This seems to
be true as I do not think I would get the image that I am getting if
it were incorrect. It just seems to not be synching with the signal.
So I did some snooping around in the c.s.a2 newsgroups looking for
threads on using 1084 monitors with the IIgs. I found a post by Jeff
Blakeney in the mid-1990's mentioning the usage of a 75 Ohm resistor
wired between the composite synch and ground to alter the voltage to
more acceptable levels for the 1084 monitor. Most other posters using
a 1084 don't mention any requirement for doing this, and the Apple II
FAQ doesn't mention it either. But I plan on giving it a try once I
get a chance on getting to my local electronics dealer.
To gauge the likelihood of success, has anyone else had to use a 75
Ohm resistor in this manner to get a 1084 to synch with the IIgs? Is
there anything else I can try to get the image to synch?
Thanks,
Mike
fer...@gmx.de
If it is rolling up/down then you're lacking vertical sync. Otherwise
you're lacking horizontal sync.
Wiring Composite sync to Horizontal sync should give horizontal sync,
but there may or may not be vertical sync. One thing to try would be
to wire Composite sync to Horizontal AND vertical sync.
If there is no horizontal sync you either have a bad sync connection
(whereever... You didn't wire the DVD player to the DB9 input, did
you?), or the sync level is too low (AFAIK Commodore used TTL sync,
i.e. 3Vpp, but the IIgs uses only 0,7Vpp, however I'm not shure with
this.)
Does the 1084 have a switch to select analog or digital mode? If it
has it should be set to analog so that the monitor takes sync from the
composite sync input pin.
> One thing I should note is that just about everywhere lists the 1084
> monitors D-9 RGB connector as being female, however in the monitor I
> have it is male. Consequently, my cable has a female D-9 socket. I
> have made the assumption that the wiring would still be the same (i.e.
> pin 1 mentioned in the A2 FAQ is pin 1 on my monitor). This seems to
> be true as I do not think I would get the image that I am getting if
> it were incorrect. It just seems to not be synching with the signal.
You'll get that phenomenon if you just wired the sync incorrectly.
There is a trick to figure out the pinout: Use a jumper wire to join
the grounds of the Apple and the monitor. A good ground point is the
metallic part of the D-Sub connector.
Then start with the "red" signal and test every pin on the 1084 until
you get a red display. Solder it to the connector
Do the same with green (yellow display) and blue (white display).
Now take the sync pin and tap through the pins until you get a stable
display. Now turn the monitor of, and find the ground pins by
measuring the resistance to the metallic part of the D-Sub. If it is
<5 Ω, you have a ground.
----
Ferdinand
heuser...@freenet.de
>
> Because of this I picked up a Commodore 1084s monitor off of eBay to
> use as a replacement. I have tested the monitor with a DVD player and
> the image produced was quite good, so I know the monitor is working.
Via composite or via RGB?
> However, I wired up a cable as per the Apple II FAQ over the weekend
> and had troubles getting the monitor to synch with the RGB signal. The
> image just kept scrolling all over the place.
This really sounds like a sync problem.
> I tested the cable, and everything seemed to be wired correctly.
>
> In an attempt to fix the problem, I tried:
> (i) to wire the IIgs's composite synch to the horizontal synch
> (ii) switch the monitor between 50Hz and 60Hz
>
> None of the above made any difference.
>
> One thing I should note is that just about everywhere lists the 1084
> monitors D-9 RGB connector as being female, however in the monitor I
> have it is male. Consequently, my cable has a female D-9 socket. I
> have made the assumption that the wiring would still be the same (i.e.
> pin 1 mentioned in the A2 FAQ is pin 1 on my monitor). This seems to
> be true as I do not think I would get the image that I am getting if
> it were incorrect. It just seems to not be synching with the signal.
>
> So I did some snooping around in the c.s.a2 newsgroups looking for
> threads on using 1084 monitors with the IIgs. I found a post by Jeff
> Blakeney in the mid-1990's mentioning the usage of a 75 Ohm resistor
> wired between the composite synch and ground to alter the voltage to
> more acceptable levels for the 1084 monitor. Most other posters using
> a 1084 don't mention any requirement for doing this, and the Apple II
> FAQ doesn't mention it either.
>
> To gauge the likelihood of success, has anyone else had to use a 75
> Ohm resistor in this manner to get a 1084 to synch with the IIgs?
For a PAL monitor you don't need to do this.
> Is there anything else I can try to get the image to synch?
The standard way for a GS to connect to a PAL 1081/1084s
(the 1081 has mono sound, while the 1084 is stereo) is to use
its Euroscart input with its analog RGB leads.
Pin 3 ("composite sync") of the GS video output jack must be
fed into the composite video input of the Euroscart connector
(pin 20).
There is more to do with this type of connector - this page
details the pin to pin connections:
http://vintageware.orcon.net.nz/apple2/scart.html
Here you can download the PAL schematics of the 1081s which
may or may not be of help (be cautious because of the differences!):
http://rapidshare.de/files/38368884/Monitor_1081.zip.html
I would try to connect pin 3 of the GS output to the composite
input of your monitor.
If this doesn't work it could be a "sync-on-green" problem but
I'm not really familiar with this. I only wanted to throw this into
the room so somebody else can jump into it (or discard it).
HTH,
Marcus
Polymorph
On Jan 22, 1:17 am, ferd...@gmx.de wrote:
> Is the image rolling up and down or left/right?
It seems to be rolling in both directions - but its hard to make out
for sure.
> If it is rolling up/down then you're lacking vertical sync. Otherwise
> you're lacking horizontal sync.
> Wiring Composite sync to Horizontal sync should give horizontal sync,
> but there may or may not be vertical sync. One thing to try would be
> to wire Composite sync to Horizontal AND vertical sync.
> If there is no horizontal sync you either have a bad sync connection
> (whereever... You didn't wire the DVD player to the DB9 input, did
> you?), or the sync level is too low (AFAIK Commodore used TTL sync,
> i.e. 3Vpp, but the IIgs uses only 0,7Vpp, however I'm not shure with
> this.)
> Does the 1084 have a switch to select analog or digital mode? If it
> has it should be set to analog so that the monitor takes sync from the
> composite sync input pin.
It does have a switch, and yes I have selected analog mode.
> > One thing I should note is that just about everywhere lists the 1084
> > monitors D-9 RGB connector as being female, however in the monitor I
> > have it is male. Consequently, my cable has a female D-9 socket. I
> > have made the assumption that the wiring would still be the same (i.e.
> > pin 1 mentioned in the A2 FAQ is pin 1 on my monitor). This seems to
> > be true as I do not think I would get the image that I am getting if
> > it were incorrect. It just seems to not be synching with the signal.
>
> You'll get that phenomenon if you just wired the sync incorrectly.
> There is a trick to figure out the pinout: Use a jumper wire to join
> the grounds of the Apple and the monitor. A good ground point is the
> metallic part of the D-Sub connector.
> Then start with the "red" signal and test every pin on the 1084 until
> you get a red display. Solder it to the connector
> Do the same with green (yellow display) and blue (white display).
> Now take the sync pin and tap through the pins until you get a stable
> display. Now turn the monitor of, and find the ground pins by
> measuring the resistance to the metallic part of the D-Sub. If it is
> <5 Ù, you have a ground.
OK, I'll give that a try. So nobody can vouch for the addition of a 75
Ohm resistor between composite synch and ground?
Thanks for your help. :-)
I must admit, after reading all the descriptions floating around about
using 1084's with the IIgs I expected this to be a whole lot simpler.
cheers,
Mike
Polymorph
> Polymorph wrote:
>
> > Because of this I picked up a Commodore 1084s monitor off of eBay to
> > use as a replacement. I have tested the monitor with a DVD player and
> > the image produced was quite good, so I know the monitor is working.
>
> Via composite or via RGB?
Via composite only.
>
> > However, I wired up a cable as per the Apple II FAQ over the weekend
> > and had troubles getting the monitor to synch with the RGB signal. The
> > image just kept scrolling all over the place.
>
> This really sounds like a sync problem.
Thats what I reckon too... :-)
>
> For a PAL monitor you don't need to do this.
>
> > Is there anything else I can try to get the image to synch?
>
> The standard way for a GS to connect to a PAL 1081/1084s
> (the 1081 has mono sound, while the 1084 is stereo) is to use
> its Euroscart input with its analog RGB leads.
There is apparently many different connections available for the 1084
monitors and unfortunately mine does not have the SCART adapter. I
wish it did as I already own a IIgs --> SCART adapter from
Vintageware. The 1084 monitor I have only has the D-9 RGB connector +
the usual composite sockets.
>
> Pin 3 ("composite sync") of the GS video output jack must be
> fed into the composite video input of the Euroscart connector
> (pin 20).
Well, as per the Apple II FAQ, I have the composite synch wired up to
the composite synch of the D-9 connector (from memory I think its pin
7).
> There is more to do with this type of connector - this page
> details the pin to pin connections:http://vintageware.orcon.net.nz/apple2/scart.html
I bought one of Vintageware's cables a couple of years ago which was
connected to the monitor that died. As the new monitor doesn't have
SCART, its been made redundant until I can fix the original monitor.
> Here you can download the PAL schematics of the 1081s which
> may or may not be of help (be cautious because of the differences!):http://rapidshare.de/files/38368884/Monitor_1081.zip.html
>
> I would try to connect pin 3 of the GS output to the composite
> input of your monitor.
Yep, did that. That is as per the Apple II FAQ.
> If this doesn't work it could be a "sync-on-green" problem but
> I'm not really familiar with this. I only wanted to throw this into
> the room so somebody else can jump into it (or discard it).
Any comments on the usage of a 75 Ohm resistor between composite synch
and ground? I think I will try this anyway, as Jeff Blakeney has a
pretty good rep around the traps and I'm sure he wouldn't have said
that if it were'nt necessary for him. :-)
Thanks,
Mike
nyder
...
> OK, I'll give that a try. So nobody can vouch for the addition of a 75
> Ohm resistor between composite synch and ground?
>
> Thanks for your help. :-)
>
> I must admit, after reading all the descriptions floating around about
> using 1084's with the IIgs I expected this to be a whole lot simpler.
>
> cheers,
> Mike
To connect my Atari 1040ST to a 1084 monitor, i had to put a 50 ohm
resistor on both my horizontal and vertical sync.
Robert
heuser...@freenet.de
> On Jan 22, 4:51 am, heuser.mar...@freenet.de wrote:
>
> > Via composite or via RGB?
>
> Via composite only.
So you know that the monitor generally works but it won't
help you with the RGB connector. I asked, because in
Germany a lot of DVD players are connected via RGB
(Euroscart) because of the much better picture quality.
> There is apparently many different connections available
> for the 1084 monitors and unfortunately mine does not have
> the SCART adapter. I wish it did as I already own a IIgs -->
> SCART adapter from Vintageware. The 1084 monitor I have
> only has the D-9 RGB connector + the usual composite sockets.
But the inner workings on the signals should be very similar
for the analog RGB input - maybe somebody can get you the
schematics of your exact monitor.
> > Pin 3 ("composite sync") of the GS video output jack must be
> > fed into the composite video input of the Euroscart connector
> > (pin 20).
>
> Well, as per the Apple II FAQ, I have the composite synch
> wired up to the composite synch of the D-9 connector (from
> memory I think its pin 7).
Here's another possibility (though unlikely:
A defective connector jack with a broken pin.
I once had trouble with this 19 year old monitor and had to
resolder the composite connector pins because the solder
point on the printed board was defective.
> > I would try to connect pin 3 of the GS output to the composite
> > input of your monitor.
>
> Yep, did that. That is as per the Apple II FAQ.
So pin 7 on the monitor is not only the sync signal but also
a full composite input? This is the way the Euroscart models
work internally.
> Any comments on the usage of a 75 Ohm resistor between composite synch
> and ground?
Not necessary with the Euroscart models so I can't really
comment on that.
> I think I will try this anyway, as Jeff Blakeney has a
> pretty good rep around the traps and I'm sure he wouldn't have said
> that if it were'nt necessary for him. :-)
I don't know if this works but I don't see that it could break
anything.
bye
Marcus
Michael J. Mahon
>
>>OK, I'll give that a try. So nobody can vouch for the addition of a 75
>>Ohm resistor between composite synch and ground?
>>
>>Thanks for your help. :-)
>>
>>I must admit, after reading all the descriptions floating around about
>>using 1084's with the IIgs I expected this to be a whole lot simpler.
>>
>>cheers,
>>Mike
>
>
>
> To connect my Atari 1040ST to a 1084 monitor, i had to put a 50 ohm
> resistor on both my horizontal and vertical sync.
Since the wires are short (and not even coax), the 75 or 50 ohm resistor
is not important as a termination.
Therefore, it's primary function must be either: 1) to load the sync
line to reduce its level so that it does not overload the sync circuits
of the 1084, or 2) to provide a DC return for a capacitively coupled
sync signal (but in the latter case, a 4.7k resistor would work as
well, so perhaps not).
-michael
NadaPong: Network game demo for Apple II computers!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it's seriously underused."
Linards Ticmanis
> One thing I should note is that just about everywhere lists the 1084
> monitors D-9 RGB connector as being female, however in the monitor I
> have it is male. Consequently, my cable has a female D-9 socket. I
> have made the assumption that the wiring would still be the same (i.e.
> pin 1 mentioned in the A2 FAQ is pin 1 on my monitor). This seems to
> be true as I do not think I would get the image that I am getting if
> it were incorrect. It just seems to not be synching with the signal.
There were a whole bunch of slightly different makes of 1084, and at
least one version was *very* different from the others.
You should maybe ask Ray Carlsen on comp.sys.cbm, who is the
Internationally Accepted Guru (TM) for the finer points of Commodore
harwadare connectors, and also a pretty nice guy. He also has or (had) a
homepage somewhere with lots of info of that kind.
If your 1084 is not a 1084S (the S has stereo speakers) and it has a
covered hole on the back shaped like a SCART connector, the SCART is
fairly easy to retrofit. Connections are already on the PCB and all you
have to add besides the connector is something like two pieces of wire
and two resistors, all marked on the board IIRC. You will probably need
a schematic for this, though. The 1084S unfortunately uses the same area
of the PCB for connecting its stereo amplifier board, so it's not as
easy to convert to SCART as the plain 1084.
--
Linards Ticmanis
Polymorph
> Polymorph wrote:
> > One thing I should note is that just about everywhere lists the 1084
> > monitors D-9 RGB connector as being female, however in the monitor I
> > have it is male. Consequently, my cable has a female D-9 socket. I
> > have made the assumption that the wiring would still be the same (i.e.
> > pin 1 mentioned in the A2 FAQ is pin 1 on my monitor). This seems to
> > be true as I do not think I would get the image that I am getting if
> > it were incorrect. It just seems to not be synching with the signal.
>
> There were a whole bunch of slightly different makes of 1084, and at
> least one version was *very* different from the others.
>
> You should maybe ask Ray Carlsen on comp.sys.cbm, who is the
> Internationally Accepted Guru (TM) for the finer points of Commodore
> harwadare connectors, and also a pretty nice guy. He also has or (had) a
> homepage somewhere with lots of info of that kind.
OK, thanks for the heads up. I'll see if I can get in contact with
him.
> If your 1084 is not a 1084S (the S has stereo speakers) and it has a
> covered hole on the back shaped like a SCART connector, the SCART is
> fairly easy to retrofit. Connections are already on the PCB and all you
> have to add besides the connector is something like two pieces of wire
> and two resistors, all marked on the board IIRC. You will probably need
> a schematic for this, though. The 1084S unfortunately uses the same area
> of the PCB for connecting its stereo amplifier board, so it's not as
> easy to convert to SCART as the plain 1084.
Mine is a 1084S, and there is no covered hole for a SCART connector.
Thanks,
Mike
Jeff Blakeney
On Mon, 21 Jan 2008 14:23:36 -0800, Polymorph wrote:
> Any comments on the usage of a 75 Ohm resistor between composite synch
> and ground? I think I will try this anyway, as Jeff Blakeney has a
> pretty good rep around the traps and I'm sure he wouldn't have said
> that if it were'nt necessary for him. :-)
Sorry I haven't jumped in sooner but I fell behind on my newsgroup
reading this week. If I remember correctly, I had added the 75 Ohm
resistor to try to match the termination expected by the 1084S. After
posting about my wiring someone else mentioned that they either didn't
need it for theirs or didn't think it was required and sure enough, my
current IIgs 1084S monitor cable no longer has a 75 Ohm resistor on it
and it works fine.
By the way, my having a good rep around here depends a lot on who you
are talking to. :-)
--- Synchronet 3.14a-Win32 NewsLink 1.85
A2Central.com - Your total source for Apple II computing.
Polymorph
<jeff.blake...@a2central.com.remove-sd5-this> wrote:
> Sorry I haven't jumped in sooner but I fell behind on my newsgroup
> reading this week. If I remember correctly, I had added the 75 Ohm
> resistor to try to match the termination expected by the 1084S. After
> posting about my wiring someone else mentioned that they either didn't
> need it for theirs or didn't think it was required and sure enough, my
> current IIgs 1084S monitor cable no longer has a 75 Ohm resistor on it
> and it works fine.
Jeff, is the 1084S monitor you are using now the same monitor that you
had in the mid 90's? Here are the posts you made back then:
and
> By the way, my having a good rep around here depends a lot on who you
> are talking to. :-)
Oh well, I think that's pretty much true for all of us. All you can
really hope for is at least one person who thinks you know what you're
talking about... anything more than that is a bonus. :-)
cheers,
Mike
Polymorph
> On Jan 25, 12:02 am, "Jeff Blakeney"
>
> <jeff.blake...@a2central.com.remove-sd5-this> wrote:
> > Sorry I haven't jumped in sooner but I fell behind on my newsgroup
> > reading this week. If I remember correctly, I had added the 75 Ohm
> > posting about my wiring someone else mentioned that they either didn't
> > need it for theirs or didn't think it was required and sure enough, my
> > and it works fine.
I've been really busy the last few weeks and had put this project on
hold, however, I finally got around to trying Jeff's suggestion from
1995 and have put a 75 Ohm resistor between composite synch and ground
and he was definately onto something. Instead of seeing a fast
scrolling mess, it was possible to fine tune the vertical hold to
produce the pictures below:
http://apple2.sytes.net/DSC00042.JPG
http://apple2.sytes.net/DSC00046.JPG
Now, as you can see from the above images, it doesn't appear to be
fully synched. All the characters are leaning to the right (like
everything is in italics), and you can see the black area on the RHS
of the screen which is wobbling around a bit.
I'm thinking that in my case, 75 Ohms is not quite right, but
something in the vacinity would be right. Does this sound plausible?
Do you recommend that I buy a variable resistor and try and find the
optimum value? Or should I being trying something else.
With the results I've achieved thus far, it would seem that this is
going to work with a bit more messing around.
What would you guys recommend as the next course of action? All
comments welcome.
Cheers,
Mike
Michael J. Mahon
> On Jan 25, 9:43 am, Polymorph <polymorp...@hotmail.com> wrote:
>
>>On Jan 25, 12:02 am, "Jeff Blakeney"
>>
>><jeff.blake...@a2central.com.remove-sd5-this> wrote:
>>
>>>Sorry I haven't jumped in sooner but I fell behind on my newsgroup
>>>reading this week. If I remember correctly, I had added the 75 Ohm
>>>resistor to try to match the termination expected by the1084S. After
>>>posting about my wiring someone else mentioned that they either didn't
>>>need it for theirs or didn't think it was required and sure enough, my
>>>current IIgs1084Smonitor cable no longer has a 75 Ohm resistor on it
>>>and it works fine.
>
>
> I've been really busy the last few weeks and had put this project on
> hold, however, I finally got around to trying Jeff's suggestion from
> 1995 and have put a 75 Ohm resistor between composite synch and ground
> and he was definately onto something. Instead of seeing a fast
> scrolling mess, it was possible to fine tune the vertical hold to
> produce the pictures below:
>
> http://apple2.sytes.net/DSC00042.JPG
> http://apple2.sytes.net/DSC00046.JPG
So it appears that the IIgs was overdriving the 1084's sync input.
> Now, as you can see from the above images, it doesn't appear to be
> fully synched. All the characters are leaning to the right (like
> everything is in italics), and you can see the black area on the RHS
> of the screen which is wobbling around a bit.
This means that the horizontal sync is not quite right, either.
You could adjust the horizontal sync on the monitor to get it
closer, or....
> I'm thinking that in my case, 75 Ohms is not quite right, but
> something in the vacinity would be right. Does this sound plausible?
> Do you recommend that I buy a variable resistor and try and find the
> optimum value? Or should I being trying something else.
Exactly. Try lowering the value (or, better, adding a 75 to 150 Ohm
pot with the IIgs driving the "high" end and the output to the monitor
coming from the center terminal) until you can find where the sync
drops out because the level is too *low*. Then increase it until good
lock is achieved.
You may still find it worthwhile to adjust the vertical and horizontal
hold controls to the middle of their stable ranges. It seems that
this monitor's settings may have drifted a bit.
> With the results I've achieved thus far, it would seem that this is
> going to work with a bit more messing around.
>
> What would you guys recommend as the next course of action? All
> comments welcome.
You're almost there!
Neon Forests
This was a very common problem with RGB monitors in the old days.
I have no idea what the Commodore used, but there were basically two
sync standards back then (in addition to sync on green, which aided
color monitor usage on some black and white sources.)
To invert sync though, one either needs an IC or transistor (and some
resistors) and this can get messy.
Past that, your monitor might be broken too. It did come from Ebay...
;-)
Polymorph
> Polymorph wrote:
> > Now, as you can see from the above images, it doesn't appear to be
> > fully synched. All the characters are leaning to the right (like
> > everything is in italics), and you can see the black area on the RHS
> > of the screen which is wobbling around a bit.
>
> This means that the horizontal sync is not quite right, either.
> You could adjust the horizontal sync on the monitor to get it
> closer, or....
Michael, as per all of the IIgs-->1084 FAQs suggest, I've only
connected the composite sync from the IIgs to the composite sync of
the 1084. Also note that in the 1084 the composite sync and horizontal
sync are tied together (the 1084S-D schematic I found confirms this).
I have left the vertical sync not connected as per the Apple II FAQ.
> > I'm thinking that in my case, 75 Ohms is not quite right, but
> > something in the vacinity would be right. Does this sound plausible?
> > Do you recommend that I buy a variable resistor and try and find the
> > optimum value? Or should I being trying something else.
>
> Exactly. Try lowering the value (or, better, adding a 75 to 150 Ohm
> pot with the IIgs driving the "high" end and the output to the monitor
> coming from the center terminal) until you can find where the sync
> drops out because the level is too *low*. Then increase it until good
> lock is achieved.
Just so I am clear, when you say "lowering the value" do you mean the
voltage on the composite sync - i.e. lowering the resistor value used?
If that is the case, wouldn't I need a resistance of less than 75
Ohms, meaning a 75 to 100 Ohm pot would be too much resistance? Please
forgive me if I'm talking rubbish. ;-)
I took a look at the catalog of my local electronics dealer (Jaycar),
and they have a variable 0-200 Ohm variable resistor (this is the
smallest variable resistor they have). I'm thinking one of these
would fit the bill, what do you reckon?
> You may still find it worthwhile to adjust the vertical and horizontal
> hold controls to the middle of their stable ranges. It seems that
> this monitor's settings may have drifted a bit.
The vertical hold was very difficult to adjust to get the image to
stop rolling - i.e. there is a *very* small stable range for the
vertical hold. But it was possible, as the images I posted previously
confirm. I am guessing with a different resistor value this problem
will rectify itself. This problem with vertical hold was only present
using the RGB port however, when I hooked a DVD player up to it via
the composite ports I had no such problem.
> > What would you guys recommend as the next course of action? All
> > comments welcome.
>
> You're almost there!
Great! I was hoping you'd say that. ;-)
Thanks for your help,
Mike
Michael J. Mahon
> On Feb 11, 6:32 am, "Michael J. Mahon" <mjma...@aol.com> wrote:
>
>>Polymorph wrote:
>>
>>>Now, as you can see from the above images, it doesn't appear to be
>>>fully synched. All the characters are leaning to the right (like
>>>everything is in italics), and you can see the black area on the RHS
>>>of the screen which is wobbling around a bit.
>>
>>This means that the horizontal sync is not quite right, either.
>>You could adjust the horizontal sync on the monitor to get it
>>closer, or....
>
>
> Michael, as per all of the IIgs-->1084 FAQs suggest, I've only
> connected the composite sync from the IIgs to the composite sync of
> the 1084. Also note that in the 1084 the composite sync and horizontal
> sync are tied together (the 1084S-D schematic I found confirms this).
> I have left the vertical sync not connected as per the Apple II FAQ.
I wasn't referring to the horizontal sync input, but to the horizontal
sync (or "hold") adjustment on the monitor. This may be internal, or
accessible only through use of an "alignment tool" through a hole in
the back or bottom of the case. Ideally, it would be an external
control like the vertical hold control.
>>>I'm thinking that in my case, 75 Ohms is not quite right, but
>>>something in the vacinity would be right. Does this sound plausible?
>>>Do you recommend that I buy a variable resistor and try and find the
>>>optimum value? Or should I being trying something else.
>>
>>Exactly. Try lowering the value (or, better, adding a 75 to 150 Ohm
>>pot with the IIgs driving the "high" end and the output to the monitor
>>coming from the center terminal) until you can find where the sync
>>drops out because the level is too *low*. Then increase it until good
>>lock is achieved.
>
>
> Just so I am clear, when you say "lowering the value" do you mean the
> voltage on the composite sync - i.e. lowering the resistor value used?
> If that is the case, wouldn't I need a resistance of less than 75
> Ohms, meaning a 75 to 100 Ohm pot would be too much resistance? Please
> forgive me if I'm talking rubbish. ;-)
>
> I took a look at the catalog of my local electronics dealer (Jaycar),
> and they have a variable 0-200 Ohm variable resistor (this is the
> smallest variable resistor they have). I'm thinking one of these
> would fit the bill, what do you reckon?
A 200 Ohm pot is perfect. Actually, I hope it's a carbon pot, not
a wirewound pot. Low resistance pots may be wirewound, and the
inductance of the winding can distort high frequency pulse waveforms.
Even if it is wirewound, you can try it. Or you can go for a carbon
pot of up to 500 Ohms--I don't think the value will be critical in
this application.
In my "better" scenario, the pot is connected like a volume control
between the IIgs composite sync output and the monitor sync input.
A pot is a 3-terminal device--a resistor with a sliding tap. The
two outside terminals are the "ends" of the resistor, and the middle
terminal is the sliding tap.
You would connect the counterclockwise terminal (the "end" terminal
nearest the sliding tap when the pot is adjusted fully counterclockwise)
to ground (common to both the monitor and the IIgs). The other "end"
terminal (the clockwise terminal) would connect to the IIgs composite
sync output. The middle terminal (the sliding tap) would connect to
the monitor sync input.
Then you can adjust the sync input to the monitor from zero (fully
counterclockwise) to maximum (fully clockwise).
>>You may still find it worthwhile to adjust the vertical and horizontal
>>hold controls to the middle of their stable ranges. It seems that
>>this monitor's settings may have drifted a bit.
>
>
> The vertical hold was very difficult to adjust to get the image to
> stop rolling - i.e. there is a *very* small stable range for the
> vertical hold. But it was possible, as the images I posted previously
> confirm. I am guessing with a different resistor value this problem
> will rectify itself. This problem with vertical hold was only present
> using the RGB port however, when I hooked a DVD player up to it via
> the composite ports I had no such problem.
Interesting. I wonder what the sync output spec on the IIgs is?
Could it be TTL levels: 5v peak-to-peak? If that's the case, no
wonder the level needs to be reduced, since most monitors would
expect 1v or less peak-to-peak.
Hopefully, you will find a setting (guessing around 20%) that will
sync stably for both horizontal and vertical scan.
There is a possibility that the monitor expects the sync signal to
be opposite in polarity to what the IIgs outputs. If that is the
case, an inverter before the pot will straighten things out.
Needless to say, some definitive specs for the sync signal that
the IIgs produces and what the monitor expects would answer all
these questions.
>>>What would you guys recommend as the next course of action? All
>>>comments welcome.
>>
>>You're almost there!
>
>
> Great! I was hoping you'd say that. ;-)
If it "almost works" then you can't be far from having it work
perfectly.
Michael J. Mahon
I should have read ahead--I just suggested inversion, too. ;-)
Someone must have some specs on this monitor...?
BTW, since it syncs fine with a DVD player, I think the monitor is
fine.
Polymorph
Michael J. Mahon wrote:
>> Michael, as per all of the IIgs-->1084 FAQs suggest, I've only
>> connected the composite sync from the IIgs to the composite sync of
>> the 1084. Also note that in the 1084 the composite sync and horizontal
>> sync are tied together (the 1084S-D schematic I found confirms this).
>> I have left the vertical sync not connected as per the Apple II FAQ.
>
> I wasn't referring to the horizontal sync input, but to the horizontal
> sync (or "hold") adjustment on the monitor. This may be internal, or
> accessible only through use of an "alignment tool" through a hole in
> the back or bottom of the case. Ideally, it would be an external
> control like the vertical hold control.
OK, understood. After considerable snooping around on the circuit board,
I think I've found the horizontal hold control. It's internal, and not
very obvious to find - it's well away from all of the other internal
adjustment controls and is significantly smaller. Here is a picture:
http://apple2.sytes.net/DSC00022.jpg
As you can see, I will have to slide out the main circuit board to
adjust this - definitely not the easiest of adjustments, however the
circuit board is free to slide out, so it shouldn't be too hard.
<snip my ramblings>
> A 200 Ohm pot is perfect. Actually, I hope it's a carbon pot, not
> a wirewound pot. Low resistance pots may be wirewound, and the
> inductance of the winding can distort high frequency pulse waveforms.
How about one of these:
http://www.jaycar.com.au/productView.asp?ID=RT4350
OR
http://www.jaycar.com.au/productView.asp?ID=RT4304
> In my "better" scenario, the pot is connected like a volume control
> between the IIgs composite sync output and the monitor sync input.
> A pot is a 3-terminal device--a resistor with a sliding tap. The
> two outside terminals are the "ends" of the resistor, and the middle
> terminal is the sliding tap.
>
> You would connect the counterclockwise terminal (the "end" terminal
> nearest the sliding tap when the pot is adjusted fully counterclockwise)
> to ground (common to both the monitor and the IIgs). The other "end"
> terminal (the clockwise terminal) would connect to the IIgs composite
> sync output. The middle terminal (the sliding tap) would connect to
> the monitor sync input.
>
> Then you can adjust the sync input to the monitor from zero (fully
> counterclockwise) to maximum (fully clockwise).
Thanks Michael, that explanation cleared it up nicely.
>> The vertical hold was very difficult to adjust to get the image to
>> stop rolling - i.e. there is a *very* small stable range for the
>> vertical hold. But it was possible, as the images I posted previously
>> confirm. I am guessing with a different resistor value this problem
>> will rectify itself. This problem with vertical hold was only present
>> using the RGB port however, when I hooked a DVD player up to it via
>> the composite ports I had no such problem.
>
> Interesting. I wonder what the sync output spec on the IIgs is?
> Could it be TTL levels: 5v peak-to-peak? If that's the case, no
> wonder the level needs to be reduced, since most monitors would
> expect 1v or less peak-to-peak.
Well, I just tested the voltage on my IIgs' composite sync output, and
it measured ~3.87 Volts. With the 75 Ohm resistor wired up between
composite sync and ground (Jeff's suggestion), the voltage was pulled
down to ~0.56 Volts.
I dug up some info on the 1084 monitors here:
http://www.amiga-hardware.com/showhardware.cgi?HARDID=849
and here:
http://kmt.hku.nl/~pieter/HARD/MON/commodore1084.html
I'm not sure, but those sites seem to suggest that the input should be
0.7 P-P. What does P-P stand for? I assume 0.7 is the voltage level?
> Hopefully, you will find a setting (guessing around 20%) that will
> sync stably for both horizontal and vertical scan.
>
> There is a possibility that the monitor expects the sync signal to
> be opposite in polarity to what the IIgs outputs. If that is the
> case, an inverter before the pot will straighten things out.
>
> Needless to say, some definitive specs for the sync signal that
> the IIgs produces and what the monitor expects would answer all
> these questions.
As there are so many people successfully using 1084 monitors on a IIgs,
and nobody has mentioned the need for an inverter, I would guess that
this is not the case - but I could be wrong. I wouldn't think that even
if certain models were more tolerant of sync voltages, that they would
invert the signals for a particular model, as it would break
compatibility wouldn't it?
As always, thanks heaps for your time.
Cheers,
Mike
Michael J. Mahon
> To: Michael J. Mahon
> Michael J. Mahon wrote:
>
>>> Michael, as per all of the IIgs-->1084 FAQs suggest, I've only
>>> connected the composite sync from the IIgs to the composite sync of
>>> the 1084. Also note that in the 1084 the composite sync and horizontal
>>> sync are tied together (the 1084S-D schematic I found confirms this).
>>> I have left the vertical sync not connected as per the Apple II FAQ.
>>
>>
>> I wasn't referring to the horizontal sync input, but to the horizontal
>> sync (or "hold") adjustment on the monitor. This may be internal, or
>> accessible only through use of an "alignment tool" through a hole in
>> the back or bottom of the case. Ideally, it would be an external
>> control like the vertical hold control.
>
>
> OK, understood. After considerable snooping around on the circuit board,
> I think I've found the horizontal hold control. It's internal, and not
> very obvious to find - it's well away from all of the other internal
> adjustment controls and is significantly smaller. Here is a picture:
>
> http://apple2.sytes.net/DSC00022.jpg
That looks like it--and it's in the right neighborhood on the
PC board.
> As you can see, I will have to slide out the main circuit board to
> adjust this - definitely not the easiest of adjustments, however the
> circuit board is free to slide out, so it shouldn't be too hard.
Great. If you don't have a plastic adjustment tool, be careful. ;-)
> <snip my ramblings>
>
>> A 200 Ohm pot is perfect. Actually, I hope it's a carbon pot, not
>> a wirewound pot. Low resistance pots may be wirewound, and the
>> inductance of the winding can distort high frequency pulse waveforms.
>
>
> How about one of these:
> http://www.jaycar.com.au/productView.asp?ID=RT4350
>
> OR
>
> http://www.jaycar.com.au/productView.asp?ID=RT4304
Either one would work fine. (The first is a little better enclosed.)
Since most voltmeters will produce an average reading of a varying
waveform, and the open-circuit IIgs output is ~3.8v, that suggests
that the IIgs is outputting TTL level (5vpp) negative sync--meaning
that the sync pulses are negative-going from about ~+5v.
Adding the 75 Ohm resistor is not "terminating" the signal, but
simply attenuating it--in this case to about 0.7vpp (coincidentally
ideal for the monitor ;-).
> I dug up some info on the 1084 monitors here:
> http://www.amiga-hardware.com/showhardware.cgi?HARDID=849
>
> and here:
> http://kmt.hku.nl/~pieter/HARD/MON/commodore1084.html
>
> I'm not sure, but those sites seem to suggest that the input should be
> 0.7 P-P. What does P-P stand for? I assume 0.7 is the voltage level?
P-P stands for peak-to-peak.
You are currently supplying just about that level to the sync input.
Nothing states the expected polarity of the sync (or the video, for that
matter), so the conventional polarity is positive for video and negative
for sync. We can hope that that's true for this monitor. (Since others
have had good luck with it connected to a IIgs without using an
inverter, this seems a reasonable assumption.)
>> Hopefully, you will find a setting (guessing around 20%) that will
>> sync stably for both horizontal and vertical scan.
>>
>> There is a possibility that the monitor expects the sync signal to
>> be opposite in polarity to what the IIgs outputs. If that is the
>> case, an inverter before the pot will straighten things out.
>>
>> Needless to say, some definitive specs for the sync signal that
>> the IIgs produces and what the monitor expects would answer all
>> these questions.
>
>
> As there are so many people successfully using 1084 monitors on a IIgs,
> and nobody has mentioned the need for an inverter, I would guess that
> this is not the case - but I could be wrong. I wouldn't think that even
> if certain models were more tolerant of sync voltages, that they would
> invert the signals for a particular model, as it would break
> compatibility wouldn't it?
I come to the same conclusion.
I think that a little higher sync level than your fixed resistor
combined with an adjustment of the horizontal hold will put things
right.
> As always, thanks heaps for your time.
You're welcome--let's get it working for you!
Alex Freed
>
> I'm not sure, but those sites seem to suggest that the input should be
> 0.7 P-P. What does P-P stand for? I assume 0.7 is the voltage level?
Indeed it is 0.7 volts. P-P stands for "peak to peak" as opposed to say RMS.
>
> As there are so many people successfully using 1084 monitors on a IIgs,
> and nobody has mentioned the need for an inverter, I would guess that
> this is not the case - but I could be wrong.
I am one. No inverters needed, but the Amiga monitor I have appears to
have a strong internal pull-up. It's not the voltage that is a problem,
but rather the fact that it never gets low enough. My solution was a
51 ohm resistor to the ground. Works like a charm
-Alex.
Polymorph
Alex,
I'm just curious how you arrived at 51 Ohms. Was it through trial and
error, or some other means of deduction?
When you wired up the 51 Ohm resistor, I assume it was in the same
manner as I tried with a 75 Ohm resistor - i.e. the resistor between
the composite sync and ground?
Could you do me a favour and measure what the voltage is between
composite sync and ground? It could be that I haven't lowered my
composite sync signal quite enough? Maybe the sync level is 0.3V P-P.
I think this is what is listed for one of the other 1084 inputs.
Perhaps this is an omission from the specs of the RGB port?
Thanks for the help!
Cheers,
Mike
Alex Freed
> Alex,
>
> I'm just curious how you arrived at 51 Ohms. Was it through trial and
> error, or some other means of deduction?
"51" looks very precise - it's just a standard value I tried when 75
proved not to be low enough. I used a scope to see what the signal looks
like. I would not use a much lower value for fear of overloading the
GS's output driver, but 51 is safe.
>
> When you wired up the 51 Ohm resistor, I assume it was in the same
> manner as I tried with a 75 Ohm resistor - i.e. the resistor between
> the composite sync and ground?
Yes.
>
> Could you do me a favour and measure what the voltage is between
> composite sync and ground? It could be that I haven't lowered my
> composite sync signal quite enough? Maybe the sync level is 0.3V P-P.
> I think this is what is listed for one of the other 1084 inputs.
> Perhaps this is an omission from the specs of the RGB port?
I don't have this system connected at this time, sorry. However using
the 200 ohm pot as was suggested here should do the trick for you.
>
> Thanks for the help!
>
> Cheers,
> Mike
-Alex.
Polymorph
Alex Freed wrote:
> Polymorph wrote:
>> Alex,
>>
>> I'm just curious how you arrived at 51 Ohms. Was it through trial and
>> error, or some other means of deduction?
>
> "51" looks very precise - it's just a standard value I tried when 75
> proved not to be low enough. I used a scope to see what the signal looks
> like. I would not use a much lower value for fear of overloading the
> GS's output driver, but 51 is safe.
OK, so when I next go to the electronics store, I might pick up a 51 Ohm
resistor in addition to the 200 Ohm pot. As we're only talking a few
cents extra. Actually, it's rather embarrassing walking into an
electronics store and walking out with a 38 cent part. When I was
confronted with this problem the other day, I actually stood in the
store until I thought of something else I needed for a different project
just so that I didn't have to look the dealer in the eye when he said
"that'll be 38 cents please". ;-)
>
>>
>> When you wired up the 51 Ohm resistor, I assume it was in the same
>> manner as I tried with a 75 Ohm resistor - i.e. the resistor between
>> the composite sync and ground?
> Yes.
I thought that's what you meant.
>>
>> Could you do me a favour and measure what the voltage is between
>> composite sync and ground? It could be that I haven't lowered my
>> composite sync signal quite enough? Maybe the sync level is 0.3V P-P.
>> I think this is what is listed for one of the other 1084 inputs.
>> Perhaps this is an omission from the specs of the RGB port?
>
> I don't have this system connected at this time, sorry. However using
> the 200 ohm pot as was suggested here should do the trick for you.
No worries. Its good to hear of someone who experienced a similar
problem as myself using the 1084S with the IIgs. I wonder why most
people don't have a problem? Did later revisions of the 1084 line come
with greater tolerance to sync levels? It has me stumped how come some
1084 monitors require modification of the sync signal and others don't.
Thanks for letting me know your experiences in using the 1084 with the
IIgs, as it's almost made it a 100% sure thing for success (once I
twiddle the signal a little more).
Michael J. Mahon
> To: Alex Freed
> Alex Freed wrote:
>
>> Polymorph wrote:
>>
>>> Alex,
>>>
>>> I'm just curious how you arrived at 51 Ohms. Was it through trial and
>>> error, or some other means of deduction?
>>
>>
>> "51" looks very precise - it's just a standard value I tried when 75
>> proved not to be low enough. I used a scope to see what the signal
>> looks like. I would not use a much lower value for fear of overloading
>> the GS's output driver, but 51 is safe.
To elaborate:
Fixed value resistors come in certain values based on their tolerances.
For example, if a resistor is a 5% tolerance resistor, it wouldn't make
sense to make values less than 5% apart! The exact values chosen (for
the marked values--presumeably the center of the actual distribution of
values--are standardized:
10 11 12 13 15 16 18 20 22 24 27 30 33 36 39 43 47 51 56 62 68 75 82 91
and, of course, these values recur in every decade of values--the next
value is 100, then 110, etc.
Components with 10% tolerances are made in only half as many values:
10 12 15 18 22 27 33 39 47 56 68 82
So the marked value should not be interpreted as an exact value. ;-)
> OK, so when I next go to the electronics store, I might pick up a 51 Ohm
> resistor in addition to the 200 Ohm pot. As we're only talking a few
> cents extra. Actually, it's rather embarrassing walking into an
> electronics store and walking out with a 38 cent part. When I was
> confronted with this problem the other day, I actually stood in the
> store until I thought of something else I needed for a different project
> just so that I didn't have to look the dealer in the eye when he said
> "that'll be 38 cents please". ;-)
Never worry about this. If the store is concerned about their
transaction costs (which are almost certainly a few tens of cents)
then they should just give your the part! (And some will if they
know you. ;-)
The 200 Ohm pot will provide you with complete adjustment flexibility,
corresponding to *all* values of resistor, so you don't need another
fixed resistor for this.
>>> When you wired up the 51 Ohm resistor, I assume it was in the same
>>> manner as I tried with a 75 Ohm resistor - i.e. the resistor between
>>> the composite sync and ground?
>>
>> Yes.
>
>
> I thought that's what you meant.
>
>>>
>>> Could you do me a favour and measure what the voltage is between
>>> composite sync and ground? It could be that I haven't lowered my
>>> composite sync signal quite enough? Maybe the sync level is 0.3V P-P.
>>> I think this is what is listed for one of the other 1084 inputs.
>>> Perhaps this is an omission from the specs of the RGB port?
Specifying a video peak-to-peak level of 0.7v and a sync peak-to-peak
level of 0.3v corresponds to the standard composite video+sync level
of 1v (of which 0.7v is video going positive from black level and 0.3v
is sync going negative from black level).
It would not be unusual for the internals of the monitor to accept
composite sync at the same level and polarity at which it would be
found in a composite video signal.
>> I don't have this system connected at this time, sorry. However using
>> the 200 ohm pot as was suggested here should do the trick for you.
>>
> No worries. Its good to hear of someone who experienced a similar
> problem as myself using the 1084S with the IIgs. I wonder why most
> people don't have a problem? Did later revisions of the 1084 line come
> with greater tolerance to sync levels? It has me stumped how come some
> 1084 monitors require modification of the sync signal and others don't.
The sync level tolerance is strongly dependent on the input circuitry
of the monitor, and a very minor change would make it quite insensitive
to sync level. It would not be surprising if this were the case in
some of the monitors (which may have different manufacturers).
Polymorph
Michael J. Mahon wrote:
> transaction costs (which are almost certainly a few tens of cents)
> then they should just give your the part! (And some will if they
> know you. ;-)
OK, but it still feels kinda weird.
> The 200 Ohm pot will provide you with complete adjustment flexibility,
> corresponding to *all* values of resistor, so you don't need another
> fixed resistor for this.
OK, I'll stick with just the 200 Ohm pot then.
> Specifying a video peak-to-peak level of 0.7v and a sync peak-to-peak
> level of 0.3v corresponds to the standard composite video+sync level
> of 1v (of which 0.7v is video going positive from black level and 0.3v
> is sync going negative from black level).
>
> It would not be unusual for the internals of the monitor to accept
> composite sync at the same level and polarity at which it would be
> found in a composite video signal.
Right, that makes sense to me.
>>> I don't have this system connected at this time, sorry. However using
>>> the 200 ohm pot as was suggested here should do the trick for you.
> >>
>> No worries. Its good to hear of someone who experienced a similar
>> problem as myself using the 1084S with the IIgs. I wonder why most
>> people don't have a problem? Did later revisions of the 1084 line come
>> with greater tolerance to sync levels? It has me stumped how come some
>> 1084 monitors require modification of the sync signal and others don't.
>
> The sync level tolerance is strongly dependent on the input circuitry
> of the monitor, and a very minor change would make it quite insensitive
> to sync level. It would not be surprising if this were the case in
> some of the monitors (which may have different manufacturers).
I'm just surprised that I have had to drop the sync level to such a low
value though when others have not. I mean its gone from ~3.87V to
~0.56V, and it seems that it is still too high! This seems like a pretty
big difference. I'm still amazed that later revisions of the 1084 can
handle the IIgs' comp sync signal unmodified. It would be interesting to
know what they changed to allow for this to be possible (as I'm sure
they didn't have the IIgs in mind when making the 1084 monitors ;-).
Alex Freed
>
> I'm just surprised that I have had to drop the sync level to such a low
> value though when others have not. I mean its gone from ~3.87V to
> ~0.56V, and it seems that it is still too high! This seems like a pretty
> big difference. I'm still amazed that later revisions of the 1084 can
> handle the IIgs' comp sync signal unmodified. It would be interesting to
> know what they changed to allow for this to be possible (as I'm sure
> they didn't have the IIgs in mind when making the 1084 monitors ;-).
>
Again, it was not as much a matter of the LEVEL as a pull-up.
Doesn't matter how high the positive peak is as long as the LOW level
is low enough. For some reason the sync input (at least on my) Amiga
monitor has a strong pull-up. And the output of the GS seems to be
designed to SOURCE rather than SINK a signal. So the resistor is needed
not to attenuate the pulse, but to pull it's bottom low enough - below
the threshold of the circuit.
If nothing is connected to the GS's output you will measure (with a
scope, not a voltmeter!) a pulse going say from 0 to 3.5 volts.
The open input of the monitor will have 5 volts.
Take a resistor, say 75 ohms and connect between the sync INPUT and the
ground. You can measure, and this time you CAN use a voltmeter as the
level is constant, some voltage. Let's say it will be 1 volt. That may
be too high for the input circuit and not seen as a LOW level.
If you connect the GS to the monitor directly with no extra resistors,
you will see a pulse that may be exactly right P-P, but not going low
enough.
-Alex.
Polymorph
Alex Freed wrote:
I *think* I understood that. The 1084 monitor is pulling the sync levels
a little too high, so the resistor is used to pull them back to an
acceptable level. Is that correct?
Sorry, I'm only a pretend hardware guy - I leave the advanced stuff to
you guys (and if this isn't advanced - I rest my case!). :-)
thanks,
Michael J. Mahon
> To: Michael J. Mahon
> Michael J. Mahon wrote:
>
>> Never worry about this. If the store is concerned about their
>> transaction costs (which are almost certainly a few tens of cents)
>> then they should just give your the part! (And some will if they
>> know you. ;-)
>
>
> OK, but it still feels kinda weird.
And, of course, they wouldn't want to do a credit transaction. ;-)
Another consideration is *your* transaction costs, which can be
considerable if you have to make a special trip. But "spending
money to save money" is usually a dubious approach. ;-)
One thing you might consider, if you have any interest in doing
electronic repairs or experiments in the future, is getting a "kit"
of 200 or so 5% 1/4W resistors with a half-dozen or so of all the
common values. Such kits are usually about $5, so you are getting
a significant quantity discount, and you'll be prepared for just
about any small resistor needs. If you ever need another resistor,
the saving in time, trouble, and fuel is easily worth $5. ;-)
Adding an input buffer or Schmidt trigger would make the input quite
level-insensitive. This would add about $0.25 to the cost of the
monitor, but would broaden its specs enough that a single design could
be used in multiple applications without adjustements--a potential win.
Michael J. Mahon
Using a strong pull-up on a sync input is quite unusual--more common
for a "dedicated" monitor than a general-purpose monitor.
Since Commodore was nothing if not concerned with cost-reduction,
they may have initially adopted general-purpose monitors with only
minor customization from the OEMs design.
It was apparently common for dedicated monitors to use TTL levels for
H and V drive signals, or even for composite sync.
But I'd expect that a dedicated design would have to be produced in
large quantities before the non-recurring costs of customization were
recouped. The confidence that this will be a win usually comes later
in a product cycle. ;-)
Michael J. Mahon
BTW, a general-purpose design would usually AC-couple the sync signal,
to make operation independent of DC levels.
Alex Freed
>
> BTW, a general-purpose design would usually AC-couple the sync signal,
> to make operation independent of DC levels.
>
Sure, but this is a brand "A" monitor for a particular brand "A"
computer. If it does not interoperate with a competitor's product the
marketing department may see it as a "feature".
BTW a friend had an old computer and no monitor for it. On my advice he
bought the same 1084 on e-bay for a few bucks. Now his computer had the
opposite polarity of the sync signal, but since the 1084's input was DC
coupled, I was able to put a transistor into the connector shell as an
inverter with no power supply - 1084 provided the power.
-Alex.
Polymorph
Good and bad news...
OK, I have wired up the 200 Ohm pot and it does successfully fix the
sync problem. The monitor produces a nice crisp image. :-) I thought
it was a matter of case closed. My daughter played with the computer for
quite a while before I noticed different troubles.
Unfortunately, after the monitor is turned on for about 30-40 minutes,
it starts making a noise and the screen shimmies a bit (horizontally).
It seems to be related to the brightness/contrast somehow. Lowering the
brightness and/or contrast makes the problem appear worse, setting high
contrast/brightness make the problem go away.
All testing from this point was done with the monitor standalone - i.e.
there was no input source. I simply left the monitor on until the noise
recurred and attempted the following.
I opened the case again and tried the horizontal hold adjustment, and it
changed the pitch of the noise being produced, but that is all.
Originally I thought it was probably the main 150uF 400V capacitor
making the noise (by ear it sounded in the vicinity), so I replaced it
with a known good one that I had. It made no difference.
By moving a microphone *carefully* near the components, I was able to
determine where the noise was coming from (without the use of the
microphone it was impossible to tell where the sound was coming from). I
narrowed it down to two components - L301 or L202. I copied the
schematic for the 1084S-D onto my website:
http://apple2.sytes.net/1084S-D.gif
I took a couple of photo's of the suspected noise makers:
http://apple2.sytes.net/1084a.jpg
http://apple2.sytes.net/1084b.jpg
Now, for my questions:
1) is it likely that one of the components making the noise is faulty,
or one of the surrounding components? (e.g. a capacitor)
2) if L301 or L202 faulty, are those parts easy to find replacements for?
3) is there something else that is likely causing the noise? Bear in
mind that I'm fairly confident that the location I have indicated is
where the noise is coming from (the record levels peaked out around here).
I swear by the end of all this I'll be able to open my own monitor
repair shop. :-)
Oh yeah, and why can't I get a monitor that just works?!?
Thanks,
fer...@gmx.de
this> wrote:
> To: Polymorph
> Good and bad news...
>
> OK, I have wired up the 200 Ohm pot and it does successfully fix the
> sync problem. The monitor produces a nice crisp image. :-) I thought
> it was a matter of case closed. My daughter played with the computer for
> quite a while before I noticed different troubles.
>
> Unfortunately, after the monitor is turned on for about 30-40 minutes,
> it starts making a noise and the screen shimmies a bit (horizontally).
> It seems to be related to the brightness/contrast somehow. Lowering the
> brightness and/or contrast makes the problem appear worse, setting high
> contrast/brightness make the problem go away.
>
> All testing from this point was done with the monitor standalone - i.e.
> there was no input source. I simply left the monitor on until the noise
> recurred and attempted the following.
>
> I opened the case again and tried the horizontal hold adjustment, and it
> changed the pitch of the noise being produced, but that is all.
>
> Originally I thought it was probably the main 150uF 400V capacitor
> making the noise (by ear it sounded in the vicinity), so I replaced it
> with a known good one that I had. It made no difference.
>
> By moving a microphone *carefully* near the components, I was able to
> determine where the noise was coming from (without the use of the
> microphone it was impossible to tell where the sound was coming from). I
> narrowed it down to two components - L301 or L202. I copied the
> schematic for the 1084S-D onto my website:
>
> http://apple2.sytes.net/1084S-D.gif
>
> I took a couple of photo's of the suspected noise makers:
>
>
> Now, for my questions:
>
> 1) is it likely that one of the components making the noise is faulty,
> or one of the surrounding components? (e.g. a capacitor)
> 2) if L301 or L202 faulty, are those parts easy to find replacements for?
> 3) is there something else that is likely causing the noise? Bear in
> mind that I'm fairly confident that the location I have indicated is
> where the noise is coming from (the record levels peaked out around here).
>
circuit.
The noise and horizontal jitter problem is caused by the horizontal
deflections failure to produced equally long lines. This causes the
current through all parts in the horizontal output stage to vary
making them vibrate and generate some noise. They are not at fault!
If you increase the load to the horizontal output stage by increasing
the picture's brightness (remember that the HOS also generates the
high voltage for the picture tube; in this set all voltages for the
video section are generated this way - thats what T202(flyback
transformer/FBT) is for.), you make it run more stable.
Really fixing this is difficult; it can be caused by
- bad(usually low) sync input (but not here, because it also happens w/
o sync)
- the oscillator circuit (I201)
- the horizontal driver, HOT(horizontal output transistor, Q202)
- the circuitry around the yoke
- low or high line voltage or power supply fault (suspect here: most
likely C222, but also C117, C116)
- poor design
- bad luck (i.e. combination of poor design, low/high line voltage,
and tolerances of exactly this model)
Because bad luck is the most likely cause there is usually nothing to
replace, but there are workarounds:
The problem usually disappears if the parameters of the HOS are varied
slightly. this includes:
- Horizontal phase R203 (moves the picture horizontally)
- Horizontal hold (but you've already tried it)
- Horizontal width L201 (you should be able to CAREFULLY screw in/out
its core - try it with power off before!)
- Horizontal drive level (modify R210, R211 or R212 slightly -
dangerous w/o oscilloscope)
- Horizontal feedback level (modify R255 or R247, e.g. use 33K or
39K) - you won't blow anything with this mod.
- Power supply voltage (my favorite - but there is no pot for it in
this set)
- live with it (many modern VGA monitors show this problem in out of
the box in text mode (mostly black screen - got it?) - especially
Samsungs.)
> I swear by the end of all this I'll be able to open my own monitor
> repair shop. :-)
You won't be able to make a living with it. there are not enough CRT
monitors out there any more...
>
> Oh yeah, and why can't I get a monitor that just works?!?
I asked that myself a couple of times, but now I know: It's just
boring.
-----
Ferdinand Meyer-Hermann
Polymorph
ferdimh wrote:
<snip>
>> Originally I thought it was probably the main 150uF 400V capacitor
>> making the noise (by ear it sounded in the vicinity), so I replaced it
>> with a known good one that I had. It made no difference.
> Where is it? I didn't find it on the schematic...
The capacitor I was referring to is at C109 which is listed as a 200uF
200V capacitor on the schematic, however, because I am in Australia we
are using 240V power, so I guess the need for a higher voltage capacitor?
<snip>
> This is nearly always a problem in the horizontal deflection or driver
> circuit.
> The noise and horizontal jitter problem is caused by the horizontal
> deflections failure to produced equally long lines. This causes the
> current through all parts in the horizontal output stage to vary
> making them vibrate and generate some noise. They are not at fault!
> If you increase the load to the horizontal output stage by increasing
> the picture's brightness (remember that the HOS also generates the
> high voltage for the picture tube; in this set all voltages for the
> video section are generated this way - thats what T202(flyback
> transformer/FBT) is for.), you make it run more stable.
> Really fixing this is difficult; it can be caused by
> - bad(usually low) sync input (but not here, because it also happens w/
> o sync)
> - the oscillator circuit (I201)
> - the horizontal driver, HOT(horizontal output transistor, Q202)
> - the circuitry around the yoke
> - low or high line voltage or power supply fault (suspect here: most
> likely C222, but also C117, C116)
> - poor design
> - bad luck (i.e. combination of poor design, low/high line voltage,
> and tolerances of exactly this model)
OK, I hope its not bad luck, because in its current state its borderline
usable. If I choose to have a black background and black border via the
IIgs control panel, the image is unstable and I get the noise no matter
how far I turn up the brightness/contrast. I haven't tried replacing the
capacitors you suggested as yet, but I will endeavour give that a try
over the weekend.
> Because bad luck is the most likely cause there is usually nothing to
> replace, but there are workarounds:
> The problem usually disappears if the parameters of the HOS are varied
> slightly. this includes:
> - Horizontal phase R203 (moves the picture horizontally)
I had already tried adjusting R203 without success.
> - Horizontal hold (but you've already tried it)
> - Horizontal width L201 (you should be able to CAREFULLY screw in/out
> its core - try it with power off before!)
I tried adjusting L201, but it didn't help.
> - Horizontal drive level (modify R210, R211 or R212 slightly -
> dangerous w/o oscilloscope)
I haven't tried the above - I don't own or have access to an oscilloscope.
> - Horizontal feedback level (modify R255 or R247, e.g. use 33K or
> 39K) - you won't blow anything with this mod.
I haven't tried the above as yet.
> - Power supply voltage (my favorite - but there is no pot for it in
> this set)
> - live with it (many modern VGA monitors show this problem in out of
> the box in text mode (mostly black screen - got it?) - especially
> Samsungs.)
As I mentioned above, it would be hard to live with as it is now. The
combination of the noise plus the unstable image is too much to live
with IMHO.
>> I swear by the end of all this I'll be able to open my own monitor
>> repair shop. :-)
> You won't be able to make a living with it. there are not enough CRT
> monitors out there any more...
I was only joking. Once I get this thing sorted out, I don't want to see
the insides of another monitor for a long time.
>> Oh yeah, and why can't I get a monitor that just works?!?
> I asked that myself a couple of times, but now I know: It's just
> boring.
At this point, I'd kill for boring. ;-)
Thanks for your help,
fer...@gmx.de
bad luck...
You could try replacing C222 or just bridging with your 150µF/400V
cap. At least in theory there cold be a fault elsewhere but this would
be VERY difficult to find, even with an oscilloscope. Using could
spray to cool the parts related to the horizontal output stage one at
a time can help to locate the fault.
BTW does the problem disappear if the power is turned off for a short
time (i.e. 1 minute or so)?
Well I'd be interested in fixing these monitors because they have
interesting defects, but this is not an option.
----
Ferdinand
Polymorph
> If the things you tried didn't help at all, then it doesn't seem to be
> bad luck...
> You could try replacing C222 or just bridging with your 150µF/400V
> cap. At least in theory there cold be a fault elsewhere but this would
> be VERY difficult to find, even with an oscilloscope. Using could
> spray to cool the parts related to the horizontal output stage one at
> a time can help to locate the fault.
I'll give your suggestions a try. I've used up all of my cooling
spray, so I'll need to get some more prior to trying this.
> BTW does the problem disappear if the power is turned off for a short
> time (i.e. 1 minute or so)?
I believe it does go away when turned off for a minute or two, but
returns quicker than if the unit was cold. It does appear to be heat
related.
> Well I'd be interested in fixing these monitors because they have
> interesting defects, but this is not an option.
I'm interested in fixing *this* monitor as I bought it for my
daughter, but in future I would prefer to have a working monitor
straight away. With 2 young kids and 200+ driving per day, I don't
have much spare time up my sleeve to be worrying about these things.
Mind you, it has been educational and I am sure I have benefited from
the experience imparted from you (Ferdinand) and MJM.
Cheers,
Mike
Michael J. Mahon
> On Feb 20, 4:01 am, ferd...@gmx.de wrote:
>
>>If the things you tried didn't help at all, then it doesn't seem to be
>>bad luck...
>>cap. At least in theory there cold be a fault elsewhere but this would
>>be VERY difficult to find, even with an oscilloscope. Using could
>>spray to cool the parts related to the horizontal output stage one at
>>a time can help to locate the fault.
>
>
> I'll give your suggestions a try. I've used up all of my cooling
> spray, so I'll need to get some more prior to trying this.
>
>
>>BTW does the problem disappear if the power is turned off for a short
>>time (i.e. 1 minute or so)?
>
>
> I believe it does go away when turned off for a minute or two, but
> returns quicker than if the unit was cold. It does appear to be heat
> related.
(Sorry for not chiming in earlier--I was travelling. ;-)
I think cooling spray is the correct route to locating the problem.
(Do avoid spraying it near the HV components, though. Components
outside the "cage" are fine.)
The "singing" component is almost certainly just a symptom of
the problem, not its cause, which, as Ferdinand has pointed out,
is instability in the horizontal output stage.
Almost any component can be temperature sensitive, but capacitors
and resistors are high on the list.
From your description of the problem, it sounds like it will be
easy to locate with a 10-20 degree temperature drop.
>>Well I'd be interested in fixing these monitors because they have
>>interesting defects, but this is not an option.
>
>
> I'm interested in fixing *this* monitor as I bought it for my
> daughter, but in future I would prefer to have a working monitor
> straight away. With 2 young kids and 200+ driving per day, I don't
> have much spare time up my sleeve to be worrying about these things.
> Mind you, it has been educational and I am sure I have benefited from
> the experience imparted from you (Ferdinand) and MJM.
Most people don't relish repair work, but it is inevitably educational,
and adds to your confidence that you can fix other things. ;-)
Polymorph
> Polymorph wrote:
> > On Feb 20, 4:01 am, ferd...@gmx.de wrote:
>
> >>If the things you tried didn't help at all, then it doesn't seem to be
> >>bad luck...
> >>cap. At least in theory there cold be a fault elsewhere but this would
> >>be VERY difficult to find, even with an oscilloscope. Using could
> >>spray to cool the parts related to the horizontal output stage one at
> >>a time can help to locate the fault.
>
> > I'll give your suggestions a try. I've used up all of my cooling
> > spray, so I'll need to get some more prior to trying this.
>
> >>time (i.e. 1 minute or so)?
>
> > I believe it does go away when turned off for a minute or two, but
> > returns quicker than if the unit was cold. It does appear to be heat
> > related.
>
> (Sorry for not chiming in earlier--I was travelling. ;-)
>
> I think cooling spray is the correct route to locating theproblem.
> (Do avoid spraying it near the HV components, though. Components
> outside the "cage" are fine.)
>
> The "singing" component is almost certainly just a symptom of
> is instability in the horizontal output stage.
>
> Almost any component can be temperature sensitive, but capacitors
> and resistors are high on the list.
>
> easy to locate with a 10-20 degree temperature drop.
>
> >>Well I'd be interested in fixing these monitors because they have
> >>interesting defects, but this is not an option.
>
> > I'm interested in fixing *this* monitor as I bought it for my
> > daughter, but in future I would prefer to have a working monitor
> > straight away. With 2 young kids and 200+ driving per day, I don't
> > have much spare time up my sleeve to be worrying about these things.
> > Mind you, it has been educational and I am sure I have benefited from
> > the experience imparted from you (Ferdinand) and MJM.
>
> Most people don't relish repair work, but it is inevitably educational,
> and adds to your confidence that you can fix other things. ;-)
>
> -michael
>
> NadaPong: Network game demo for Apple II computers!
> Home page: http://members.aol.com/MJMahon/
>
> "The wastebasket is our most important design
>
> - Show quoted text -
Well, after spending some time last night with a new bottle of cooling
spray, I think I can confirm that Ferdinand was on the right track
when he mentioned the capacitors C116 and C117. Applying cooling spray
to these caps made the problem disappear temporarily. As these
capacitors are right next to each other, I couldn't tell for certain
which one was at fault; or if both of them were. I'll try and source a
replacement capacitor from my old (now dead) Philips monitor -
hopefully I can find a 100uF cap of high enough voltage (160V+) to use
as a replacement. I do have a 100uF 400V capacitor, but due to its
size and the confined space around C116 and C117, I don't think it
will fit.
Anyway, I thought I'd give a progress update. I'll let you know how I
get on when I start replacing capacitors.
Hopefully once this is done, my monitor will be 100% working. :-)
Cheers,
Mike
Steven Hirsch
> Well, after spending some time last night with a new bottle of cooling
> spray, I think I can confirm that Ferdinand was on the right track
> when he mentioned the capacitors C116 and C117. Applying cooling spray
> to these caps made the problem disappear temporarily. As these
> capacitors are right next to each other, I couldn't tell for certain
> which one was at fault; or if both of them were. I'll try and source a
> replacement capacitor from my old (now dead) Philips monitor -
> hopefully I can find a 100uF cap of high enough voltage (160V+) to use
> as a replacement. I do have a 100uF 400V capacitor, but due to its
> size and the confined space around C116 and C117, I don't think it
> will fit.
Don't overlook the possibility of a bad solder joint! Sometimes one can get
fooled when playing with freeze spray, particularly if there's a delayed
reaction as the temperature change works its way through the PC board.
Polymorph
<snip>
>
> Don't overlook the possibility of a bad solder joint! Sometimes one can get
> fooled when playing with freeze spray, particularly if there's a delayed
> reaction as the temperature change works its way through the PC board.
Good idea! Thanks Steven. I'll try re-soldering both capacitors and
see if the situation improves. I hadn't thought of that. I take it
that under higher operating temps, a bad solder joint can open up?
Cheers,
Mike
Michael J. Mahon
A bad solder joint (or a hairline crack in a copper trace) can open
under *any* change in condition! Pressing with a plastic tool to flex
the board gently while observing the circuit's operation is a good way
to localize such mechanical defects.
BTW, if you use a narrow plastic tube with cooling spray, you can
direct it much more selectively.
Another technique is to clamp an alligator clip onto a lead of
the suspect component, close to the component, then spray the clip
in such a way that the overspray doesn't hit anything relevant.
Heat conduction will then lower the temperature of that component
quite selectively.