Astron RS-12A Repair Help
Woods Wannamaker
It's been on the shelf since but I am considering repairing it.
Symptons are: when power is applied, the power light comes on and I
hear the hum of the transformer, but there is no dc on the terminals.
Should I start by replacing the two transitors (2N3771)?
I would appreciate help/advice from anyone on how to trouble shoot
this.
Thanks in advance,
Woods
Chuck/KE4ETH
Hope this is of help.
--
73,
Chuck
KE4ETH
USA-NA
Remove the obvious from Email.
"Woods Wannamaker" <e_2t...@yahoo.com> wrote in message
news:88981065.0301...@posting.google.com...
Stephen C. Robbins
"Chuck/KE4ETH" <chuck...@hotmailNOSPAMORAMA.com> wrote in message
news:b_2W9.38463$Jm2....@news.bellsouth.net...Excellent resource! Thanks Chuck.
You probably want to disconnect the output leads of the transformer and check the transformer. If it
is good AC output, then it is probably economical to repair.
Steve
Roger Leone
Power supplies like yours are pretty easy to repair, but the best way is not
to randomly replace parts. There are many possible problems and you need to
approach the troubleshooting in an organized way, eliminating what is
working and moving on to what isn't. You will need a volt/ohmmeter for this
work.
Here is a link to a schematic that works:
http://www.repeater-builder.com/rbtip/rs12a.html
As a previous poster suggested, check to see if you have AC coming out of
the transformer. If you don't, check the fuse and switch on the primary
side. If they are good and you still have no AC out of the transformer, and
all the wiring seems OK and you have 117 volts AC going in the primary, then
the transformer may have an open secondary winding. This is unlikely, but
you should check to be sure. If the transformer is bad, you need to decide
how badly you want to repair the supply, as that is the most expensive part.
If you have AC coming out of the transformer, then check to see if you have
DC on the filter cap(s). It should be in the 16 - 22 volt range on the
17,000 mfd cap and even higher on the 1000 mfd cap. If you don't find these
two voltages, you probably have blown diodes. Check all 4 of them with an
ohmeter..two are separate and two are molded in a single module. If bad
they will either read as open or shorted with the ohmmeter leads on either
way. If good, they will conduct one way but not the other. They are
relatively inexpensive to replace if they are bad.
If the diodes are good and you have DC on your filter caps, then your
regulator chip, driver or output transistor(s) are bad. You can check the
transistors with your ohmmeter, like the diodes, looking for opens or
shorts. It is a little more complicated and can be confusing because of the
extra terminals. The chip isn't as easy to test so if you have satisfied
yourself that tall the other parts are OK, then try subsitituing a chip.
The 723 regulator chip is very common and you should have no trouble finding
one to use.
If I had to make a guess, I would bet the regulator chip is bad. It is the
most fragile part and is easy to destroy (don't ask me how I know this).
Good luck,
Roger K6XQ
Frank Dinger
Suggest you take it step by step.
First apply power (presumably 117 V) and check AC output of secondary (Low
Voltage) transformer winding .
With the winding output ( if OK ) probably between 18 and 24 V, load the
winding with 2 car head light bulbs in series and check voltage on this load
. If voltage is hardly any lower than without load , then transformer is
OK.
Now check output rectifier module or discrete diodes DC voltage . If between
20 - 30 V these are OK
Now you can start checking components on the regulator circuit board ie
transistors , perhaps an opamp or voltage control IC or perhaps a separate
zener diode and the passive components .
Does the unit have a 'crowbar' over voltage trip circuit with a thyristor
and an associated fuse ? If there is a DC fuse ,is it OK or blown ?
Following a lightning strike ,if there is no visible damage ,semiconductors
(ICs) are the most likely victims.
Good Luck
Frank gm0csz...@ntlworld.com
Jim Pennell
was going high enough to trip the built in crowbar circuit.
And, as another poster suggested, it did turn out the be the LM723
voltage regulator IC.
For my troubleshooting, I removed the wire going the the SCR and that
disabled the crowbar. After doing that, the rest was easy to fix.
Jim Pennell
N6BIU
K9SQG
components should be replaced if they are not too numerous/expensive. I used
to service TV sets and it seems that the lightening strike cases always had
multiple problems. You'd fix one problem, and it would be back a few weeks
later with another. You'd fix that, and then back again. It became
impractical to continue the repairs.
Jim Shorney
>
> My RS-12A power supply died after a lightening strike in Summer 2001.
> It's been on the shelf since but I am considering repairing it.
I have one of these I picked up at a hamfest for $15. Same symptoms. I
went to RadShack and got a new 723 (less than $1) and popped it in, no
problems since. Replace the 723 first, they are cheap and common, and a
more cost-effective first step than actual troubleshooting.
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Bill Higdon
had lightning strike the main AC feed into the building. Instead of
leaving the X-ray system as dead and calling their insurance company.
They had the X-ray system fixed, the insurance company would have
replaced the X-ray system if they hadn't had it repaired. But as they
had it repaired, the insurance company would only pay for the inital
repair. After about 3years, and many service calls they finally sprung
for a new system.
Bill Higdon
W9GB
Here is a popular article on repairing the Astrons that took a lightning hit
and
hombrewing your own - good theory on how it all works with the 723 regulator
IC
David Metz, WA0AUQ
Regulated Power Supply construction
(or what's Inside your Astron)
http://www.seits.org/features/pwrsup.htm
Schematic for this design
http://www.seits.org/features/pwrsup.gif
This and the Astron schematic and you are off to fixing your unit.
BTW, I have an RS-12 on the bench right now --
another cheap acquisition - 723 first item replaced !
w9gb
"Woods Wannamaker" <e_2t...@yahoo.com> wrote in message
news:88981065.0301...@posting.google.com...
Lou
"brown out" due to lights flickering from either a storm or power line
problem. Nothing else, not even my "unprotected" computer (which was on at
the moment) took a hit. In both cases, it was the Bridge Rectifiers at
fault.
--
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"W9GB" <w9...@arrl.net> wrote in message
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Frank Dinger
"Lou" <te...@dp.net> wrote in message news:b0cg1j$1u01$1...@news.dp.net...
> I had (2) 20 amp Astrons go south on me in a week. Both were the result of
a
> "brown out" due to lights flickering from either a storm or power line
> problem. Nothing else, not even my "unprotected" computer (which was on at
> the moment) took a hit. In both cases, it was the Bridge Rectifiers at
> fault.
Since the discussion is on Astron Power Supply Units , may I bring up
another subject regarding these units
I have a RS-50A unit , 13.8 V -50Amperes max ., Astron serial nr 8804024.
Although provided with a Yaesu sticker and bought in the UK ,the unit is
made in the USA ,hence it is highly likely that the transformer is
designed for 234V- 60Hz. Here in Europe (incl.Scotland) the AC freq is 50
Hz. and we have fused power lead plugs .
For the Astron unit I fitted a 13 Amp fuse .
I have 2 problems with the unit :
1) When switched on after having been idle for some time the mains circuit
breaker trips due to the high inrush current ,but the 13 Amperes fuse
survives and so does the 10 Amperes fuse ,fitted on the unit.
Cure : I'll fit a 50 Ohms -50 Watts resistor with integral heatsink in
series with the primary transformer winding. As soon as the DC output
voltage is present (with a few seconds time delay) the contact of a DC coil
relay shorts the resistor providing the transformer with the full (nominal)
230 V - 50 Hz AC supply .
2) When switched on the transformer being located close to the metal cabinet
acts as a loud 'hum producing transducer'
I am sure this problem would not exist had the the transformer be a torodial
type.
I now intend putting the PSU in a wooden enclosure ,but before doing that I
would appreciate any feedback regarding the use of the RS-50A in the USA
or other countries with a 60 Hz power supply system.
TIA for any response
Frank gm0csz...@ntlworld.com
Ralph Mowery
"> would appreciate any feedback regarding the use of the RS-50A in the
USA
> or other countries with a 60 Hz power supply system.
>
> TIA for any response
>
> Frank gm0csz...@ntlworld.com
The power supply transformer will be slightly more efficient at 60 HZ and
the filter capacitors will eliminate somewhat more ripple in the supply.
Overall it should work beter.
Woods Wannamaker
the transformer is ~120V AC. Voltage across the two wires coming from
the secondary (blue and yellow) into the bridge rectifier (BR) is ~38V
AC. Voltage across the other side of the BR (yellow and red wires) is
~18V AC. Voltage feeding onto the cirucit board from the BR is 18V. I
actually get a reading both AC and DC there. The 16000 and 1000 mfd
filter caps have 25 and 32 V DC, respectively. Voltage on the
transistors is ~14V DC.
D1 and D2 conduct in one direction but show reflectance in the other.
D3 and D4 conduct in both directions (hmmm). Voltage across the D1 and
D2 is 32V DC. Voltage across D3 and D4 is nil (even on the most
sensitive scale). Does this identify the diodes D3 and D4 as
defective? I suppose the LM723 chip could also be defective. How do I
determine the correct replacements for D3 and D4, should these be the
problem- from the schematic?
Thanks for all the helpful posts and email responses.
Woods
Brian Griffey
at that point...
--
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Brian Griffey
See the SkyWave Linear Amplifier at
http://home.att.net/~briangriffey/Index.html
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"Woods Wannamaker" <e_2t...@yahoo.com> wrote in message
news:88981065.0301...@posting.google.com...
john graesser
"Brian Griffey" <briang...@worldnet.att.net> wrote in message
news:3HIW9.3488$zF6.2...@bgtnsc04-news.ops.worldnet.att.net...
> How much AC are you getting after the bridge? You shouldn't be getting
much
> at that point...
Since the output of the bridge is pulsed DC it will have both DC and AC
components.
If the capacitors are bad they will never charge up and even out the voltage
swings from the bridge.
It will appear to be AC at roughly half the input voltage on a cheap meter.
Is there an Oscope available to help check out the equipment? Or is the
repair being done with just a vom?
thanks, John.
KC5DWD
Brian Griffey
I hope not...
--
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Brian Griffey
See the SkyWave Linear Amplifier at
http://home.att.net/~briangriffey/Index.html
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
"john graesser" <grae...@tca.net> wrote in message
news:v2n3vg2...@corp.supernews.com...
rsa...@gmail.com
Ross AD6OE
Ralph Mowery
rsa...@gmail.com says...
>
> I am having similar problems with my RS12 supply. I think I shorted a pass transistor case to ground and output went to zero. Checked the transistors and they seem good. Replaced the 723 chip and output returned to 13.8v, but after cycling the supply a few times it fell to 8v. Any ideas? I'm new to repairing but am learning a
lot. Thanks for any help.
>
> Ross AD6OE
>
>
astrons will often trip the over voltage protection if you do no twait
about 3 to 5 seconds to turn it back on after turning it off.
They also have a problem with the transistor sockets. The small pins of
te transistors often fail to make good contact with the sockets.
Allodoxaphobia
> On Saturday, January 18, 2003 at 12:10:59 AM UTC-8, Roger Leone wrote:
>
> I am having similar problems with my RS12 supply.
of replying to a FIFTEEN YEAR-OLD THREAD!
Michael Black
to make it easier for others to find.
What's forgotten is that the only way someone finds these old threads is
by searches (I can't believe they scroll back through 16 years of
messages), and if they can find a message from 2003, the same sort of
search would find a new thread started today.
Michael
Rob
Groups" interface to usenet news. It archives news forever, then allows
people to search it and send replies, without any clear indication that
they are replying to very old news. There should be an extra warning
when replying to an old thread, or it should be disallowed entirely.
Even those that ask the questions are unlikely to ever come back to read
the replies. They were just searching the internet, found the article
on Google Groups that they do not regularly visit otherwise, ask a
question and move on in their search. It is unlikely that they can find
back the same Google Groups site 3 days later to read a reply.
So it is best to just ignore those replies to old threads from people
with @gmail.com. I have even setup a killfilter so I don't see them.
(unless others again reply to them)
Fred McKenzie
> Even those that ask the questions are unlikely to ever come back to read
> the replies. They were just searching the internet, found the article
> on Google Groups that they do not regularly visit otherwise, ask a
> question and move on in their search. It is unlikely that they can find
> back the same Google Groups site 3 days later to read a reply.
have an idea that might help, I'll provide it.
But you are correct. There is seldom any further response. And if I
research the thread, I often find it is an old thread I previously
replied to, and provided the same suggestion.
I suspect they expect replies by E-Mail, so there is no need to come
back!
Fred
Bob Wilson
But as I get older it can be nice to see, when I find I am saying the
same thing I did years ago!
Bob W, WA9D
rsa...@gmail.com
Ross AD6OE
Jim
shortage of things to be outraged about ATM, so people jump on whatever
they can get.
Fred McKenzie
> I am having similar problems with my RS12 supply. I think I shorted a pass
> transistor case to ground and output went to zero. Checked the transistors
> and they seem good. Replaced the 723 chip and output returned to 13.8v, but
> after cycling the supply a few times it fell to 8v. Any ideas?
For a shorted pass transistor case-to-ground, I would expect a problem
with rectifier diodes. It is ALSO possible you now have another bad
723. If the high current rectifiers are open, you might initially
measure 13.8 volts with no load. With any load, the 723 might be
stressed.
The RS-12A uses two sets of rectifiers. One is for the low power
regulator circuit, the other has a higher current rating and feeds the
pass transistors. The diagram I have uses a single MDA2501 for the high
current rectifiers. (It is dated 6/20/88.)
Fred
K4DII
G. Beat
by Repeater Builders Technical Information Page (RBTIP)
* Compiled from a number of different sources *
http://www.repeater-builder.com/astron/astron-intro-stuff.html
Schematics and Service Information on Astron™ Power Supplies
by Repeater Builders Technical Information Page (RBTIP)
http://www.repeater-builder.com/astron/astron-index.html
Regulated Linear Power Supply Construction
What's inside your Astron®?
by David Metz, WA0AUQ
http://www.repeater-builder.com/astron/pdf/seits-astron-article.pdf
Power Supply Analysis using Astron DC Supply
Hands On Radio, QST magazine
by H. Ward Silver, N0AX
http://www.repeater-builder.com/astron/pdf/power-supply-analysis.pdf
===
The Illuminated Rocker Switch, used as Power Switch on Astron RA and RM-series DC power supplies,
The Neon Bulb within the switch series has a lifetime of ~20 years, comparable to LED devices.
Astron uses the appliance standard-sized (.480" x 1.072"; 12.19mm x 27.23mm) switch cutout.
Illuminated (neon) Rocker switch, LRA211-RS-B/125N (translucent red).
http://www.carlingtech.com/sites/default/files/documents/LRA-Series_Details_&_COS_0.pdf
This switch size is widely available from electrical, electronic, appliance part distributors
(Mouser, DigiKey, Newark, Allied, Future, NTE Electronics, GC Electronics/Waldom) and
manufactured by: C&K, Carling, Cherry, Alcoswitch, and numerous Eastern Asia shops.
I have seen prices for this illuminated Carling LRA211 Rocker Switch from $2.00 to $15.00 each.
BE a SMART Shopper.
The higher priced rocker switches are usually found at electrical or appliance distributors and
"convenient” retail hardware locations (example: Jandorf brand name).
NTE Electronics : Illuminated Rocker Switches
PART Number: 54-065, this is the Carling LRA211-RS-B/125N (translucent red).
https://www.nteinc.com/switches/pdf/rocker-illum.pdf
GC Electronics product (35-3740) is a good compromise of price and convenience.
http://www.gcelectronics.com/order/Catalog_PDF/2007 Catalog 120407 294.pdf
The GC part (35-3740) is the Carling “Curvette” LRA series, specifically LRA211-CR-B/125N (ruby red)
LRA211: 125V Neon Lamp; 16A 125VAC; .250 QC Tabs; OFF-NONE-ON (SPST); Red Clear, Black bezel.
G. Beat
Written by Eli, Vetco Electronics
by Thursday, May 04, 2017.
Ask any field or bench technician what their most-used piece of test equipment is and
they will probably say a VOM (VoltOhm Meter) or DMM (Digital MultiMeter).
These versitiale devices can be used to test and diagnose a wide range of circuits and components.
In a pinch, a DMM can even substitute for expensive, specialized test equipment.
One particularly usefull skill is knowing “How to Test a Transistor” using a Digital Multimeter.
Specialized component analyzers exist to do this task, but the expense can be difficult to justify for the average hobbiest.
https://vetco.net/blog/test-a-transistor-with-a-multimeter/2017-05-04-12-25-37-07
For ASTRON DC Power Supplies, you can TEST:
1.) Pass Transistors (2N3055 or 2N3771) on Rear HeatSink.
2.) Diodes and Bridge Rectifier used on the 18 VAC secondary from transformer.
3.) For Continuity and Shorts.