On Saturday, January 18, 2003 at 12:10:59 AM UTC-8, Roger Leone wrote:
Woods:

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.

In article ,
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



When you cycled it, did you turn it off and back on very quick ? The
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.

On Thu, 17 Jan 2019 09:41:03 -0800 (PST), wrote:
On Saturday, January 18, 2003 at 12:10:59 AM UTC-8, Roger Leone wrote:

I am having similar problems with my RS12 supply.

.... then you should start a new thread instead
of replying to a FIFTEEN YEAR-OLD THREAD!

On Thu, 18 Jan 2019, Allodoxaphobia wrote:

On Thu, 17 Jan 2019 09:41:03 -0800 (PST), wrote:
On Saturday, January 18, 2003 at 12:10:59 AM UTC-8, Roger Leone wrote:

I am having similar problems with my RS12 supply.

... then you should start a new thread instead
of replying to a FIFTEEN YEAR-OLD THREAD!

Some people seem to think everything related should be "kept in one place"
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

Michael Black wrote:
On Thu, 18 Jan 2019, Allodoxaphobia wrote:

On Thu, 17 Jan 2019 09:41:03 -0800 (PST), wrote:
On Saturday, January 18, 2003 at 12:10:59 AM UTC-8, Roger Leone wrote:

I am having similar problems with my RS12 supply.

... then you should start a new thread instead
of replying to a FIFTEEN YEAR-OLD THREAD!

Some people seem to think everything related should be "kept in one place"
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.

The problem is not created by people but by the ridiculous "Google
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)

In article ,
Rob wrote:

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.

I am willing to forgive people for replying to such old threads. If I
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

On 1/20/2019 9:52 AM, Fred McKenzie wrote:
In article ,
Rob wrote:

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.

I am willing to forgive people for replying to such old threads. If I
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

I've occasionally fallen into that also, replying to an ancient posting.
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

I will post to a new thread. I found this thread through a google search and didn't think it was such a big deal to reply to an old thread. My apologies.
Ross AD6OE

On Sun, 20 Jan 2019 10:15:54 -0800 (PST)
wrote:

I will post to a new thread. I found this thread through a google
search and didn't think it was such a big deal to reply to an old
thread. My apologies. Ross AD6OE

It's not a big deal. It just so happens that there's a worldwide
shortage of things to be outraged about ATM, so people jump on whatever
they can get.

In article ,
wrote:

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?

Ross-

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