Excellent info, Butch.

I'm keeping this for future reference!

Don't know for sure where I'll be able to get any needed parts here
insemi-rural west-central lower Michigan, since there are no electronics
stores in our area.

But, maybe I'm over-thinking the problem.  Will take it one step at a time.

Happy Thanksgiving to all!

Tom Behler: KB8TYJ


-----Original Message-----
From: For blind ham radio operators [mailto:[log in to unmask]]
On Behalf Of Butch Bussen
Sent: Wednesday, November 25, 2015 11:21 PM
To: [log in to unmask]
Subject: Re: Power Supply Update

These are not all that hard to trouble shoot, much easier than a switching
supply.  Put a load on it if you can get a 12 volt bulb, or key your radio
into a dummy load and check voltage at radio and at supply, compare voltages
on transmit and receive.  After you've run it a while, feel all 4 pass
transisters and see if they are similar in temperature.  Most of the time
these short, but not always.  I've worked on many of these over the years
and used them when I sold commercial radios.  The 723 chips are often
socketed, not always, so not bad to change if they are.  Pass transisters
are also usually socketed so easy to pull and check, just note the pins are
off center from the holes in each end, so they only go in one way.  If I
remember the pins right, hold the transister with pins toard you and closer
to the mounting hole on the right.  The case is the colector, bottom pin is
emiter and top pin is base.  If you don't have a transister tester, you can
check with an ohm meter.  Think of it as back to back diodes.  These are n p
n transisters, so check base to emiter and base to colector.  With positive
on base, should show like a forward biosed diode.  Reverse leads and should
show open.  From emiter to colector either way should check open.

Hope all the above makes sense.
73
Butch
WA0VJR
Node 3148
Wallace, ks.