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.