[Hallicrafters] "The saga of an SX-62A"

[William D Dunkelberger]

I recently posted a request for some help on a couple of problems with an
SX-62A. I received 1 reply and that said to do a total recap. Well I
guess there are pros and cons to that as I've seen here, but I happened
to have a complete new set of orange drops from AES that I had gotten to
do an SX-42. So since these are almost the same, I did the complete
change out, except for C11 and C25 which are buried in the front-end, and
C111, C113 and C116 the can electrolytic. No hum noticed so I’ll do those
when the time comes. I also changed out 3 out of tolerance resistors. But
the thing still had the distorted audio and no audio on FM.
So I’m getting ready to do some voltage checks. Since I had a complete
set of NOS tubes I decide to substitute tubes and see if things got
better. When I pulled V8; the 6SG7 Limiter and AM detector, the silly
things started to play like no tomorrow!! Since when will most radios
work without all the tubes? Now the voltage measurements began and on the
grid pin 4 was about 130 volts. Tracing the circuit it looked like B+ was
coming through L2 the IF coupling coil from the plate of V7. I pulled the
wires from the L2 can and the VTVM showed continuity. Looks like the
internal coupling/blocking capacitor; C88 a 100mmfd (pf today) was
shorted. I was so I replace it and now the FM works, the distortion is
gone, and it makes rated audio output. I then proceeded to do the
complete alignment and this old girl is very very sweet again. 
The SX-42 and 62 use audio derived AGC and does not have a separate AGC
detector, so at first I was miffed as to why it acted like the AGC wasn’t
working, but I couldn’t figure out how it was obtained. Turns out that
there was no AGC and the limiter was in la la land also. Was a bit of a
shock when it worked with V8 pulled out! Any way maybe this is one for
the reflector "Hints & Kinks" I’m not the SX-62 expert, but I understand
them a lot better now. Good luck all and thanks.
73, David
W9CTJ since 1961
VIntage Radios Redone and Operated!