[Heathkit] Heathkit HW-100 nightmare

[Dick KF4NS]

I have NEVER given up on a repair but this disaster has me climbing
the walls. There have been so many snafus that I could not count them
all. The first thing happened when the HP-23A went into the
self-destruct mode with the rig setting on the bench in RECV mode
while I was out of the room. The breaker in the PS failed to trip and
took out the ICL (current limiter), the diodes in the HV, B+ and LV,
leaving the supply in the shorted condition. (I since replaced the
breaker with a slow blow 3A fuse).

I restored the HP23A using upgrades for everything. The damage done to
the rig is still being traced after two weeks working on it. I never
saw so many complex, seemingly endless number of
associated/unassociated troubles. (not counting pilot error)

First the rig lit up but nothing worked. I found 3 shorted and/or grid
emission conditions in the tubes. Another 4 were just plain weak. All
were replaced according to all known criteria. Next thing I found was
that the BIAS could not be set, adjusting the pot (which tested good)
would only give me about 30ma max, then it started pegging the needle.
All xmit tests made in tune mode, finals ok but swapped anyway, level
pot at full ccw and pot ok. Neutralization was not touched. Then the
RF gain indication on the ALC meter started dancing around. The pot
could be set at full ccw and still have full RF gain. The pot tested
ok. Trying to trace out the bias is a very difficult route and a
total nightmare. It is like a maze, going everywhere. I realized the
connection between the bias and the RF gain trouble so that explained
that coincidence. I then decided to do lots of voltage tests and
resistance tests from the charts in the manual. Nothing too unusual. I
started the alignment of the receive section and quickly discovered
that there was a major defect somewhere when the het. osc. alignment
would not hold as I switched from band to band. It is there and then
it is not there as set and read at TP1. I cleaned all the band switch
contacts again and made sure all contacts were making good contact. If
I jiggled the 3 coil boards and there was surely an intermittent.
Found one coil lead loose, one wire lead to the driver plate board
loose and resoldered both.

I began looking for anything in the huge bias string but no luck. Then
I began checking all wire and component leads everywhere for bad
solder connections. Then a further inspection and some voltage
and resistance checks in the coil areas. I accidently shorted out the
100 ohm that runs external and connects between the driver grid/driver
plate boards, with my meter probe. Sparks flew and the resistor split
in two and I did a dirty in my pants. My bad, as the kids say.
Replaced that resistor.

Then I decided to get back to the receiver section again and aligned
the het. osc. coils again. They seemed to be holding. Heard some
crackling in the audio. Banged on everything from tubes to pots and
variable caps. Kept getting closer and finally realized that the CXR
null pot was the culprit. Got a new one from the parts box. Now the
receiver was really playing good, very low noise and good strong
signals. I decided to try tuning up again since the rcvr was working
fine. As soon as I raised the drive level, the relays began
chattering. Ten watts was all it would allow. This again points to the
bias situation.

Next, the evil black cloud over my house appeared again. As I turned
the rig on it's side to measure the actual bias voltage on the finals,
sparks flew from the power cable connector on the back. Turned
everything off and found that the ground female pin in the cable broke
and shorted to another pin. Repaired the cable and glued the cable to
the connector so no more twisted cable breakage. Turned the rig over
again and some pieces of black material with threads on it fell out.
Oh no, a broken coil slug! It is the het osc coil for 80M. With the
top slug missing, it will not tune up on 80M or 40M. Nothing but relay
chatter and full drive even with the pot full ccw.

I QUIT, I AM GOING TO BED! Anyone have a spare slug laying around for
my  80M het osc coil?

73, Dick KF4NS
St Petersburg, FL 33714 USA
Keep The Glow!