[Heathkit] Restoring HW-101: S-meter + tone in audio questions

[Alex]

Hi there,

I recently acquired a Heathkit HW-101 and I'm in the process of 
restoring it. So far I have replaced a handful of resistors that were 
out of tolerance, and also replaced some with higher power resistors. It 
seems to be working OK on 80 and 40 meters (RX & TX), but the higher 
band I select over 40 meters, the less TX power it delivers and also 
sensitivity is reduced. I'm not too worried about that yet.

To be able to zero adjust the s meter I had to apply bulletin HW-101-67 
which calls for the replacement of a few resistors so that one side of 
the s meter gets closer to ground potential. Now I can get the meter to 
go to zero, however, it takes about 20 minutes or so to get there after 
the rig is turned on. First the s meter will show over S9+60 when the 
rig is just turned on and then it rapidly drops to say an S5, then it 
takes a long time before it gets to zero. Does anyone tackled this 
problem before and could give me a hint?

I seemed to me that maybe the AVC circuit would have a problem, but 
things seem fine there.

Another problem I have is that there's a slight but annoying hum on the 
audio even with the AF control all the way down. It sounds kind of like 
an open ground or ground loop hum. I did check the grounding of all 
boards. When I switch the rig to CW I also hear a 1000Hz tone, again 
even with the AF turned down. One of the service bulletins suggests an 
open capacitor in the power supply, but that does not seem to be the 
problem. Any idea what could cause these problems?

73,
--Alex KR1ST
http://www.kr1st.com