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

[SBJohnston at aol.com]

kr1st at amsat.org writes:

>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

There's a mention of this problem in the document "Improving the HW-101" 
found at 

http://members.tripod.com/NRWILLIAMSON/HW-101.pdf

He says R107 is overheating and changing value.  He recommends replacing it 
with a 100k 1-watt resistor.  Also suggests changing R106 to 33k 1-watt.

> 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. 

To fight that hum I've heard folks recommend loosening and retightening all 
the chassis hardware, such as the screws and nuts holding the boards and 
terminal strips to the chassis.

> 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?

That's probably bleed-thru of the sidetone oscillator signal.  There's a fix 
for that issue in the document 

http://members.tripod.com/NRWILLIAMSON/Hw101.pdf

which bypasses the sidetone to ground during receive.
 
Steve WD8DAS

sbjohnston at aol.com
http://www.qsl.net/wd8das
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