[Heathkit] SB-303 4th results

[kiyoinc at attglobal.net]

Tuned around, with the gain turned down, the hum is deep. This is on an 
old Radio Shack Minimus-7 speaker which has good bass response.

Checked power leads with Tek, there's a 88 mv 120 Hz sawtooth on the 35 
VDC line.   The other leads look OK on the scope.

The rising edge of the sawtooth is near vertical  and the trailing edge 
tapers.  I'm guessing that the main 2000 mfd capacitor is bad.

Put the tek on the audio out line, the AC hum is a sine wave and not a 
sawtooth.  It is very visible when the gain is turned down.

Checked the detector out connection.  It looks good, no AC visible.

Tuned around 40 and 80.  Good strong signals but the LMO is definitely 
dirty.

Checked the dial lamp voltage again.  Looked at the schematic.  The dial 
lamps are daisy chained.

As recommended, I'll take a look at the electrolytics in the audio stage.

de ah6gi/4