[Drake] TR4-C AC Audio Hum

[WA2DGD]

Hello,
I have been using a tr4-c without any problems. I always listened using the speaker. I started using headphones and notice a significant hum with the volume fully ccw. To hear weak cw signals, I have to raise the volume to an uncomfortable level to get the weak signals above the hum noise level. 
I checked the AC4 and all the voltages are proper. I put a scope on the +250v line and can see about 2 volts p-p of ac ripple. I see the exact same waveform if I connect the scope to the audio output.
Can I simply put new caps of the appropriate values across the caps in question on the underside of the AC4 chassis? I would like to reduce the hum significantly. Are there any other known causes likely to produce this hum?
Thanks,
Larry 


--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
The reason this message is shown is because the post was in HTML
or had an attachment. Attachments are not allowed.
Please post in Plain-Text only.---