I recently recieved a Fender Ultra Chorus. its a solid state 2x12 combo made between '92 and '94 and at first i thought the speakers were blown. upon testing another set of known working speakers in the amp i realized it was not the speakers but the amp its self. it is producing an distorted oscillation whenever it is played. it is more noticeable on lower frequencies. i have narrowed it down to the power amp section by plugging directly into the effects return. it has been driving me nuts all day. here is a link to the schematic http://schematics.number26.org/index.php?dir=fender/FENDER%20ELECTRONICS%20SERVICE%20MANUALS%20and%20TECH%20NOTES/Fender%20Amplifiers/&file=Ultimate%20Chorus.pdf . any help would be much appreciated. thanks guys.
it is producing an distorted oscillation whenever it is played. it is more noticeable on lower frequencies
This could very well mean that the power supply filter capacitors need to be replaced. It's been almost 20 years, a cap job wouldn't hurt even if they aren't causing the issue. Check for bulged, burnt-looking, or cracked capacitors. Discharge all of the power supply filters caps.
thanks man. after looking around the web i was thinking thats what it was.
You're welcome, have a tech look at it if you are uncomfortable working on it.