Fender Deluxe Reverb (1971) POWER LOSS on 1 Channel

[Pastortom]

The amp has recently had a full electrolytic upgrade, and tone caps throughout....plate resistors.....mostly new components..... All tubes check at over 85%..... All pre-amp tubes are in correct placement..... BUT, the 'reverb' channel is running at about 1/3 output power, and will distort a signal terribly the higher you turn up the volume pot..........  The 'normal' channel is crisp and clean, and tons of power......Reverb and Vibrato are working flawlessly, but an overall power loss that makes the reverb channel worthless.


The circuit board is dry, no crud underneath to interfere with circuits.....tried lifting the board a little and retested....no difference.  I also swapped the pre-amp tubes (1 & 2)....no difference........


WHAT GIVES ??   

[sluckey]

Was it working OK before you fixed it?

[Pastortom]

Yeah, it worked fine with the upgrades mentioned....all normal.  THEN, it sat around for a year or so, and developed some "white noise" and distortion on the reverb channel when I went to use it again.......For total lack of time, I sent it to a tech and had him take care of it, and it came back as it is now.  He cleaned up the noise, put in a couple new 12AX7's, and voila'.   The normal channel is a BEAR, and the main channel is a wimp....an incredible distorting wimp.       

[HotBluePlates]

Ideally, you'd have a listening amp (follow link, scroll near bottom) to find where the signal stops its proper progression through the circuit.

Most likely, something is partially-shorted somewhere or there's a cold solder joint.

Anything which has been touched or altered on the reverb channel from the amp's stock condition is a potential suspect. The listening amp would help localize it faster than inspect-n-guess.