'68 SUper reverb anomalies

[Underwood]

  I've been working on a '68 super reverb and have noticed a couple of strange things. First is that on the vibrato channel, there is not any or barely any volume when the treble is down. Second, I plugged into the normal channel and was still able to use the reverb. Before I go through the whole schematic I was wondering if this rang a bell for anybody.  THANKS!!

[sluckey]

First is that on the vibrato channel, there is not any or barely any volume when the treble is down.

Could be normal. Were the mid and bass also turned down low? All the Fender Treble/Middle/Bass (TMB) tone stacks will totally kill the signal if all three knobs are set to zero.

Second, I plugged into the normal channel and was still able to use the reverb.

It's been modified. There's a very simple mod to enable reverb on both channels. See attached...

[Underwood]

Thanks. I will check out that reverb mod and see if that is what was done. As for the other thing, the bass was on zero, but the middle was not.