SF Vibro Champ vibrato not working

It worked at one point a few years ago. But now the intensity knob does nothing. I have done various small repairs on it. Any ideas of what the problem could be?

The first and easiest check, being as it worked the last time you used it, would be to spray some contact cleaner onto an RCA plug and insert it into the footswitch jack then give it a couple of twists. One of my Princetons tends to get enough oxidation on the jack once a year and its enough to short the jack and turn the tremolo off. Just putting a plug into the jack will usually clean it well enough to start it working again.

If you did some soldering near that portion of the circuit and never tried the tremolo afterwards those joints would also be the first area to check.

Have you tried another tube?
You can just swap the two 12ax7s if you don't have a spare.

The first and easiest check, being as it worked the last time you used it, would be to spray some contact cleaner onto an RCA plug and insert it into the footswitch jack then give it a couple of twists. One of my Princetons tends to get enough oxidation on the jack once a year and its enough to short the jack and turn the tremolo off. Just putting a plug into the jack will usually clean it well enough to start it working again.

If you did some soldering near that portion of the circuit and never tried the tremolo afterwards those joints would also be the first area to check.

I'll try that.

Have you tried another tube?
You can just swap the two 12ax7s if you don't have a spare.

I'll try that too. So one of the 12AX7's controls the vibrato circuit?

Ya one is the preamp and phase inverter and the other is the vibrato.

Ya one is the preamp and phase inverter and the other is the vibrato.

Pssssst, Bobby, there is no phase inverter in a vibro champ, it is single ended:smile:.

Pssssst, Bobby, there is no phase inverter in a vibro champ, it is single ended:smile:.

Whoops! :lol:
But half of one 12ax7 drives the 6v6 right?
What is it called?

Whoops! :lol:
But half of one 12ax7 drives the 6v6 right?
What is it called?

Being as how it is just a normal common cathode gain stage, I would go with it still being part of the preamp