Vibrato Erratica on Super Reverb?

[Karl Oberlander]

I have a B.F. Super Reverb that is starting to exhibit s strange phenomena. When I turn the vibrato on it starts to vibrate and then intermittently doesn't. I mean it isn't consistent or regular but sort of random?
I changed out the 12AX7 and it still did the same thing. Anyone know what causes this and perhaps what a cure might be?

Thanks in advance.

Kobe

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Gibson D-8 Console Grande
Stringmaster T-8
Fender Super Reverb

[Ken Fox]

Things to consider:

The vibrato circuit is totally dependant on a working footswitch. The switch applies ground to the vibrator oscillator and starts it. An intermittent footswith (bas cable, bad cable solder connections or bad switch (usually just needs cleaning) can cause the exhibited problem. To test, use an RCA jack that is shorted out as a substitute for the footswitch.
There could be intermittent cold solder joints in the vibrato circuit.
The LDR (light dependent resistor) package may be about to go out. Sometimes referred to as the tremolo "roach".
There are any number of other things that could be wrong and would require a tech to troubleshoot.

[Bob Metzger]

Alot of guitarists would pay big money for that 'random' sound.

Sounds like the optoislator. Use a dummy plug (RCA plug, hot and ground connected) to troubleshoot the on/off pedal and wires. Check in and around V5 for burnt resistors or broken cap leads. I'd replace the opto, caps and electrolytics and measure the resistors and then most probably, all will be well. Unplug the amp from the wall AC and discharge the filter caps first before putting your tongue on anything inside.

Bob M.

[Karl Oberlander]

Thanks guys for the info. I was suspicious of the opticoupler and have found a new one on the web. I'll replace that since I already did the caps, etc. That will probably do it.

Thanks again,

Kobe

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Gibson D-8 Console Grande
Stringmaster T-8
Fender Super Reverb