Help!-Sceptre reverb distortion/need tremelo circuit part

[MikeL]

I have a '70 Sceptre head(s.s. rectifier)...the reverb is driven with the standard 12au7 tube, but as I turn the reverb up, I get a volume increase in conjunction with the reverb increase that is progressively distorted(like a bad 60's fuzztone)that actually drowns out the "dry" signal(since the reverb is a "side chain", the tone controls don't affect the 'verb, which then gets very shrill).  I tried using a lower gain tube(12az7)but nothing changed.  The reverb pot is getting a bit hard to turn...could a bad or incorrect ohm pot create all this ugly buzz, or are there caps/resistors possibly crapping out?  I've got a tremelo problem as well; it takes a while for it to "warm up"--the intensity is barely there at first, and then just increases faintly.  The speed could be better as well.   I know that the heart of the circuit is some sort of optical plug-in thing...anybody out there have one salvaged from a dead amp that they could offer up(assuming that's the problem)?  Any guidance on both subjects would be appreciated...thanks!!!  

[Fred Cook]

Mike,

These are fairly common failure modes for the Sunn special effects circuit. (My Sceptre suffers from these problems. Had a Solarus with a dead tremolo back in the day.)

You can download schematics and service manuals from this site. Would suggest that you take them and the amp to a good tech - and keep us posted on your luck!