Incoming Supro Vibra Verb 1966 6498 VR Reverb Issues. HELP!

[cluster]

This one might be a challenge. I just got a Supro Vibra Verb 1966 6498 VR with major reverb issues. Looks like somebody has been in there and messed things up good. The result is that the reverb knob functions as a gain knob. Turn it up and the amp's gain goes through the roof and she starts to squeal like a pig. Just awful... and the tone knob also makes weird ray gun sounds as I turn it up and down. Totally bizarre. Does anybody have any idea what could be going on?? ohh, and I can't find a schematic anywhere

photos here https://www.dropbox.com/sc/tj2c3nld6...aR04nhczttpUJa

detail 2014-07-04_2014 - clusterstudios's library

and 2014-07-04_2019 - clusterstudios's library

also, forgot to mention that the amp sounds anemic and the tremolo sounds a bit wobbly..

Joseph

[Chuck H]

It sounds like someone modded it for gain using the reverb circuit tubes. Finding a schematic and rewiring it correctly is probably the best answer. If not a good one. There may be another amp model that has a similar circuit too and that might be used to glean info. The last option depends on your skills. You could just design a working circuit to use.

[cluster]

i've tried searching for a schematic but no luck. This must be a rare bird.

[Chuck H]

The Supro brand has been through a few incarnations. Concise info on different era's is a tall order most times. You may need to take notes on what looks to be stock and reinvent the rest if you want the reverb working again. But you're still a few days from a dead end. Someone may yet post with info or a schematic may surface. I, personally, wouldn't want to trouble with tracing the chassis shot photos. The wiring in that thing looks like a plate of spaghetti!

[Audiotexan]

The Supro brand has been through a few incarnations. Concise info on different era's is a tall order most times. You may need to take notes on what looks to be stock and reinvent the rest if you want the reverb working again. But you're still a few days from a dead end. Someone may yet post with info or a schematic may surface. I, personally, wouldn't want to trouble with tracing the chassis shot photos. The wiring in that thing looks like a plate of spaghetti!

Definitely good advice... and 2nd the spaghetti plate. lol

I did find a nice little site here at oldfrets that you may want to check out, and see what's close. A nice little aside, is that you've already dated yours, that will hopefully help narrow down the search on that page somewhat.

Might also help to know what the actual tube complement is if you get a spare moment to post it!
I see 6-preamp's, and the two mismatched 6L6's...

[EFK]

I'm pretty sure this is what you have:

http://el34world.com/charts/Schemati...REM-REVERB.pdf

[cluster]

Thanks Eric. Here is a shot of the tube layout: supro vibra verb chassis

12ax7, 12ax7, 12ax7, 12ax7, 12ax7, 6DR7, 6l6, 6l6

Let me know if you need specific close-ups of the chassis.

Thanks again.

[EFK]

Aack. The 6DR7. That's the reverb driver, it's a dual triode. It's probably using one of the 12AX7 as reverb recovery, or something like that. This one is probably a combination of the schematic I linked to above, and some of the later Airline amps that used the 6DR7 like the GVC-9027a or 9037a. There might be some others, you'd have to try to go through the schematics although the Airlines are usually tube rectified and (4) 6L6; but most of the preamp, reverb and trem is probably the same except the Airlines at some point went to one of the other weird tubes, I think a 6EU7, for reverb recovery. I think you're in for a tough job here, mostly because someone already dug around in there and screwed it all up, unless you can find a schematic for that specific amp. Otherwise the best bet is probably going to be to cut and paste from a bunch of the Valco schematics with reverb, try to go through the amp first and deal with the rest of the preamp and the trem, figure out where the reverb tie points are and lift those temporarily, get the thing going and then find work with some of the 6DR7 Airline schematics to get the reverb going.

[cluster]

better images of the guts can be seen here. still a mess but easier to see.

https://www.dropbox.com/sh/qiqksp4xf...rZu-rgelSE_J1a

[fdesalvo]

I'm bringing this back up to thank the OP for his generosity in publishing these pics. One of these fine amps has landed on my bench and these pics are indispensable in the absence of a schematic!.