Vibrosonic amp..

[Amptech47]

This one came to me with main fuse blown and on opening found plenty of cowboy fiddling done with silicone sealant bloted on the tag board and slap dash wiring...so down to work and looking the schematic up found 2 different types being 100w and 135w types, this one being the 135w type.

Someone had removed the master volume switch function via cutting the cables and removing the 12k resistor, next they soldered on v4 pin Kathode with a 820 plus 2k2 and parallel wired a 220uf cap across it to ground and pin 8 with 820 ohm with 100uf to ground.

The circuit drawing shows pin 3 and 8 linked together and shared 820 ohm with 20uf across it to ground.

I've put the amp back as the spec circuit and removed all the mess and mods.

These amps look alot like the fender twin reverb.

Anyone seen or spent many an hour putting things back to stock after the youtuber wannabe tech has had a go.

[Leo_Gnardo]

These amps look alot like the fender twin reverb.

Anyone seen or spent many an hour putting things back to stock after the youtuber wannabe tech has had a go.

Yes they do. And yes I have. Actually in times before YouseTube (wow that was the good ol' days warn't it granpop???) I had to tackle any number of hack repairs & mods. Surprisingly, or maybe not, some came from Cesar Diaz. Including eventually his own tweed Pro. That was @ 2007, after he had passed away. And... when YT started. There was another mad mod man in New Paltz NY as well. Everybody who had an amp butchered by him came to me to have their gems restored to normal.

[Amptech47]

Leo Garden, thanks for your reply and I've plenty of amp repairs stroys over the years and I've uses to teach colleagues on troubleshooting amps.

Kind regards to you.

Amptech47.

[drewl]

One of the worst I had was a Marshall Silver Jubilee 100w head somebody hacked by cutting traces, removing parts, tacking in others, it sounded horrible.

A $1000 amp ruined.

I didn't even bother to figure out what they were trying to do.
Just ripped it all out and put back to stock.

[The Dude]

I've had many, but the one I remember most was a Quad Reverb that was unrecognizable under the hood. I did the same- ripped it all out and put it back to stock.

[g1]

How about in the 70's & 80's when occasionally people would completely gut vintage tube amps and change over to fully solid state circuitry.

[The Dude]

It was the thing to do back then. Solid state was the newest/coolest thing. Remember all of the 70's amps that proudly displayed a "Solid State" logo on the front?

[vintagekiki]

These amps look alot like the fender twin reverb.

Schematics for SF100, SF135 models is identical only difference between the models is in the number and type of used speakers.
Fender Twin Reverb SF 100 Schematic
Fender Twin Reverb SF 100 Schematic Mastervolume
Fender Twin Reverb SF 135 Schematic

Vibrosonic Reverb difference from other fenders only in that it has a 1x15" speaker
https://en.wikipedia.org/wiki/Fender_Vibrosonic_Reverb


1)
The CBS45 (70) models different from the SF100 (135) models only in PT, OT and spkr. Schematics are the same.
Fender CBS 45W Super Pro Bandmaster Reverb Schematic
Fender CBS 70W Super Pro Bandmaster Reverb Schematic