Mid '70s Twin to Blackface Website/manual ?

[lordnielson]

Yep, I'd like to mod my old twin to blackface specs. Is there a website, pdf, manual somewhere that has a relatively coherent rundown of the procedure and components needed.

Alternatively just some of the more popular mods, like how to get rid of the boost function or perhaps the entire master section.
I have searched google and God knows how many sites to no avail.

Cheers

[Marc]

Here's a site that has a very nice schematic and lots of other tips...

http://www.diyguitarist.com/GuitarAmps/TwinReverb.htm

Marc

[lordnielson]

Good one. I've actually been there before, but I just found the schematics at the bottom of the page so that's cool stuff.

[strangeways]

This guy is funny, and there are a bunch of good ideas found here.

http://www.tone-lizard.com/Mods_and_Odds.htm

This book is great as well.

http://www.amazon.com/Desktop-Refere.../dp/0964106000

Good luck,
D.

[Paleo Pete]

Schematics and/or board layouts for most Fender tube amps at the Fender Amp Field Guide.

I'm no amp tech, but from reading through a bunch of pages about it mostly to tame the horrible bass in my Super Reverb it seems to depend on the amp. If CBS changed the GZ34 to a different rectifier tube, usually 5U4, that should mean different power transformer and voltages, complete blackfacing won't be possible, unless you want to shell out a bunch of bucks for a transformer and do a lot of work, but close should be possible. The sites listed already are excellent, a decent description of the basic differences Here that pretty much agrees with everything else I've read. I'm no expert, just sharing the results of some research.

I had some other links at one time, either I've lost them or they're on another computer...CRS sucks...

The biggest difference in my Super Reverb wa swapping out the cap to tame the bass down, that by itself made the amp sound totally different and LOTS better. Before, it was boomy and for all practical purposes out of control at 2 on the knob, after swapping one cap I can run the bass at 6 and it's the best sounding amp I've ever owned. That and removing the caps on top of the power tubes were the two main mods I did, and I had to replace every cap in it to get it to work right, electrolytic and "chocolate drops". It was dropping to half volume after about 10 minutes, like you pulled a power tube. Replaced the last of the caps, it works perfect now and has for 4 years. Made me happy, I was expecting a bad output transformer...Sprague "orange drops" went back in, mostly Sprague electrolytics. Filter caps had already been replaced by a local shop (didn't fix the problem but they sent it out anyway) and I replaced all the 1 watt resistors to stop the hissing when it idled. Sounded like frying bacon, not good onstage...

Oh, and the very first thing I did was replace the power cable, someone had ripped the ground pin out...

I can't get mine back to exact blackface specs, it's the 5U4 rectifier, different transformer and voltages, so I had to settle for the main two mods that make the most difference, bass cap and power tube caps. It's a 73 model, AA270 circuit I think, (may be AA1069, CRS strikes again but very little difference in them) CTS speakers, no master volume fortunately, and now it makes this tone junkie happy...

EDIT:
Might be some info on the master volume issue Here, if the links at bottom still work, I didn't go through them all, I'm on dialup...sorry, but I don't have two hours...or a master volume.