1976 Bassman 50 help

[Lizard King]

I recently picked up a 1976 Bassman 50 with MASTER VOLUME and a twin 15 cab. The amp sounds good but, as it's not a "vintage" model I'm thinking of making some mods. The problem I'm having is I can't find a schematic or chassis layout for this model. I can follow schematics and know which end of a soldering iron to pick up but I'm not so expert as to look at the guts and tell what every component is doing. There is no tube chart. I dated it by the transformer stamps.

I'm looking for that cool 60's blues/Ventures/Beach boys sound. I also have a Crate Vintage Club 30 which I'm playing through until I get finished with the Bassman.

Does anyone have any idea what circuit I have or any suggestions for mods.

Thanks.

[petemoore]

http://www.ampwares.com/ffg/
Does it look like any of these?

[Lizard King]

I've looked at all of those. None of them have a master volume.

[Paleo Pete]

Look at the link above again, the Bassman 50/70 has both schematic and board layout. The board layout may help you figure out if it's the same circuit with a master volume added, which wouldn't be that difficult for them to do. Some people remove the master too, also not that hard to do. I would, I don't really like a Master Volume much. or maybe I just like my straight Super Reverb and Champ too much...

You might also look at some of the other 50 watt 6L6 amps, I'm willing to bet you'll find one that's close somewhere.

That said, there are a couple of things that are pretty standard mods on silverface amps, if I can find the links...The first thing I did with my Super Reverb was change a cap to cut the bass down to something usable. Stock, it had way too much bass - loud, boomy and barely conrollable with the bass knob on 2. I swapped one cap for a different value and it brought the bass back into controllable, good sounding range now I run it about 6 or so and it's great.

The only other change I made was to remove the 2000pF caps on top of the power tubes, those supposedly suck a lot of the really high end chimey sounds out of the amp, and routed the resistors to the side of the tubes so they don't get cooked every time I play the amp.

There are a couple of other things you can do, I didn't want any major changes, just get some tone back. Check Here for a good description of the differences between silverface and blackface amps, and some links to other sites that go more into modifications. Tales from the Tone Lounge is a really interesting read too, and Blue Guitar Pages has some good info and lots of links to shematics etc.

[Lizard King]

Thanks for the info. I guess I'm too rusty (my tube theory came in Air Force school 25 years ago and it was only a week) or probably too lazy to actually look at my circuit and compare it to different schematics.

Guess I'll have to bone up if I'm serious. I've heard there are hinkey bias feedback circuits that should be removed as well as the cap values you mentioned. I don't use a master volume so it's no problem removing it. I just figured if I could find a schematic with a master vol it would probably be mine since they didn't seem to make very many of them before they went ultra-linear.

I saw the blue guitar site. That guy seems to gut the entire amp and start over....seems a bit much.

I'm thinking a tube rectifier kit would be easy to install - Torres has some. Then perhaps an effect loop; there are so many jacks on the front panel, might as well use them up - though now I jumper out of channel one into channel two - suppose I could do that internally to get another stage of preamp.

I picked the unit up cheap and wanted to play with it as I have a Vintage Club 30 that I currently play through. This is gonna be my winter project.

Thanks again!