1965/6 Guild Thunderbird

Last week I picked up a Thunderbird that, according to speaker and pot dates, looks to be from late 1965. It's the 1x12 1x8 version. After scouring the board and other parts of the internet I cannot for the life of me find a schematic - hoping someone here can help me out!

I haven't given it a proper photoshoot yet, partially because it's in pretty poor cosmetic shape. Looks like someone replaced the cabinet at one point, and I'm honestly a little scared to see what's under the tolex (vinyl?) should I want to recover it and make it presentable. The guy I got it from had replaced the disintegrating MDF baffle with a piece of 3/4" plywood, and it's not a pretty sight. I guess it could be worse -- I bought this as a project amp, and it looks to me like it has never been touched under the hood -- all original tubes, no sign of a cap job, original speakers, etc. Sounds pretty good if you keep the master volume down, but if you turn it up you get a lot of noise that I assume to be the filter caps.

All the parts needed for rehabilitation have been ordered, but it would be nice to have a schematic to start thinking about getting the tremolo working again. If anyone has advice, let me know!

Welcome. I'm not sure what schematics are stashed where but hopefully someone who does know will be along soon.

Right now, I'm kinda scrambling around and I don't have my new digs set up yet. IIRC, the T-bird has a 6gw8 driving the reverb through the 8" speaker. When you change the filter caps, you might want to look into changing the plate resistors, especially if the values have drifted. They can add to noise also.

That's the one. I see PM mentions of a schematic, but haven't seen anything as an attachment or link. I have a feeling that there aren't many of these things around, so it's understandable if there isn't much documentation either.

Regarding the plate resistors, that's going to have to be step two in getting things up and running again. I've done a decent amount of work on smaller amps, but never anything this size (mostly Champs and similar). If there's still noise after the cap job, I'll look into other sources. I do like that there are bias pots and other nice features inside tough -- most amps of this era lack those types of things, in my experience.

Btw, Guild amps of that vintage had particleboard cabs. If you get it to the point where it's a keeper, having a cab made for it would be doing it a favor.
I do know a guy who has a similar t-bird and he might have a schemo for it, but he's overseas at the moment.

I've made cabs before, so it's not out of the realm of possibilities. I'm pretty sure the whole thing is just butt-joined plywood, but it's not clear without ripping off the tolex/vinyl how they joined things. If nothing else, it does look like the right dimensions, so they probably cut the ply using the MDF as a template. I was originally interested in the amp because of the price and the option of flipping it for a profit, but with the way it sounds it could very well be a keeper... As of now, even after ordering the caps, I have $205 into it.

Did you see this partial schematic?
http://www.prowessamplifiers.com/schema ... Tubes.html

If you're doing a full cap change, it should include the caps in the trem circuit. Maybe that will get it working. Good luck!

Is this a T1 RVT ?

Isn't that just for the later version? I assume there were a lot of changes between these, partially because of the speaker setup, how the reverb works, etc. This one has 2x 7591A tubes in the power section, and I believe the later ones used 6V6, no?

Is this a T1 RVT ?

Click to expand...

Nope. V1 Guild Thunderbird.

RutherfordBrave said:

Nope. V1 Guild Thunderbird.

Click to expand...

Curses ! I have a T1 RVT schematic.

Guild only used 6v6s in the earlier amps. The 30 watt amps all used 7591s.

I think I have he right schematic(s) for you. PM with your email address and I will send them to you in a few hours. Harry

Schematics sent and received. Hope they help out! HH