Guild Thunderbird (version 1)

capnjuan

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There's one for auction on eBay here. Twin 7591s, solid state rectifier, 30 watts out with two channels (no switching), tremolo / reverb on channel 2 and an extra 'shaping' control for the tremo, separate brightness switches in each channel, Master Volume, and a choke in the power supply. Similar to the mid-60's Gibson GA30 except with trem but 8" not a 10" speaker. The several members who own or have played them say they are great-sounding amps. This isn't the cleanest example but ....

front01.jpg



Original (or in-period replacement) 12" Jensen 'EM'/Concert-series and 8" CTS ceramic speakers:

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Sides banded with aluminum and particle board cabinet covered with wood-grain shelf paper:

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sideright.jpg



Some discussion about the ...
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of Guild reverb


Once upon a way back when, there was the Guild-Peg 98RT:

98RTpic.jpg



.... which used Ampeg-esque two gain stages and a coupling capacitor ahead of the reverb can. V2A and V3A (left sides) increase the signal strength to drive the reverb can (magenta line), V3B (right side) recovers and amplifies the reverbed signal and sends it back to V2B (blue line) which functions as a mixing amp and sends the blended signal to V4A (green line).

98RTverb.jpg



The next Guild reverb amp was the T1 RVT (version 2 shown below; forward 'ears' gone from the cabinet side panels and no upper backpanel:

T1RVT.jpg



In the T1, Guild coupled the reverb can using the 12" speaker for impedance matching avoiding the cost of the transformer and a resistor and capacitor in series to damp the line voltage. To maximize the dry output, the T1 has a leg from the line to the footswitch which switches the 6BM8 input between the dry/line signal and the wet reverb signal; the 6BM8 and 8" speaker are 'always on' whether the reverb is engaged or not.

T1RVTverb.jpg



The version 1 Thunderbird does not have a line feed to the 6BM8 but continued coupling the reverb with the 12" speaker. Guild also moved the reverb can from the bottom of the cabinet to a 9" 2-spring 'tray' or 'pan' mounted in the chassis. The footswitch (green box) doesn't switch between inputs, it grounds out the reverb circuit ahead of the 6BM8. In the off position, the 6BM8 and 8" speaker do nothing and only the 12" speaker handles the dry signal.

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A cautionary tail:

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Like the T1 RVT, the Thunderbird cabinet is particle board; stable when kept dry and not exposed to lateral impact. As this stuff ages, it absorbs moisture and gets heavier and weaker. There are several instances where members having T1s or TBirds shipped to them have been .... eh ... disappointed.

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The version 2 Thunderbird in more sophisticated cosmetics and up-powered with twin 6L6s @ 50 watts, and two 12" speakers ... a force to be reckoned with.

Guildtbirdrev2.jpg
 

matsickma

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Hi capn,

The Thunderbird version 2 has many similarities with the Version 1 amp including the master volume, 7591A finals, reverb tray mounted inside the chassis, circuit cards but the speaker driven reverb was removed so both speakers now have a reverb mix. The Thunderbird Version 3 amp without the master volume control is the model with the 6L6's. It is similar to a Superstar albeit the Superstar comes with 1-15 inch speaker instead of 2-12's.

M
 

capnjuan

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Thanks Mike. Haven't yet found a schematic for the version '1.5' you mentioned but never say never! :)
 

matsickma

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Hmm.... I thought you gave it to me a while back. It is the schematic that says: Thunderbird, Superbird I, Superbird II. Ring a bell?

M
 

capnjuan

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matsickma said:
Hmm.... I thought you gave it to me a while back. It is the schematic that says: Thunderbird, Superbird I, Superbird II. Ring a bell?
Yes, I recall, and I see your point. You and I have the following Thunderbird schematics:

1. Thunderbird (V1) from Musicparts.com. 7591s, speaker-driven reverb feeding dedicated 8" speaker. The model that's the subject of this thread.

2. Thunder - Superbird I and II: dated 1/12/68 including power and heater supplies, channels 1 and 2, and the effects; trem, reverb, and fuzz. No output tubes or transformer. Reverb is transformer-fed, output to mixing amp, not to a dedicated speaker.

3. Thunder and Superbird I and II / Power Amp.-supply: dated 2/2/68. Superbird I and II power supplies including 6GF7 in the Sbird II supply. Complete output tubes (7591) / output transformer for Thunderbird, Superbird I and II.

I read items 2 and 3 as belonging to what you're calling V2; 7591s with no dedicated reverb speaker.

4. Thunderbird - Superstar (the rest truncated): dated 10/21/68(or 9?). Complete including 6L6 outputs. Reverb is transformer-fed, output to mixing amp, not to a dedicated speaker.

This would be the 6L6 version / V3 ... okay ... pot's right!
 
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