Hi Guys,
I am re-posting the info on Thunder amps that was I posted under SFIII's Superstar discussion which raised a few questions about the Guild Thunderbird and Thunder amps. It will make the info on the Thunder amps easier to find in the future.
A few comments...
The Thunder 1 and Thunder 1 RVT are similar but not identical less the speaker driven reverb circuit. A good tech should be able to use the T1 RVT schematic to repair a T1 especially the power section.
The differences between the T1 and T1 RVT beyond the Reverb circuit is the following:
Inputs: The T1 has two inputs: Normal & High Gain, The T1 RVT has three inputs: Mic, Normal and Bright.
Tremelo: The T1 has a Tremelo ON/OFF switch on the front panel; The T1 RVT uses a hardwired foot switch to turn the Tremelo On/OFF. Both the T1 and T1 RVT have a Tremelo speed control. The T1 has a small POT burried back inside the amp housing where you can adjust the Tremelo strength; the T1 RVT has a Tremelo Strength control on the front of the amp next to the Speed control.
Layout: The T1 Tremelo controls are near the Inputs; The T1 RVT has the Tremelo controls near the Volume/Pull For Bright control.
I used to have a T1 schematic and will see if I can track it down. Believe it or not I sent a snail mail letter to Fender a few years back and I got a nice email reply stating they did not have a lot of info on Guild amps but they had a few schematics and they emailed them to me. Unfortunately I never backed up my files and lost them when I had a harddrive failure.
The amp capnjuan described is a Thunder amp and not a Thunderbird amp. Very different amps although the early Thunderbird amp did use the same reverb circuit as the Thunder 1 RVT. Additionally the way you described your amp it sounds like one of the early models (There were 3 different cosmetic styles of Thunder amps between 1965 and 1969. They also have a few subtle alterations to the cabinet & chassie. The most notable is the later amps had a power polarity switch.)
The grill style of your amp is often refered to as the "fish scale" grill cloth. The color of the grill cloth when new was actually a bright silver. With exposure these grill cloths eventually turn yellowish. I have owed a few T1 amps that came with the origional cover and were cosmetically like new. I couldn't believe the stark silver grill cloth cover of a closet kept amp!
The Thunder 1 amp is a great little amp. However if your amp is really beat up and it is going to cost a mint to fix it I would recommend you pick up another one and sell yours for parts. The T1 RVT's pop up on ebay pretty often. The usually range between $300-$400. Keep yours for parts and when your satisfied you got one working then sell it to some who is looking for parts. Often the reverb tanks get one or more springs broken.
Additionally, I saw your earlier post and you correctly listed the proper Reverb power tube as a 6BM8/ECL82. I was incorrect in my tube list in stating the Reverb power tube was a 6GW8. My mistake!! I hope I didn't cause a problem for anyone.
With regards to 6GW8 availability...I have not had any problems finding these tubes on ebay. They may not be made anymore but their are still readily available.
The T1 and T1 RVT are great little amps. However they are not for everyone. My preference is the T1 RVT model. The Reverb makes quite a postitive difference on this amp. Many people find the amp to be too clean sounding. This is true at low levels. However there is a time when that is the tone I am looking for. When you crank up the T1 amp, with a lot of treble, it breaks up with a much more agressive tone than EL84's or 6V6's. It's a uniques sound to the Thunder amps. I always recommend that better tone out of Guild Thunder series amp is achieved with a speaker swap. The stock Oxfords don't do the amp justice.
Finally, the Thunder amps can be very bright and have a strong mid tone. However they are a bit muddy sounding at the lower frequencies- especially when cranked up. I tried to clean this lowend tone up with various speaker substitutions but I could never tighten up the low end tone. It seems to be intrinsic to the amp. However, this low end tone issue is not a major detractor.
The Thunder amp is best used in a small room or studio. A few years back I was talking with Jay Pilzer about Guild amps (I bought a Guild Reverb Converter off of him.) He told me his son took a Thunder 1 RVT to a studio in the Nashville area and when the amp was heard by various guitar players they were really impressed. There seemed to be a lot of interest in owning this model.
Thanks,
matsickma