Thunderbass amp parts needed (output transformer)

[Timi]

Hey folks, I'm looking for a replacement output transformer for an early style (8417 output tubes) Thunderbass head. Anybody got one, or a Thunderbass in non-functioning condition for parts?
Thanks-
Timi
ps feel free to get me directly at shurfyne@gmail.com

 

[capnjuan]

Hi Timi; good luck in your search ... there are far fewer 8417 models than there are 6L6 models. A couple of thoughts ...

1. You might ask over on Doug Hoffman's Amp BB whether a 6L6-version OT will work instead.

2. Also, you might contact Mercury Magnetics and ask them the same question and whether they could dupe the old one.

I don't begin to understand how a pair of 8417s running at 400V on the plates could crank out 100 watts while a pair of 6L6s running at 460V only produced 50 watts ... but there are a lot of things I don't understand. :?

If you need schematics for both versions ... 8417 and 6L6, send me a PM with your email addie ... I'll send them to you. If you do the Hoffman or Mercury bits ... somebody there might want to see them too.

Hope you get your amp running.

 

[Timi]

Thanks for the reply Capn!

I have considered Mercury.. I'm sure they would do a great job with it... just had them do a replacement OT for an Ampeg GU-12 and it does sound sweet.

For the T'bass I think it would look to run about $200+ at Mercury, so that's why I'm looking for other options... who knows maybe somebody's got one for me! If not, maybe I'll let it go to somebody up here for a good price as a project. The 8417s I have in it were recently acquired and in great shape... worth something for sure! I did have a replacement OT (Fender-made I think?) in there for a bit, but the sonic fit was not right... it lacked the brilliance of the original Guild and made a harsh high-end clipping sound when pushed even lightly. I really think it needs one with the ORIGINAL specs. I got rid of that imposter because the sound was sad compared to the original!

Anyhoo, you can send schematics to shurfyne@gmail.com. Thanks for the offer- those will come in handy! I miss having this amp up and running A LOT. Such a great, clear, ballsy tone!!!
much appreciated-
Timi

 

[capnjuan]

Hi Timi; email w/ schematics attached on its way now. Good luck searching for a parts donor amp ... and you need to be a little careful; there are no identifying marks, parts, gadgets, badges ... nothing, with the tubes out, to distinguish the two models; they are functionally identical.

Depending on how sleuthy and tech-savvy you are, if you compare the power supply and bias circuits schematically and physically, they aren't the same so if/when find a maybe, you can ask the seller what value caps/resistors are in certain places in the amp; that's the only way I'd know how to distinguish whether a burned out hulk ever hosted 8417s or not.

But having the schematics, I suggest you ask the question on the Hoffman Board; they are the brightest, least preachy, most helpful people ... if you're modest, they'll fall all over themselves trying to help you.

Good luck!

 

[Timi]

Hey it's been a while since I started this adventure, but have finally reached a solution to my Thunderbass output transformer dilemma. In case it benefits anyone who comes here in the future with a similar prob, here's what I went with:

http://www.classictone.net/40-18039.html

It's a Marshall JTM45-style OT from Classic Tone, made by Magnetic Components. The great news is it sounds amazing. Gutsy, big and transparent like the original, but louder. Gorgeous tone, not to mention taps for 4, 8 or 16 ohm outputs. My Thunderbass is back and badder than ever! SO psyched I stuck with it. I've got it powering a '59 JBL D140F (8 ohm) at the moment. It's heaven. The Classic Tone transformer is awesome, and a lot cheaper than Mercury magnetics too. So far, so good and it seems very stable after playing it for a week. Alright, cheers, off to rock more Guild T'bass.

 

[Default]

Glad to hear it, Timi! Audio clips are always welcome too!:victorious:

 

[Timi]

I'd love to do a sound clip or two of this for you. Is there a way to attach it here, or do I just need to link to it somehow?

 

[Default]

You have to put it up on alonetone or some other hosting site. Lokking forward to hearing the tbass in full roar!

 

[Timi]

Well here's a basic recording of the amp... uploaded to my band's site. I left it in aif format hopefully to be better sounding than an mp3... most browsers should play it?

http://kitetothemoon.com/mp3/Tbass-Jazzmaster1.aif

It's simply the Thunderbass normal channel at low volume (9:00) with my old Jazzmaster. I doodled a bit with each pickup, the middle and rhythm positions too. The amp is pushing a '59 JBL d140F speaker, and I used an Audio Technica 4040 mic to record it with Protools. There ya have it. I'm not sure this is the "roar" of which you spoke, but it shows the amp's sweet tones. Maybe I'll crank it and do another clip soon!

Cheers!