18Watt.com

Kind of a 2 part question here. After lurking here for quite some time I am getting ready to start a 36W build based on the many schematics and layouts available. While not looking to necessarily use one or more of these trannies, I am looking for as much info as possible. With the vast experience here someone is sure to know something. Here is a list, and part numbers if anyone has info. Part 2 of the question is, what is the best way to test transformers ? Or is there information available that will give step by step inst for testing them.

Sunn Concert Slave
PT 28-1979
EIA606-746
OT 28-4300
EIA606-740

Wurlitzer Model 44
PT 18453
OT 18451

Thanks for your help
Bruce

First things first when it comes to trannies--did those two you mention come out of tube equipment? If not, they are virtually useless for any tube type guitar amp. If they did come from tube equipment, what were the tubes used? That's a good starting point as to what you can build out of what you have. Let us know.

The Wurlitzer part numbers came from a 195? organ. Powered a pair of 6L6's.
The Sunn was not a tube amp.

Bruce

Ok, so the tranny from the Wurlitzer is usuable, but the other one (from the Sunn amp) is not. It's been my experience that salvage operations like this are very feasible, and make excellent guitar amps--if you don't stray too far from the original tube complement. SO--That Wurlitzer trannie is likely going to put out too much voltage for an EL84 amp, so you should stick to a 6L6 amp. I'd normally suggest a Bassman type amp, but you're here looking for that Marshall tone (otherwise you wouldn't be here ) Do a search on this site for "Heavy IIb" It's basically a Lite IIb, but using 6L6's instead. There are a few changes made to the standard Lite IIb circuit to better suit the 6L6's. And if you don't like it, you can always tear it apart and build a JTM45. Do you have the matching output transformer that came with the Wurlitzer? I hope so--that's half the battle. Keep in mind that a pair of 6L6's is quite a bit of power, even with cathode bias, and is going to make a LOUD amp. You may want to look into some kind of attenuation to keep things sane.....

I do have the set of trannies from the Wurly. Tone is not as important as getting through the first build. I could go the kit route but find I would learn much,much more salvaging parts from a lot of old equipment I have around. For the most part I understand the concepts and theories of the tube amp but for some reason I just can't grasp the transformer concept. I know it is pretty straight forward but for some reason throws me. I am OK with the idea of a Bassman type amp for a first build. I suppose I should find a schematic matching the trannies as close as possible and start from there.

Bruce

You say tone is not as important as getting through the first build. Never under-estimate organ trannies, my friend!! You WILL have an awesome amp out of that trannie set!! While you are considering the Bassman, also take a look at the Pro and some of the early Twins. Do a google search on "Fender Amp Field Guide" There you will find almost every Fender schematic you would care to think of. I would suggest you stick with cathode biased power tubes for a first build--it's simpler, yields a great tone, and automatically takes care of any minor tube variations.

With a power tranny, it needs to be beefy enough so that it doesn't sag under load of the circuit. If it does, your whole power chain will be stressed and the tranny will run hot (physical temperature), potentially leading to premature failure. This can have a very direct impact on tone. You want a tranny that will stand up to some abuse without flinching.

Organ trannies are often quite nice for guitar amps (someone else alread noted this). For example, I've got one with a filament supply rated at about 9A. This tranny is really too big for a typical guitar amp -- over 10 lbs of iron. Maybe, someday, I'll build something with an octet of EL34's or something and use this tranny.

While there are ways to test the transformer for it's mA capacity, many folks (including me) cheat by guessing based on the equipment it came from. Orphans (unknown origin or no schematic if already pulled) are problemmatic and need to be tested under load. So, this is a long way of saying your Wurlitzer is probably going to work well. SS power supplies are much lighter duty. Ebay the Sunn tranny.

Similar stuff applies to an OT. I'd try that one from the Wurlitzer to see what it does. There is good reason to expect good results if it otherwise matches your build for impedance.