Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kc3lmv on February 19, 2020, 02:06:42 pm
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I bought a organ Tube amp at an auction with the hopes of turning it into a guitar amp. After a days search I have not been able to find a schematic. The amp has a 12AT7, a 12AU7, a pair of 6L6Gs, a 0A3 and a 5U4G. The OPT is a K-58054. Photos are attached. Any Help would be appreciated. I am hoping to find either a schematic or failing that a diagram of the OPT.
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DON'T gut it! yet. what's the bottoms side look like? It's pretty easy to trace out the circuit, just go slow, ask questions, pretty soon you have a schematic. Then you have the ability to test as is. Then maybe you re-propose, or just tweak n play
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Shooter,
I'm defiantly NOT going to gut it. Organ amps have a good reputation as being good also as guitar amps. I need to figure out the wiring for the speaker and the power connections. I am starting to think there was a field coil involved with the speaker as there looks to be a power connection on the speaker socket. the bottom is rather clean. and you are correct the circuit is rather simple. If I have to resort to drawing the circuit I will. I'm am still holding out that I may find the schematic.
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was a field coil involved
could be, should be able sus that out, a field coil also acts a choke in the PS (I think)
across from your avatar is a search put in "field coil" and get the readers out :icon_biggrin:
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Are there any other numbers on the transformers? There are 3 digit EIA codes that were assigned to various companies and you can tell who made the transformer by that code.
http://www.triodeel.com/eiacode.htm (http://www.triodeel.com/eiacode.htm)
Conn used a lot of Foster transformers which are 394 for the code. They made excellent transformers so if those are what you have, you have great quality iron. Foster was very responsive to me in the mid 1990's when I was looking for transformer blueprints for the Conn I have. I think some of their old engineers were still there at that time. Many transformer companies can't be bothered such as Schumacher.
You probably won't want to use the OA2 in whatever amp you end up with unless you are looking for clean, but YMMV.
Greg