gerald guerrero said:HI. Can anyone help me with some tech advice. I have a friend who is going to help me convert a Tube PA to a guitar amp. It is a Lafayette model PA 675(a).We dont necessaraly need a schemetic, however my friend isnt certain about the Power tube configuration. There are 3 sockets , two of them are marked EL34. The third on the end in the pics,wothout any resistors tied to the socket is unmarked, and has seperate taps from the the EL34's directly out of the transformer. This doesnt appear to be a power tube, according to him. He cannot figure out waht it may be. It is definitly a socket similar to the two marked el 34 with seperate Power tansformer taps. Any help on this would be really appreciated. I think an EL34 PA amp would make a really great Guitar amp conversion, but we have reached an impasse with no available schematics. Ive searched just about everywhere. Here are the pics...
This looks more and more like I'm right that this amp ran 2 rectifiers. The 5y3 would run the preamp stages and maybe the screens of the EL34s. There would be another rectifier like a 5U4, probably in the socket to the left of the 3 sockets in the upper left of your picture.gerald guerrero said:Well, According to onesponce from another board , it appears it could be a preamp out socket or something , since it is a PA amp. They usually use different sockets, but its possible that a regular tube socket was used. One thing I forgot to mention is that ther is alreadya rectifier tube in the preamp section. Its a 5Y3 , which someone mention is woefully inadequate for two EL34's. If I could only find this schematic, but ive looked everywhere, and noone has it.
My Masco MA50 originally used 2 5U4's in parallel, although I only use one since I converted it to guitar amp use (I like the sag )Wild Bill said:It's not all that rare to find 2 rectifiers in a power amp. I've seen it in some Western Electrics, Bogens and Stromberg Carlsons.