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I recently found a SG systems amp (cmi) , only in a “head” version, with no speakers, I guess that it originally was a combo, but has been rebuild.
I am very desperate to get some schematics for that, I haven´t been able to find any on the net. I don´t know exactly which model it is, there is nothing written on the backside of it. When I got it, the fuse was blown but after changing that it played, but I think it needs new tubes the sound is very “thin”. The tubes that were in it was a sovtek 12ax7(7025) preamptube, and 2 Sovtek EL34 tubes. I have read that these amp originally uses RCA 8417 tubes, do you think that it has been converted to use EL34 tubes, or is this maybe the reason for the blown fuse and thin sound? I would appreciate it a lot if anyone could mail me some schematics or maybe just give me some advice.
The images i have attached are not of my amp, but pics I have found in other forums, but it looks exactly like mine. Thanks a lot!!!! Thomas.
http://i121.photobucket.com/albums/o201/Blodfest/sgsystem.jpg
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Bias too low for any of the more common tubes. Amp must be mod-ed. 6ca7 looks like a good one kt90 might be better but more expensive.
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Got these for you. Definately something should have been changed to run el34s.
The 2 8417 tubes put out 100 watts . EL34s probably half that. Have you tried another set of tubes yet? Perhaps the old ones are worn out.
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