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I have an early 70's PANaramic 2x7591 based amp that I've been working on on and off for a while now. I picked it up for peanuts in unworking condition, being told all it needed was power tubes. This of course was not true, as when I opened the chassis up I discovered that someone had tried to repair/mod/destroy it and had given up halfway through. No schematic exists, or so it seems. It appears to be the same amp as the Grand Prix, made by Audio Guild also, as well as various other 2x7591 based amps made by Audio Guild but sold under names like Titano, Universal, etc etc. They are related to Magnatone, somehow, and in some ways it seems...The closest schematic I've found is here:
http://f1.grp.yahoofs.com/v1/kDwFTIH...rsatonejpg.jpg
It is not dead on (mine also has reverb and tremolo), but it is SOMEthing.
So both transformers had been replaced, the OT with a fender princeton OT, and the PT with a TP-25 from Allen. Being that it appears the original was not center tapped (nor had the previous owner/hacker hooked it up), I fixed that and also completely redid the bias supply and all power filtering. Sounds OK now, but it is not very loud, and it could sound a lot better. Upon looking at it again today, I discovered that there is 440 volts on the plates. While this might be OK for some NOS 7591's, I am doubtful that the JJ's in it will handle it for very long.
But my main question/concern is the fact that the PT which is rated 310-0-310 is giving me over 350v AC and once through the rectifier it's up to 440v loaded (and 475 with the power tubes pulled). Should I susspect the tranny, or should I just put a big ass dropping resistor before the first filter and get it as low as I can?
I will probably have a few more questions about this guy as time progresses, but I'll leave it there for now. Thanks a lot for the help, as always....
http://f1.grp.yahoofs.com/v1/kDwFTIH...rsatonejpg.jpg
It is not dead on (mine also has reverb and tremolo), but it is SOMEthing.
So both transformers had been replaced, the OT with a fender princeton OT, and the PT with a TP-25 from Allen. Being that it appears the original was not center tapped (nor had the previous owner/hacker hooked it up), I fixed that and also completely redid the bias supply and all power filtering. Sounds OK now, but it is not very loud, and it could sound a lot better. Upon looking at it again today, I discovered that there is 440 volts on the plates. While this might be OK for some NOS 7591's, I am doubtful that the JJ's in it will handle it for very long.
But my main question/concern is the fact that the PT which is rated 310-0-310 is giving me over 350v AC and once through the rectifier it's up to 440v loaded (and 475 with the power tubes pulled). Should I susspect the tranny, or should I just put a big ass dropping resistor before the first filter and get it as low as I can?
I will probably have a few more questions about this guy as time progresses, but I'll leave it there for now. Thanks a lot for the help, as always....