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I am new to forum. I have an old supro(valco) amp 5y3-6v6-when I got it the amp worked great. I tried it the other day and the amps volume has become real weak and seems to increase slightly in middle position then fade on full volume.I have tried different tubes to no avail. any ideas would help. thanks RC
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Is that the one with three tubes? Like 12AX7 as well as the 6V6 & 5Y3? If the amp is original it likely needs some new coupling caps, and electrolytic filter caps. Does it hum very much? Of course it could be other things as well.
There is also an older version with a 6SL7 rather than the 12AX7.
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The amp does not hum. yes it is a three tub amp. rcComment
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OK Rick
Is it original enough to have the old caps in it yet? Like I mentioned, the fix may be to replace the old coupling caps. If the power transformer is quite warm or hot, it may have a filter cap leaking enough to pull the high voltage down, making the volume low (been there).
The fuse should be 2 amp, according to the schematics. Make sure it isn't any larger rating.
The pre-amp tube should be a 6SL7 if it's a 1947 etc vintage, and a 12AX7 if it's a later version.
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Welcome to the Forum and hope this is a minor repair but these symptoms are sounding like a possible bad Output tranny. Do you have a multimeter you could use to ohm it out ? Could be a bad connection,tube socket or even a preamp tube.KBComment
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That's right, what KB said. Also you could check for the voltage on pin 3 of the 6V6 to see what the plate volts may be. Not sure what would be normal, but around 260 or so sounds like the B+ voltage may be OK. You really need a multi-meter to pursue the problem.
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