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Vintage threads from the first ten years
help w/ Alamo Amp
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 5/31/2000 3:43 AM |
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TC |
help w/ Alamo Amp I'm working on a freinds Alamo Electra. It has low volume output. Without a schematic I tried to track down the problem. Since both channels were equally low volume I assumed it was past the preamps. I tried a new output tranformer, then new power tubes and still low volume. Then I checked the phase inverter tube (a 7199) and found low voltage on one of the plates. I disconnected the plate resistor and found higher voltage on the lose end of the resistor, so I assumed it was a bad 7199. Since the cost of this tube is more than he paid for the amp, I rebuilt the PI circuit for a Fender style 12AX7 PI. Now there's even less output, UNTIL I switch off the amp. Then theres a volume swell that sounds great for a split second, and then it does the same thing if I immediately switch it back on. Great sound that quickly fades out. What should I look for? |
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| 5/31/2000 2:14 PM |
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| TC |
Never mind, I figured it out. There was DCV on the grid of the phase inverter so I added a coupling cap that solved the problem, now the amp sounds great! Thanks TC |
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