Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Paramount => Topic started by: thdewitt on October 27, 2014, 08:36:11 AM
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OK, so I built both 2 Paramounts. The first all the voltage and resistance checked out fine. I adjusted the trimmer pot and hum balance and it sounds great. The other side has the same voltages and resistance but I am getting no sound. Any thoughts?
Thanks,
Tom DeWitt
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It'll be something simple, like solder shorting the RCA jack, a wiring error on the output transformer, or the grid resistor on the output tube being soldered to the center lug of the terminal strip.
If it's none of those, you can download a 60Hz tone to play into the amplifier, and we can use your meter set on AC volts to trace the signal through the amp.
-PB
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Well, I just tried to go straight form th phono stage to the amp. I get very faint music. Still looking for the cause.
Tom
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OK, I tested the RCA and it is not shorted. I checked the output transformer wiring twice and it looks fine. Not sure what you mean by the grid resistor on the output tube being sobered to the center lug on the terminal trip. I checked all the pins on the 9 pin and they seem to be right.
Tom
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So.... I am getting music at the speaker outputs but it is very faint. Not being amplified???? What would that mean.
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The next step is to take PB's advice to put a signal into the amp and trace it. You can check it at the center pin of the RCA, then measure AC voltage right at pin 3 of the 5670. If they aren't the same maybe the 220 ohm grid stopper resistor at pin 3 is damaged.
If they are the same, measure AC voltage at pin 3 of the big tube. It should be a lot bigger because the first tube will have amplified it. If it is not, once again make sure the 220 ohm grid stopper resistor at the pin is good. If signal is good all the way to that point, measure it at output transformer OT-1 terminal 7. Again, it should be a much higher voltage. If you don't see signal there check your output cap connections. If signal is good there, go over your output transformer secondary wiring and the binding posts.
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OK, I set up my function generator for a 60HZ signal and connected it to the RCA inputs the used my oscilloscope to take the measurements.
Voltage
at RCA 2.2 Vpp
at B3 2.2 Vpp
at A3 64.4V Vpp
at OT-1 Terminal 7 15.1 Vpp
Good Paramount
at RCA Jack 2.22 vpp
at B3 2.22 vpp
at A3 55.2 vpp
at OT-1 Terminal 7 12.9 vpp
I still can't tell where the problem is.
Thanks,
Tom DeWitt
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More readings
242 VPP from terminal 6 of the Output capacitor.
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OK. I don't know what happened, but something must have knocked loose, because now everything works fine. Go figure. Thanks for the help. problem solved and music playing. Very nice with Eros and Paramounts. I have a submissive now but waiting for Bee Pree to arrive.
Tom
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Probably one of those deals where you flipped the amp over a couple times in testing and some hidden bit of cutoff wire that was shorting something fell out. Tne guys here always pick an amp up and shake it a bit after working on it to make sure nothing stays in there that shouldn't