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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Vintage R12R Ampeg - guitar amplifier - lack of audio output gain - need help
I have a vintage amplifier Ampeg R12R reverberocket '62s. There are 2
X 6SL6, 2 X 6SN7, 2X 6V6 and 1X 5Y3GT. I would like to know what is the power output of this amplifier? Not the reissue ... I mean the vintage ... I know that the R12R reissue is a 50 W RMS and use others vacuum tubes ( 6L6 instead of 6V6 and 3 X 12AX7). Here is my problem. There is a lack of audio power at the output . The volume position between 1 to 5 is very week (weak audio output) . From 5To 10 (the maximun) the output is strong (guitar control at max) and clean.I think that I have a lack of audio gain at the output of my amp. I checked the bias resistor of cathodes 6V6 (275 ohms on my meter) and I replaced the cathode bias capacitor by a 50 uf 50 V located to the cathode of the 2x 6V6 output tubes.The problem is always similar. I'm quite sure that I have a lack of audio power at the output. I checked all voltages ... it seems all OK. I tested the 2 audio output tubes with a Hickok 600A and I read 4000 mho for the 2 X 6V6 ... OK. The 6SL7 read normal. The 2 X 6SN7 read about 1700 mho the normal value is 2600 mho). I checked all the solders joint and I resolder each eyelets. Many coupling capacitors have been replaced in the section V1, V2, and V3 with very good caps.I checked all power supply caps = OK. The 2 x 6V6 run a bit hot. There is no Hum or strange noise. My problem is ... I have the feeling that ... my output have lack of power. Is it normal with the vintage R12R? If not, what is the problem? Help me a bit. Thanks a lot! Mike |
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Vintage R12R Ampeg - guitar amplifier - lack of audio output gain - n
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