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Post subject: Help!! My Pro Jr with Random Volume Drops!!
Posted: Wed Aug 12, 2009 9:22 pm
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Was playing my Pro Jr and all of a sudden the volume would randomly drop and would fluctuate. Sometimes, it would sound flabby and would have a buzzing noise. This would happen at any volume. I have a pair of JJ el84s and EH 12x7as installed. Any idea what is wrong?

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Posted: Wed Aug 12, 2009 11:02 pm
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Most likely a bad tube or set of tubes. What you should do is go and buy a set of new preamp and power tubes and then, being very careful in the process, replace the old tubes one at a time. After you swap out each tube, fire the amp up and test it; any problems caused by a bad tube will be resolved by its replacement.

On the PJ you will have to take the back of the amp right off. This requires that you carefully unscrew the 5 Phillips-head screws before removing the back panel. While this does expose the amp's guts, do not fiddle around with anything other than the tubes! Valve amps contain lethal voltages in their capacitors that can kill you.


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Posted: Tue Aug 18, 2009 10:27 am
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Ok, I just installed a new set of JJ el84s and a pair of EH 12X7A pre amp tubes, and the problem is still there. The amp is not as loud as it use to be and when I turn the volume above 6, the sound gets buzzy. I would hear some grumble noise and the volume would just randomly get louder and lower. What is going on? Anyone? I always play the amp on the volume 3 settings.

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