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Posted: Fri Apr 04, 2008 2:09 pm
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I would still look for the loose connection thing as well. Because it is a combo amp ... when you crank up the volume you could be getting microphonics, meaning cabinet vibration might be causing the crackle. This is VERY common, but usually affects tubes most often. You can rap the cabinet with your fist, not too aggressively, to see if you can get a response ... or tap the tubes, lightly with something not metallic (I flick my finger at them, nail side out) and see if you get a response.

Broken record time ... before changing caps and tube sockets the amp was good ... now it isn't. Start there!!! If you are absotively posilutely sure that ain't it, then look at what the change might have affected. Slightly higher voltage (less leakage on the filter caps, although readings seem very nominal, not even above middle-high) more surge through the transformer and diodes, (better cap performance, quicker charge rate). I would then just start swapping tubes ... but then again, I have spares. But with the concert that is still pretty easy ... the 12ax7s are the same as the 7025s. Keep a log of what you are doing and pull those out of the tremolo circuit and put them in other places ... one at a time. If it isn't a connection ... which I would bet lunch on, then it is probably a power tube arcing (from the description of the sound. Been there a few times.) Pots ... maybe, but moving them from one position to another a few time usually stops any noise you notice while not touching them.

Haven't hear much from the Admiral since he was taking HV readings. Hope he hasn't hurt himself! :(


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Posted: Mon Apr 07, 2008 10:56 am
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Ah, the forum's open. Problems fixed. Thanks for all your input guys. 8)


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Posted: Mon Apr 07, 2008 11:00 am
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Ah great Admiral ...

But, you gotta share ... what was it? I am sure we are all dying to know!

8)


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Posted: Mon Apr 07, 2008 11:09 am
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It was another plate resistor coming off of V1b. It tested good but it was arcing internally.

Recap: 2 new powertube sockets, new powersupply capacitors, 2 plate resistors, everything sprayed\cleaned and 3 coupling caps. Good as new!

She sure sounds sweet now. Thanks again. :)


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