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Old 27th April 2005, 10:07 PM   #1
Optical is offline Optical  New Zealand
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Join Date: Nov 2002
Location: Auckland, New Zealand
Default Tube amp volume fluctuation

I have a tube preamp and amplifier and the volume will suddenly drop or violently increase..

I have recently changed all the tubes in it so i dont think they were the cause..
Its possibly a faulty component somewhere would you think? none of the pots are scratchy..

could it possibly be the output transformer? the amp does this when hot or cold though..

i just dont know
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Old 28th April 2005, 03:40 AM   #2
Enzo is offline Enzo  United States
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Join Date: Sep 2004
Location: Lansing, Michigan
Could be cracked solder to a pot though. Is this for guitar? If so, I always suspect effects loop jacks first. To test for that, take a spare guitar cord and plug it into the effects send, and the other end right back into the effects return. If this restores the sound, the retrun jack needs service.

If nothing else, use the two sections with other gear to see which is guilty.
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Old 28th April 2005, 05:05 AM   #3
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Join Date: Oct 2004
Location: Adelaide South Oz
I had this happen to me on a Ampeg SVT Guitar Amp - found a coupling capacitor (input to the driver stage) which fell in half when I prodded it with an INSULATED screw driver. Also could be a dry solder joint. Tap components to see if you can localise the problem and then a good visual inspection will usually reveal the faulty component or solder joint.
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Old 28th April 2005, 09:33 PM   #4
Optical is offline Optical  New Zealand
diyAudio Member
Join Date: Nov 2002
Location: Auckland, New Zealand
Hmm, cracked solder joint eh?
yes it is for a guitar amp! it has no send or return on it through..
it is a really old amp, so perhaps resoldering all the joints and replacing some coupling caps would be a good idea anyway?
thanks for your advice
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