Georgia Blues
167 posts
Aug 31, 2015
5:56 PM
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OK, finished a gig where I pushed my Blues Jr. pretty hard. Come back to my studio and plug in and I have decidedly less power coming from the amp. Max volumes that used to be 5 and 6 are now 8 and 10. What's up? any suggestions for where to hunt?
Last Edited by Georgia Blues on Aug 31, 2015 5:56 PM
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nacoran
8647 posts
Aug 31, 2015
7:24 PM
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One of the tech guys will probably have a better idea, but depending on your age you may want to get your hearing checked!
Only half kidding. Ear fatigue can be pretty pronounced. By the end of the night at a loud show I'll have markedly less hearing than when I started, and it can last for a couple days if I haven't used ear protection, and what are you comparing it against? If there are other amps in the mix rule out the obvious like the other guys turning up. Sometimes guitar players don't even consciously notice that they are doing it. It can take catching them in the act and pointing it out for them to realize it. That's always the first thing I look at. You'd also be surprised how much how you have it EQ'd can change the overall volume. Assuming you've got the simple things checked though, one of the tech guys may have more useful info for you.
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Nate
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5F6H
1887 posts
Sep 01, 2015
3:06 AM
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Assuming that the amp used to feedback at 5-6 and now doesn't until 8-10, with same mic & settings (note fat switch position etc.), it looks like something has failed.
1st stop is to sub preamp tubes with same type in the same position to rule out a tube failure.
2nd stop - if you have bias probes/known good power tubes that have previously worked in the amp - try subbing the power tubes. Ideally, power tube bias should be checked/confirmed when subbing in this amp.
If the loss is still evident then it needs checking by a tech, a dc voltage check & OT winding check may reveal something like a burned plate resistor?
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Georgia Blues
168 posts
Sep 01, 2015
5:42 AM
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Thanks 5F! Now I'm depressed, but have an idea what to do.
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Barley Nectar
905 posts
Sep 01, 2015
3:27 PM
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A bad bypass cap will do that also. Amp will sound about the same, just less loud...BN
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Georgia Blues
169 posts
Sep 03, 2015
6:40 AM
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OK, I swapped out the preamp tubes and I'm back! vintage AV 7's in 1 and 2 and a long plate DW7 in three. Thanks for your help guys.
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Barley Nectar
907 posts
Sep 03, 2015
8:11 AM
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I'll bet only one of those tubes was the problem. Try an test then , one at a time, in the amp. V1 position is the best place to do this as that socket is first in the gain chain, except that DW7 which you were probably using as a phase inverter. Test that one in it's correct socket. Many good tubes get tossed because folks swap out all at once. Those "still good" tubes may work for years to come...BN
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Georgia Blues
170 posts
Sep 03, 2015
3:50 PM
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Barley! I expect your suggestion is on the money. I have saved them all and was considering a test pattern just like that. What I was not looking forward to was dropping my amp of at a shop.
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