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Post by brendanp on Oct 12, 2018 0:22:49 GMT -7
Just an unusual activity report:
I'd had a bit of an occasional hiss developing, so I knew a tube somewhere was going bad, but two days ago while I was practising at home at bedroom volume my Maz 18 combo suddenly dropped in volume and two seconds later an almighty screeching started - every few seconds the amp would squeal at high frequencies very loudly, in a kind of Nels Cline/Kaoss pad abuse way. Turn off, turn on - same problem.
Yesterday I got around to swapping out tubes to find the problem - I'd never heard an amp do that before. A microphonic tube usually just rings, in my experience, but this was something else entirely. Anyway, started with V1 12AX7 and there was no more screeching, but there was cracking and popping after moving to on from standby and the amp was humming way more than it used to. Swapped the power tubes (which are less than a year old) and all was good - silent amp, back to perfect service.
After so many years, still so much to learn about how problems present themselves.
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Post by zpilot on Oct 12, 2018 7:06:30 GMT -7
You noted they were less than a year old but did not indicate how many actual hours were on them. New tubes can be iffy. I tech for some other players so I have the benefit of learning from them how many hours they average before failure. Then for my personal use I will replace those tubes at about 3/4 that time. It's not worth it to wait until they fail. That last 1/4 of their life they are probably on the downside of performance plus when they fail there is a chance of them damaging another component.
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Post by brendanp on Oct 12, 2018 7:17:36 GMT -7
Good point, zpilot - I play every day, and in previous amps (I bought the Maz last November/December, so that was the first set), with the same play time, my power tubes have gone much longer. Not saying I expect all amps to exert the same pressure on tubes - it's good to have a baseline to work with as a guide for the newly inserted set.
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