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So I have this amp on the bench. Dude says it happened to him at a gig. In his second song, he is playing away and all of a sudden, it started humming VERY loudly with a signal just barely able to be heard through the hum. I had it for 3 days before I was able to get it to happen to me. It sound like when you turn an amp on and you dont have the cable plugged into your guitar and you touch the tip of your 1/4" cable and you can, indeed, hear a very grainy, faint guitar signal going through it. I turned the standby off and back on again and I couldn't get it to mess up again and it has been 2 more days of trying... I checked the power tubes with my tube tester, they tested around 80% but looked like they got REALLY hot as the bases are turning black from a brown color. I retubed it, rebiased it (37mv) and I gave it back to him. Well, it didn't again at his next gig. Any ideas? Oh... all the preamp tubes tested really strong... but I know that doesnt mean much.
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Check your solder joints on the input jacks. Clean the effects loop jacks.
nosajsoldering stuff that's broken, breaking stuff that works, Yeah! -
When it happens, ball up your fist and whack the top of the amp hard. Any change?
Maybe the tubes DID get real hot. When it happens did you look at the tubes to see if they were getting red hot or anything?
For that matter, whack it hard when it is NOT doing it, does that make it start?Education is what you're left with after you have forgotten what you have learned.Comment
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I did check the input for bad solder. I didn't see it but I reflowed it anyway. I also cleaned the input Jack and the effects loop jacks... And Enzo. The time I did get it to start humming, the tubes were definitely not red plating and i tried whacking it on the top to get it to stop. No avail. After I turned the standby off and then on, i tried whacking it again to get it to happen also to no avail... I read somewhere that the crappy wire connecting the input jack board to the main board caused a dude some problems so I hardwired it. I'm still trying to get it to fail. I MAY have fixed it, but I really dont wanna give this guy his amp back again only for it to fail mid gig. Just sayin.Comment
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Have you spun all the knobs . I just got one in needs the Overdrive vol pot replaced something jammed it in . Sometimes it makes connection and sometimes during a gig it crackles and hums.
Customer already identified it so its just a replacement.
nosajsoldering stuff that's broken, breaking stuff that works, Yeah!Comment
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Also,' rock the preamp tubes in a sort of rotating motion in their sockets when the problem happens OR to try and make it occur. This is bad solder joints, dirty contacts or both.
"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." HelmholtzComment
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Thanks Chuck H. I will try that. Actually, I kind of suspected V1 as it has a rubber O-Ring around it. I assume that's to quell microphonics? Does it really need to be there? It just seems like the tube isnt seating all the way, as it looks off somehow...Comment
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Found this problem but I didnt realize it. Lol! This amp has the input jack mounted to a small board with leads attached at both ends to 2 pin plastic, keyed connectors. I went to remove it and it slipped off EXTREMELY easy. So I just clipped the connectors off and hard soldered the wires to the board. That fixed it apparently as I gave the amp back to the customer and he jammed on it for hours with zero problems...Comment
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