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Rob5246

HD100 MkII head (w/ 412cab) massive buzzing + volume increase. HELP!!!

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I brought a Valve HD100 MkII head with matching cab from GAK in England a couple of months ago now. It started off fine when I was just getting used to using the amp.

 

As I brought it to practise with my band, half way through playing almost all guitar input was drowned out by an intense buzzing / static sound. Ever since then it's been slowly getting worse to the point where it's completely unplayable, I just can't use the amp. The second I turn it on, I hear a faint humming starting up (that shoudln't be there with the standby switch off!) then as I hit the standby, it's instantly doing the huge whirring sound again. 

Sometimes however I can just turn it off and on a few times, and it calms down, and I can just about get away with using the amp... except then the volume pretty much doubles all by itself, and keeps jumping up and down abruptly then the buzzing starts again. 

If anyone has experienced this before, or knows what to do to fix this, please let me know! I have no experience with valve amps, and I've put off fixing it for way too long! PLEASE HELP!

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I brought a Valve HD100 MkII head with matching cab from GAK in England a couple of months ago now. It started off fine when I was just getting used to using the amp.

 

As I brought it to practise with my band, half way through playing almost all guitar input was drowned out by an intense buzzing / static sound. Ever since then it's been slowly getting worse to the point where it's completely unplayable, I just can't use the amp. The second I turn it on, I hear a faint humming starting up (that shoudln't be there with the standby switch off!) then as I hit the standby, it's instantly doing the huge whirring sound again. 

 

Sometimes however I can just turn it off and on a few times, and it calms down, and I can just about get away with using the amp... except then the volume pretty much doubles all by itself, and keeps jumping up and down abruptly then the buzzing starts again. 

If anyone has experienced this before, or knows what to do to fix this, please let me know! I have no experience with valve amps, and I've put off fixing it for way too long! PLEASE HELP!

That's the problem with tube amps, they need to be serviced. I've had an awesome early 1970's Ampeg amp for a long time and it's always taken the abuse I've dished out but when I started plugging in a BOSS GT-10 into it it didn't like that. The BOSS throws out some weird high pitched oscillation thing that I'm sure blew the power tubes. One day whilst hammering out tunes quite loud there was a pop and the Ampeg started screaming to high heaven.

 

I quickly shut it off and within a few days bought a matching pair of 6L6GC's for it and all was well. That's just the nature of the beast with tube amps. Take it into a pro and get it tuned up. The bias needs to be set properly on these SpiderValves as well.

 

One last thing, no matter which tube amp I'm playing through (have many) I always let them warm up for a bit before playing/hammering on them and let them cool down for a few minutes as well after a raucous session.

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remove the inner pair of power tubes, then try.   if it still does it, put them back, then remove the outter tubes.  If you have a bad tube, this test will find it.  My HD100 had an arcing tube, which happened to be in the inner pair.   swapped them both, works great.

 

--edfardos

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I had a problem playing live and at rehearsals , volume shoots up and loss of master volume noisy from hell . I gentally tap the head box and volume shoots down back to normal, ( my head is in a "live in" road case) I changed power tubes and preamp tubes rebiased to spec. I have the same problem volume shoots up loud hiss master volume loss

took the amp out of  box again , put in on my bench checked biasing all good, I tapped the circuit board and the master volume connector was kind of loose i pushed it back on , checked my biasing and removed "front plaxi LINE 6 LED LOGO" to give amp more air she was running hot , bammmmmmmmmmmmmm!!!!!!!!!!!! no issues played the Casino last week amp kicked lollipop, I think this amp needs ventalation or a fan. I did submit a line 6 ticket but I thought Im not spending more cash on repairs,hope this can help my fellow players cheers.  ( I still run amp all day in my studio running hot , still no issues)

regards.

update :2 weeks later.... all good still not issues played live keeping my fingers crossed ...success !!!!!!!!

                                       soundman at bar gave compliments on my guitar tones.

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I've mentioned here before about buying a plastic Marshall vent grill and installing it directly over the power tubes. I think it's the 17 inch one. Mesaure twice, cut once :P

 

I haven't done it yet myself as I don't use my SV HD 100 mkii all that much so haven't really bothered. But I figured a steady hand and a jigsaw and the modification could be done in under 20 minutes and probably make the rare DSP chip and the rest of the amp last many more years.

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