Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: greg7vwh on January 20, 2013, 05:43:56 pm
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Hey guys, didn't know who to ask for this amp problem, but found this website and figured a tube amp is a tube amp. Anyway, here is the problem I'm having with my somewhat new amp. When I first power it on everything works fine for a short time, then it looses 99% of power and makes a lot of cracking and popping when I shut it down.. I have replaced all the tubes, including the EL-34's and biased them just a tad cool at 25ma per tube. ( Was told Carvin sets them cold at around around 16-17ma from factory).It worked great for about 20 minutes, then lost power with the same issue it had before.. Any help would be gladly appreciated. Thanks! Greg
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when you say 'somewhat new' exactly what does that mean? are you saying you just got it but it is already having probs? if that was the case then there should be a warranty....but, i'm guessing there is not a warranty or you wouldn't be trying to trouble shoot it yourself, right?
the internet would be my suggestion as the place to start. see if you can find other amp owners with the same amp, having the same problem and there should be a common cause.....
:icon_biggrin:
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Hello Greg,
Give the effects loop jacks a workout with a plug or open it up and check tension - clean and re-tension if needed. Start with the easy stuff first!
Jim
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Thanks guys! I bought the amp about 1 1/2 years ago, but not from Carvin, it worked fine up until just a couple months ago. I am running a boss EQ through the effects loop, maybe the effects loop is where the problem is. I will check into that.. Again thanks! Greg
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Just another something to metion. I didn't see any bit of glow coming from any of my (5) 12AX7 EH pre-amp tubes. And this was when the amp was working fine and before it lost power a little later. I even turned off the lights, couldn't see any glow at all from all 5 tubes.. Any thoughts?? Thanks! Greg
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IF you know how to do so carefully, I would check voltages on your tubes and post those including the heater voltage on V1.
With respect, Tubenit
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I even turned off the lights, couldn't see any glow at all from all 5 tubes..
That's a big clue. While the amp is working, turn off the lights. Can you see a glow form those 5 tubes now?
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Steve, thats what I did yesterday. While amp was up and working I turned off the lights and I still couldn't see any of the 5 tubes glowing at all.. Greg
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And this was when the amp was working fine and before it lost power a little later.
I must have had blinders on when I skipped over that part. Sorry
Voltage readings and a schematic would be very useful.
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Lol thats cool Steve. Adjusting the bias pot I don't mind, but touching other parts in all that electric stuff gives me the shivers.. I might better leave that up to someone that knows what there doing. Anything more simple that I might try first?? Again thanks to all.. Greg
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If you call Carvin, they may have some suggestions.
Like anyone else, they like to see their amps keep working.
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6G6,
I have tried to correspond with Carvin via email, but I haven't had much luck, I didn't buy the 100 watt head from them, but I did buy the new Legacy 2 2 x12 cab to go with it. Guess I might have better luck giving them a call or try and find an amp tech near me ( Palm Coast area). Thanks so much to all, I have got more from this website so far than dealing with Carvin.. Greg