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Anybody have experience repairing amps?

My head blew in the middle of practice last night (10 days before a gig!). It's a Line 6 Duoverb head. I was on a clean channel, and brought the gains up to increase the level on that channel. I must have driven them too far up. I hit a chord, and the amp went into something that sounded like delay- DAT! DAT! DAT! DAT! I tried to kill the master volume, and it had no effect. I shut it off. It was really hot in the back! I waited for it to cool off, and tried to power it up again. No lights, no signal, but a rhythmic (but quieter) tick tick tick tick through the speaker. I disconnected it, and took the head home. After a few hours, I tried it again. I could hear the tick tick inside the amp, even with no speaker connected. Could this be a capacitor that blew? Is the ticking sound the cap trying to ramp up?
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Re: Anybody have experience repairing amps?

11/26/2008 4:26 PM

Nick Scratch (438) wrote:

That's the sound of your amp telling you to take it to a good tech.
There's nothing in there that you can fix on your own, especially if
you can't diagnose it on your own.

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Re: Anybody have experience repairing amps?

11/26/2008 8:38 PM

Dave Magaro (1726) wrote:

Never heard one tick before. Your best bet is to take it to someone if you don't have at least some experience with electronics. If you do, one thing you could try is: if you have a line out (I'm not familar with the amp) you can run out of that into something. If that signal is fine then chances are it's in the output section. I just fixed both of my heads. I swore my Sunn was blown output transisters, but it turned out to just be solder joints. Yours ticking makes me think it MAY be in a protect mode. If that's the case it's probably in the output section. Sometimes you can see the bad components with a visual inspection... a burnt resistor a swollen cap, etc. But, even if you find one of these there could be something else bad that took that component out. I know one time I was fixing an old CS-800 power amp. I went right for the output transistors and found a blown one. I replaced it and plugged it back in. A few seconds later it burned a hole in the top of the transistor and was shooting sparks about 3-4 feet in the air....LOL! Obviosly there was a problem before the trasistor. I went through it and found the other bad components. But, you want to talk about one tenative man plugging in a power amp!

Dave

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Re: Anybody have experience repairing amps?

11/30/2008 7:15 PM

Michael Laurance (4040) wrote:

I try to do some of my own repairs before having to take it to a tech, but this one sounds like I might not have a choice. I was just hoping that someone on here was an amp tech.

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Re: Anybody have experience repairing amps?

12/4/2008 6:42 PM

Dave Magaro (1726) wrote:

If you run out of your line out into another amp and it sounds fine you will know that your preamp section is good. Normally a ticking in electronic circuits indicates that it is in a protect mode. Either an over voltage situation, or a short. The circuit will continue to try to restart. I don't know if that's the case here, but I've heard that kind of ticking in other circuits. I couldn't find a schematic for this head, but I'm assuming it is solid state? If you test the preamp section and that's good the next logical step is the output section. The first thing I always test are the output transistors. That is the most common thing to fail considering the stress they are under. And it sounds to me like you may have pushed it a little too hard. If you have a multi meter, and know how to test transistors then you can find out quickly if one is bad. Electrolytic capacitors don't tick. They may hiss, but in the hundreds of thousands that I've dealt with I have never heard one tick.

Contact the manufacture and talk to a tech. They should be able to at least tell you what the ticking sound is. I'm sure you're not the first one that this has happened to.

Best of luck with it. I hope you get it straightened out.

Dave

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Re: Anybody have experience repairing amps?

12/5/2008 1:51 PM

Michael Laurance (4040) wrote:

Wow, thanks for the info! I think that it might be in the pre stage, because I'm getting anything from the line outs. I'm also not getting any lights, so I agree that it's likely in a protect mode. Hopefully I can get it opened up this weekend and see what I can find on the meter. Is it possible that there would be a reset inside? Is it possible that there's a fuse like in a tube amp?

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Re: Anybody have experience repairing amps?

12/5/2008 2:01 PM

Dave Magaro (1726) wrote:

Hey Michael, I was looking for a schematic for your head and stumbled across online tech support for Line 6. Here's a link for you:

Line 6 Tech Support

They will be able to tell you far more than I can.

Dave

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Re: Anybody have experience repairing amps?

12/8/2008 8:45 AM

Michael Laurance (4040) wrote:

Thank you! I'll hit them up today.

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Re: Anybody have experience repairing amps?

9/24/2009 1:42 PM

Jyme Bale (2) wrote:

If you do not have any electronic experience with amps do not mess with it. I've seen people get knocked on their butt trying to pull a part out with the power cord disconnected. Take the amp to a tech period. I toured as a pro keyboardist/vocalist for 35 years and had to stop because of three very bad car accidents. They messed my back up real bad, so I know of what I am saying.
cheers

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Re: Anybody have experience repairing amps?

11/10/2009 11:14 AM

Don Molenda (6) wrote:

currently working on the same head.the ticking is the pwr sup
brd cycling up and down. this amp has NO output protection!
uses a pair of TAD7293 100 watt amp chips($8 ea @ BDENT.om)
open the unit careful of the short leads to the on/off swtch.
unplug the cables(squeeze to release) (3) from the amp section
.then plug it in and see if it pws up if it does ..then you blew one
or both of the pwr chips(the ones braced against the heat sink).
see the note on the pwrsup brd** do not operate without being
connected to a PROPER load*** that means ...verify with an
ohmeter that your cabinet ACTUALLY IS what it is !! 4x12s can
be 4-16 ohm s and if some moron just put NEW spkrs in it
..cause they were laying around...who nknows if the cabinet is
wired correctly??... oh yeah the owner of the head pays the price!
remember ..theres' no output on this $1000 head..GOLLY!! you
know what i actually said ..right!??
ps: the amp REALLY is high tech and assenmbled well!! SMT
technology

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Re: Anybody have experience repairing amps?

11/10/2009 6:26 PM

Charles Ross, Jr (538) wrote:

hey don,whats up? i use to work on amps off and on my question is have you installed heatseeking to asorb?(spelling sucks lol) and those smt sucks lol