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my trace is poorly


ZPQ
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Hi,
I plugged in my old GP11 4x10 trace combo this afternoon and it's developed a problem.

90% of he volume has gone and it sounds very distorted.

I had a quick look and without doing a full on diagnosis I suspect it's the power transistors that are failing.


Anyone had a similar problem or have any thoughts.


Thanks
John

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Dunno wot you mean, mate. I just prop up the bar and try not to get in anyone's way.

As for the Trace Combo: I'm a valve man meself, but if I can be of any help on the ideas front....

ZPQ: Sorry for stating the bleedin' obvious, but on this amp, is there any way of intercepting the signal path as it passes from the pre-amp to the power stage? If so, you could take a feed off the pre and check if it sounds clean, and maybe feed a line-level signal into the power amp and see what that sounds like.

Next blindingly trite observation: it's not the old "dead batteries in my active bass/effects unit" scenario, by any chance?

Anyone else got any bright ideas?

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is there any way of intercepting the signal path as it passes from the pre-amp to the power stage?

Sounds like a good place to start,try cleaning all the send and return FX loop jacks, especially the shorting contacts which will require removing the amp from the cab(make sure its unplugged).Also worth cleaning the master vol pot.Sounds unlikely to be the power transistors as they usually go dead short when they blow and then take out the power supply fuses.
If none of these work then best to take it to a proper techie.
Good luck
Cheers Just

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Thanks for the replies,

Just had another look at it.

Cleaned the pots and sockets - no change.
Lots of brown gunk inside it - yuck.

Connecting the send and return makes no difference, but there is a line in and connecting the send to this and it seems to work.
Can't crank it up at this time of night, but it suggests that the fault is in the preamp and somewhere around output gain and end of the preamp chain (line in appear to after this in the chain - which I think is a bit odd).

Thanks
John

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Hi Mick,

My last test connecting the send and line in worked fine so I think the speakers are ok, something in the preamp at the end of the signal chain I think.

If I can find a schematic then I think it'll be an easy fix.

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