Big Block 750 - stuttering noise issue

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warped

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Nov 29, 2006
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Hi,
Last night at Jam our bass players Big Block 750 started stuttering/crackling.
It has had this problem in the past and hasn't really been fixed/properly diagnosed by every amp tech it has been taken to (most are unable to re-produce the problem, others have re-tubed the pre-amp section and said it's all good, only to have it start doing the same thing a few weeks/months later, someone else has said there were metal shavings on the tweeter in the cab which they cleaned and said it was good to go)

It got through the first set no probs, second run through it started (which makes me think it may be heat related).

We swapped all the pre-amp tubes and it still happened (we left it out of it's rack case with the top off, which makes me think twice about thinking it may be heat related)

We swapped cables - had bass plugged straight into the input so it's not an instrument cable issue.

We plugged the DI into the PA and it the sound wasn't coming through the DI'd signal.

Is there anything we can do to troubleshoot the output section of the amp? We are trying to find someone to lend us a cab just incase it's something going on there (I don't think so - I think it's related to the amp heating up and eventually something becoming unstable - maybe a solder joint or something like that, but I don't know how to troubleshoot that kind of stuff).


Cheers guys,
Daz
 
Have the power tubes been changed? try tapping lightly on each powertube with the eraser side of a pencil and see if that makes more crackling/feedback. Maybe dirty tube terminals? Spray contact cleaner on the tube pins and work them around (GENTLY) in their sockets.

That's all I got... Best of luck to you, sir!
 
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