Amp crackling

[mr.L.]

Some might have seen this in the mesa caliber .50+ thread, but I thought I make a separate thread for this as it might be useful for other people with similar problems as well (and draw extra attention of course ).

So I bought a Mesa Caliber .50+ and it has some strange hissy/crackly noise (sounds like playing an old vinyl record). It's pretty low level and doesn't seem to be effected by the volume of the amp, but it's annoying nonetheless. I've recorded a small bit of it:

http://www.box.net/shared/quj91i7tkd

The odd thing is that it is not always there (especially in the first 10-15 minutes after powering it up) and does not seem to be effected by the control settings or channel settings or whether or not a guitar is connected.

So far I've cleaned out the input, footswitch and cabinet jacks by putting a cable in and out a couple of times and using a bit of contact cleaner as well as some compressed air. I've opened up the amp and used compressed air to blow out any dust and turned the pots a couple of times and blown these out as well. No luck so far

Does anyone have a clue what the source of this problem might be?

 

[mr.L.]

Did some additional testing. The problem seems to be in the power amp section. When I connect another preamp through the fx return I run in to the same problem after a while. However if I record the preamp section the crackling is not there. So could this be a faulty power amp tube?

 

[Metaltastic]

Hmm, good call on testing each section separately, and yeah, in my (admittedly somewhat limited) knowledge of the workings of amps I'd guess a power tube would be at fault - honestly, whenever buying a used amp, I think it's a good idea to just swap in a new quad (or pair, if it's 50 watts) of power tubes for a clean start! And a new balanced 12AX7 for the Phase Inverter as well.

 

[AudioPhile777]

Yeah, my amp is starting to do this... I'm looking into new power/pre tubes at the moment...

 

[mr.L.]

Hmm, good call on testing each section separately, and yeah, in my (admittedly somewhat limited) knowledge of the workings of amps I'd guess a power tube would be at fault - honestly, whenever buying a used amp, I think it's a good idea to just swap in a new quad (or pair, if it's 50 watts) of power tubes for a clean start! And a new balanced 12AX7 for the Phase Inverter as well.

Yeah I cursed myself for not thinking about this earlier hehe. But now at least it's become a bit more clear were the problem is located. I didn't change the tubes because the guy I bought the amp from said they had been changed not too long ago and the amp hadn't been played much since. I got in contact with him and he is going to contact the technician who last serviced the amp to see what he thinks might be the problem. He should get back to me tomorrow.

 

[AudioPhile777]

Yeah I cursed myself for not thinking about this earlier hehe. But now at least it's become a bit more clear were the problem is located. I didn't change the tubes because the guy I bought the amp from said they had been changed not too long ago and the amp hadn't been played much since. I got in contact with him and he is going to contact the technician who last serviced the amp to see what he thinks might be the problem. He should get back to me tomorrow.

unless he's a friend of yours... take everything he said about the amp and throw it out the window... always check it out for yourself... let the thing sit there in standby for 10-15 minutes, then play it for 10-15 minutes and then leave it on without playing through it for 10-15 minutes... if the seller isn't willing to let you do this, then there is something wrong with the amp...

 

[mr.L.]

Thanks for the advice. I did check it out but in the time I played it there was only crackle when turning the pots. So I thought just some scratchy pots nothing to worry about. Next time I'll check if there are any noises without playing it. Guess I've been lucky with buying second hand gear sofar that I don't really expect things to be out of order. Since I got the amp pretty cheap, even if I'll end up paying for some servicing it would still be a good deal. So hopefully it's nothing too serious and I can work out a deal with the seller.

 

[Wolfeman]

Could be a failing cap also. I wouldn't go that far though until you have swapped tubes.

 

[mr.L.]

Yeah I've been doing some reading and came across that possibility as well. Might run it by a tech just to be sure.