Crackling amp - can anyone experienced tell what the possible cause might be? (video included)

ryanverbena

I was playing earlier today and my amp started making a crackling sound. It only came up intermittently, and really fizzed out when I switched it off at the end of the clip. Wondering if anyone with experience could tell what the cause might be by the nature of the interference?

(Excuse the playing, was trying to cause the crackle to start and then dampen my strings so it could be heard clearly). 

Jetfire

May help to say what amp it is

ryanverbena

Apologies - it's a Divided by 13 JJN50/100. 

I've just tried switching out all of the preamp section and narrowed down that it's not that. Next is to try the power tubes but problem is that it will need to be done professionally as I'm not sure how to re-bias it once installed (and a quad of el34's aren't cheap). 

ICBM

You don't need to bias it to test if it's a valve fault.

Remove two of the power valves - outer or inner pair. Don't worry about impedance re-setting for this test either. If it still does it, put those back and take out the other two. If it stops doing it, the faulty valve is out of the amp - if so, put *one* of the valves back. That way you can find out if it's a power valve, and which one, before you need to buy more valves.

If none of that stops it, and swapping all the preamp valves didn't either, then it isn't a valve fault and you need a tech anyway.

57Deluxe

Try cleaning the valve sockets

Devil#20

Just pulling the valves out and putting them back in is sometimes enough to sort it out. 

ryanverbena

Thank you all - I think it was some dust in the valve socket because after swapping them around and using a little contact cleaner the problem has gone. 

Wisdom to all!