1200 sunn head crackling when turned on

[dominicRHIN]

When turning on i hear can crackling. it goes away quickly, if i turn on and off I will not hear it but if it sits for maybe more than a hour i will hear the crackling when i turn it on.....I noticed some flashes of light from the tube on the far light....is that the pre amp tube? do they or one of them need to be replaced.....video attached

 

[Old Garage-Bander]

When turning on i hear can crackling. it goes away quickly, if i turn on and off I will not hear it but if it sits for maybe more than a hour i will hear the crackling when i turn it on.....I noticed some flashes of light from the tube on the far light....is that the pre amp tube? do they or one of them need to be replaced.....video attached

Is the noise coming from the amp only, or do you hear it coming from the speakers?

 

[dominicRHIN]

Is the noise coming from the amp only, or do you hear it coming from the speakers?

i have tried on two different cabs with the same head, noise comes out of speakers as i turn on

 

[SunnBass]

My guess is leaky capacitors, and a tube preparing to fail.

 

[Bill Whitehurst]

I am assuming that this amp has never had anything done to it.
Based on that;
replace filter caps
retension tube sockets
clean pots
then get back to us.

If that dosen't cure the noise, it is still not a waste,
as it should have been done by now, anyway.

 

[Alex O]

I miss having one of these, crackles and all.

 

[Mr. Foxen]

This is the solid state rackmount job, not the old valve power section one. They are notorious for failed solder joints on the pcb that is a giant nutpain to fix, they do this when they have it.

 

[agedhorse]

This is a fairly complicated amp, the output stage is not simple class AB. You may want to find an experienced tech who has a track record with this particular product, or its Fender equivalent. Disregard all the guesses that are trying to be helpful, this is not an amp to attempt fixing based on well intentioned guesses.

Where are you located? Often, an older tech at a Fender Electronics service center can end up being your best bet, otherwise a hack tech could easily turn this amp into a smoldering piece of scrap.