Help with debugging amp...

[shanter]

ok, i dont frequent any other forums about guitar electronics so im going to post this here. i hope thats ok.

i bought a fender deVille 2x12 in december last year and until about a few weeks ago its been an amazing amp. the problem arose out of nowhere and i have no idea what could possibly cause it.

every few minutes/seconds the amp makes a cracking sound mixed with that sound you get when you blow into a microphone. here are the details:

theres no order to it its very random and it comes and  goes at its own will.
the problem persists even with nothing plugged into the input.
the cracking is independant of the master volume.
when i switch to the gain chanel the crackling disappears.

im ready to send it back to fender or get it fixed at a local shop, but i figured i'd run it by you guys before i did anything.

any ideas would be greatly appreciated.

-shant

[Sir H C]

First guess would be tubes.  Preamp tubes getting noisy.

[shanter]

thanks SirHC
that's what i thought in the back of my head, but would they go bad that quickly? or could they have installed faulty tubes??

-shant

[fixr1984]

My father-in-law has the same amp, bought it used a few years ago. About a year ago he had the same problem and it actually led to being non working.
It had to be repaired and it was a resistor that had gone bad. And from what he tells me its starting to do it again. Thats all I know about it but I hope that helps.

[shanter]

Ok, so i did some research on this resistor problem and i read that someone on harmony central had that same problem when he first got his amp too, and then after getting it repaired, everyhting was fine. Apparently it was a filtering resistor that had gone bad.

i guess i gotta call fender, cause i have no clue how to figure out what to change.