New 50 watter, crackling noise when warmed up

[fp2000]

I just finished rebuilding my own variation of non-hrm101. When I first turned it on I freaked out because I could not hear anything, it was completely silent, until I plugged my guitar in and there was beautiful 3d sound, but after a little while I can hear crackling noise when not playing. Kind of like the noise of an old lp record, it is not too loud but could anyone here tell me what that is. First time this happens to me. I suspect a cold solder joint. My circuit board remained in my garage all winter unsoldered and I noticed the eyelets turned dull. I imagine the humidity could have caused that.
I just wanted to confirm. I does it with different tubes, however 6v6's were the quietest.
Also, I noticed that I can get 440v on the plates of 6L6 tubes, but only about 428v on 5881's. I use tung-sols reissues.
I appreciate any guidance on this.
Thanks

[talbany]

Start pulling preamp tubes..V1 first V2 and PI..If it stops replace the tube..If it still makes noise you've isolated the section where the noise is coming from..Double check all grounds solder joints etc in that section..That's first..Report back if you get confused..
Good Luck

Tony

[fp2000]

Thanks Tony. Also, is it normal for the voltage to drop more than 10volts just by using 5881's vs 6L6's?

[talbany]

Voltage drop where?

Tony

[fp2000]

the plates

[talbany]

First off most 5881's can't handle 460 (360 max plate voltage)...Pull the spec sheets check the voltage ratings and cross both tubes current draw..5881's spec's can be all over the place..(I've put 700v on Solvtek 5881's)

Were the 81's crackel-ing? (Arcing) you may have fried them!

Tony

[fp2000]

the tubes are fine, they are rated for 400v. Right now they got 428v on the plates.
The question is, does anyone know if the voltage is supposed to drop from 440 to 428 by changing from 6L6 to 5881's?