Concert Lead with Crackling Noise

[sunngri-la]

Hey gang,
  long time no see.  Good news...my Solarus is working, working, working, and then working some more.  On a sadder note, my father (an extremely dedicated Sunn man) past away earlier this year. I have inherited his Concert Lead.  The latter not being all that sad.  It works and sounds exactly like it should--GREAT.  One small problem I can't get to the bottom of though.  When the power is initially turned on the amp makes a loud crackling sound.  It starts mildly, then become almost unbearable, then after 5-10 minutes of warmup it totally goes away.  I totally cleaned it out...that didn't work.  I checked for bad solder joints, found one, then fixed it...that didn't work either.  The volume control effects how loud the noise is but the treble boost does not.  The noise is present on both the Dist. and Reverb channels.  I am totally stumped.  If anyone has any ideas or suggestions, they would be greatly appreciated.  I really want to get this thing in tip-top shape.  I know my dad would love that.
Thanks guys.

mike

[..tube]

i have 2 ideas. a capacitor is breaking down and leaks it's charge, or you have a bad solder joint or loose socket connection to an output transistor that changes resistance with increasing temperature.

chasing your problem down should keep you off the streets and out of the bars for a while!  

best regards, tube

[sunngri-la]

It'll have to wait until after the holiday.  Happy Turkey-day everyone.  The cap sounds like it's the most likely candidate because it's never been recapped.  I appreciate the reply and I'll keep you posted when I get to look at it.

Thanks again.  
mike

btw nothing will keep me off the streets and out of the bars