DS>Hello Lee (if I may be so bold as to call you that :-)
That'll do until you respect me enuf to call me Mr. MacMillan.
DS>I have a question.  I have a Randall Pro-Tube 1000  head (55 watts, 5 12
DS>ax-7's and 2 6Ll6's) with a slight problem.  After it heats up, it cuts 
out,
DS>ie there is no sound at all unless I flip it into standby and then back up 
t
DS>full on.  I am inclined to think that it is a capacitor that has dried up, 
b
DS>I am not sure.  It has only started doing this after I replaced the 6L6's.
DS>replaced them with some Groove tubes from woodwind/brasswind, and they 
eem
DS>be working fine.  The only reason that I mention this is because there is 
no
DS>Bias adjust screw on the Randall (maybe they took a Mesa-Boogie approach 
o
DS>amp building), so I am not sure how correctly they are biased.  They don't
DS>seem to run too hot or too cool, but I wasn't sure if this would have 
anythi
DS>to do with the problem I am having now.
You ought to address the same question to Rich Lockyer, he's a better
troubleshooter than I am.  Intermittant problems are the hardest to
find.  Did you try putting the old tubes back in to see if it's tube
related?  Does it cut out while you are playing, and if so, will it cut
back in if you just stop playing for a few seconds (I'm wondering about
a parasitic oscillation)?  I hear the tech at Woodwind is pretty good,
that might be the best bet.  I assume it's not new enough to be covered
under the warranty.  Could be as simple as a cold solder joint.
DS>Also, is there some way to adjust the bias on Randall amps that I just 
don't
DS>know about?  If not, where can I get Randall tubes?
I'm not familiar with Randall amps.  I'll assume if you don't see a bias
pot anywhere that you can't bias them without swapping some resistors.
I wouldn't worry about it unless the power tubes are glowing cherry red
in which case they are probably already fried.  It's probably biased
cold for longer tube life anyway.
DS>Thanks for your time :-)
No problem.  Sorry I couldn't be of more help.
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