RL>Hello Doug!
RL>On 03 Feb 98, Doug Southworth wrote to Lee Macmillan:
RL> DS> I have a question.  I have a Randall Pro-Tube 1000  head (55 watts, 5 
1
RL> DS> ax-7's and 2 6Ll6's) with a slight problem.  After it heats up, it 
cuts
RL> DS> out, ie there is no sound at all unless I flip it into standby and 
then
RL> DS> back up to full on.  I am inclined to think that it is a capacitor 
that
RL> DS> has dried up, but I am not sure.
RL>Doesn't sound like it.  That'll usually cause humming.
That's true, and I had to ask :-)
RL> DS> It has only started doing this after
RL> DS> I replaced the 6L6's.  I replaced them with some Groove tubes
RL> DS> from woodwind/brasswind, and they seem to be working fine.
RL>Again, I'd put the original tubes back in first... if the problem still 
exis
RL>(and I'm betting it won't), then attack the sockets.
Well, the only problem is that one of the old tubes shattered, so no I
don't have the old ones...
RL> DS> The only
RL> DS> reason that I mention this is because there is no Bias adjust screw 
n
RL> DS> the Randall (maybe they took a Mesa-Boogie approach to
RL> DS> amp building), so I am not sure how correctly they are biased.
RL>It may also be cathode biased.  Cathode biased amps are, to a great 
egree,
RL>self biasing and you really don't have to worry about them.
I don't believe that it is, but since Washburn has been reluctant to
give me any info on the amp, it is a possibility.
RL> DS> They don't seem to run too hot or
RL> DS> too cool, but I wasn't sure if this would have anything to do with 
he
RL> DS> problem I am having now.
RL>I'm almost positive that it wouldn't.  Improper bias will either kill your
RL>tone or burn the tubes out.
Yeppers
RL> DS> Also, is there some way to adjust the bias on Randall amps that I 
ust
RL> DS> don't know about?
RL>Bias can alsway be adjusted, just not always with a screwdriver.  Often,
RL>you'll have to change one or more resistors.  That's how my Carvin is set 
up
RL>The schematic says something like "Select R22 for -28vdc from TP-5 to 
ground
Hmmm...I hadn't thought of that.  I will look into it.
RL> DS> If not, where can I get Randall tubes?
RL>Good luck.
Thanks...I'll need it
-dug
 þ SLMR 2.1a þ
--- Michiana Mail Center
---------------