[TMC] PAL-500 Amp troubles

[telegrapher@att.net]

After fighting on and off with my PAL-500 amp and power supply i think
i've got the answer.  

No screen voltage was my original assessment.  Why?  Screen dropping
resistor was split wide open.  great.  Where do you find an 80K 50W
resistor?  No such luck.  So i put in a 50K 50W and 25K 50W, close
enough.  

WHAT?  Still nothing?  Check screen dropping circuit again.  How come
them 2 resistors are open?????  Get a couple of replacements and finally
decided i'd wire them in.  Before applying power, Check regulator tubes,
string of 5-20Meg resistors in the meter string as well as the 100K 20W
bleeder.  All ok there. Everything in the power supply is hunky-dory, so
i think.....  Hook up the amp to the power supply.  Go thru the
pre-start checklist.....Apply voltages per manual checklist.  I can get
about 40W out and input tunes up nicely.  Still something is wrong. 
Sure feels hot around them 100W worth of resistors.  Shut everything
down and disconnect the interconnect cable.  Recheck power supply
readings.. Everything ok still.  Hmmmmm.....

Look at pin 3 of cable towards PA which carries the screen voltage. 
WHATS THIS GROUND?  Manual doesn't show it and i know you shouldn't see
a ground on a terminal where 360V sets.   RATZ!!!!

Pull cover from PA.  Pull tubes.  GROUND is gone!  Yippee.  Defective
4CX250B....  Yeah right.  Left socket with tube in it is clean.  Place
tube in right socket (as viewed from front) and ground reappears.  It
appears the socket is where the trouble is.  

Funny thing is that you only see the trouble with one tube in place. 
Screens are tied together.  Must be something that only appears when a
tube is inserted into the socket.  

Anyone have any experience in changing out those type sockets?  Looks
like i need one also.  

This is disgusting.  How could the guy who sold this to me have stated
that it was working when it left his place?  

Live and learn.

Need socket for 4CX250B/4CX350 tube.  No indication in the manual as to
the type other than "air socket".

Larry
W0OGH