{Collins} KWS-1 PA Socket Replacement



I'd finished the restoration of my KWS-1 and was in the process of doing the preliminary power up  testing.  The first time that I applied HV and keyed the PTT I did not see any idling plate current, but saw screen current.   I knew something was wrong and immediately removed the HV.  Shortly thereafter, I smelled something getting warm and removed power.   Investigating the PA base compartment, I saw that the small wire that went to the 470 2w and rf choke that feeds screen voltage to the tubes was broken and hanging.   I say broken because it was cleanly broken at the insulation like a mechanical break.   I don't know how the wire could've been mechanically stressed unless it happened in transport.   The KWS-1 was transported upright.

The 17ma in grid current that I was seeing was the current through the 20k safety resistor to ground.   Since there was no screen current through the tube, I guess that explains why there was no plate idling current.  The bad news is that the screen would've floated up to the HV level and blown the screen bypass capacitors in the tube socket and probably ruined the tubes?   
This same scenario would occur in a plate to screen flashover as well except in my case there was no high plate current.   Anyone had to replace the sockets before?  If so, what is the procedure?  Any source for the sockets?   Fair Radio?   Do the 4cx250b have to be a matched pair?

Dave, AG8B



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