[Boatanchors] Disc Ceramic Caps

[Singley, Rodger]

Curt,

If you haven't done so already, interchange the 6CL6 tubes in V1 and V2 positions to rule out trouble with the 6CL6 oscillator tube.  Also, heater/cathode leakage in the 6146 tube can also cause issues with the keying line.

Ceramic caps are reliable but any component can fail.  After 3 months of usage a brand new 500 volt mica cap (new production from Mouser) failed in a circuit in my Pierson KP-81 receiver and the cap was never exposed to more than 5 volts so anything can fail.  Also make sure there isn't leakage on the tube socket due to buildup of dust and foreign matter.

Rodger WQ9E


-----Original Message-----
From: boatanchors-bounces at mailman.qth.net on behalf of Curt
Sent: Mon 8/30/2010 7:08 AM
To: Boatanchors at mailman.qth.net
Subject: [Boatanchors] Disc Ceramic Caps
 
Recently acquired a tired old DX-40 with keying issues. Slight frequency 
change after key-down ( chirp ), now sometimes will not stop oscillator on 
key up. So, evidently something is causing the keyline to stay low?

Don't usually suspect low-value disc ceramic capacitors like used to bypass 
the key line to ground.  Is there a failure mode for these that would cause 
them to short out intermittently?

Thanks, Curt KB5JO 

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