[Boatanchors] KWM2A

[Bill Cromwell]

Hi Bill,

What you are describing is in some of my service notes. It says one 
cause is a fading driver tube. It starts out with enough drive and then 
fades. Nothing will show up on a tube tester until it gets much worse. 
Do you have another (others) that you can substitute?

73,

Bill  KU8H




On 01/05/2015 04:07 PM, Bill and Liz wrote:
> I’m playing with a KWM2-A which has intermittent drive problems.  After turn-on, it may or may not produce grid current and, if it does, after a few cycles the drive disappears “until next time”.  Drive is always available up to the grid of the driver tube-the intermittent condition is after that.  I can find no blown or damaged components.  The only clue is that when drive is available it starts with a decent reading and then declines fairly quickly to about 1/3 of the initial meter reading.  I have tested the driver tube ; screen and plate voltages are always the proper value.  It is possible that it is a relay problem (driver tube is biased off in receive and switched by K2) but I inspected the relay, cleaned the contacts with paper and NuTrol and even rapped the relay with a screwdriver when drive disappeared, all to no avail.
>
> I’d hate to recommend to my friend that he replace the relay if the problem may lie elsewhere.  So, until I do that I wonder if anyone may have encountered this problem before or has any suggestion where else to look.
>
> Bill VE3NH
>
> PS-I posted some weeks ago about the oscillating regenerative IF in a homebrew receiver.  There was some coupling between input and output...poor building practice (parts laid across the tube socket-I should have seen that before I posted!)....but the real culprit seems to be that the tube has considerably more gain than is necessary and is sensitive to screen voltage (regeneration is in the cathode).  Right now I have the stage working but it still does not go into and out of oscillation as smoothly as I think it should .  So, still working on that one.
>