[BC] Harris MW-5 question ( HELP !!! )

[donroden at hiwaay.net]

Just when I thought I would never have to look at a MW-5 again, I get  
a call from a local that is having a problem.

I haven't played with a 5 in over ten years, so bear with me.

No rf out    rf grid current fine

2000vdc on plate volt meter   0 amps on plate ammeter

No overloads

as far as panel metering, *no screen voltage indication* , but there  
is 430 volts on a wire-wound pot on the PDM board and 55 ohms between  
that point and the screen tube connector.  I am seeing some screen  
current  1/5 scale ( don't remember value ) but engineer thinks that  
is normal or a just a little low.

Haven't checked PDM out of the Modulator ... will return to site  
tomorrow with O-scope in tow.   I suspect this may be the area in  
question.

Couldn't someone substitute a variable bias supply at the 4CX grid and  
prove the operation of the RF tube and the Audio tube without  
involving the PDM generator ?

Any suggestions appreciated before this becomes a tar-baby.

Anyone remember the story of the tar-baby, or are you a product of the  
PC school system ?

Thanks for reading !!