[Heathkit] SB-300 Question

[KHeck73 at aol.com]

In a message dated 11/12/2005 7:38:11 P.M. Eastern Standard Time,  
w3wjr at aol.com writes:

I just  received an SB-300 with a small problem. Before I dig into it, I 
figured I  would ask for hints.

Unit works pretty well as long as you leave the  outer jacket of the coax 
disconnected. When its connected the receiver goes  deaf.



..
Great question, because I have an SB301 that does the same thing. The coax  
is not shorted, and it happens even without the coax shield being grounded  to 
earth. The unit receives fairly well with only the center conductor  
connected. I also note that the chassis has a slight voltage on it. I get  weak sparks 
when connecting or disconnecting the ground wire. I connected a  voltmeter 
between the chassis and earth ground, and a voltage slowly swings  about plus 
then minus 80 millivolts in a six second cycle. This might be normal,  I don't 
know. But, I think the problems could be related because the  receiver blanks 
out stronger from the coax shield effect when the chassis  is grounded. 
Something is slowly charging and discharging,  but that's as far as I got.
 
-Karl.