[Heath] SB seriesVOX problems

[George Babits]

Greetings,

I'm working on a SB-110 (still).  In moving on to the transmitter section I 
find that the VOX hangs up.  Sometimes it will just do go to transmit mode 
on its own.  Other times it will trip normally but then not release.  If I 
lower the medium voltage from 250 down to 230 or so and put about 15K in 
series with the relay coil, the problem goes away.  I finally put a ma meter 
in series with the relay and see that 7 ma flows through the coil when the 
tube is supposed to be "cutoff."  Obviously it isn't cutoff.  Even with 15K 
in series the tube is still drawing 3 ma or so.

My mind keeps coming back to the zener diode in the cathode of the relay 
tube (which I have already replaced).  I am considering reworking the 
circuit to eliminate the zener and more or less duplicate the circuit used 
by Collins and Drake.

In comparing circuits I see that this is identical to the SB-101/02 series. 
I have been told that what I am experiencing is a common problem and that 
there was a simple modification which could be made to correct it.

Anybody have some information on the modification?

Thanks,
George
W7HDL