[Hallicrafters] HT-37 semi-QSK mod

[wb8jkr at juno.com]

  Has anyone ever done the factory semi-break in
keying modification for the HT-37 and had trouble 
with it? (Bulletin #094-902457)

 I had an HT-37 30 years ago with this mod and it
worked fine, but in the unit I'm working on now
the rig won't key in the MOX position. It will
key using a key in the CW jack, but will not
key when the function switch is in the MOX
position. I measure a -14 vdc on V14 pin 1,
a -38vdc on V14 pin 2, and a -14 vdc on V15
pin 2. I know this negative voltage is keeping the
relay tube biased off, and that's why it doesn't work, but
it seems to me the minus voltage would come from the
rig keying (bias) line so I don't understand how it could
ever had worked. I thought about installing a diode
to block the minus voltage from V15 grid, but again,
the original factory modification doesn't show one so I'd
rather find and fix the trouble rather than figure out a
possible way around it.  Any thoughts?

Mark  WB8JKR


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