HQ-170C Mute Recovery Problem

[Bill Evans]

I am having intermittent receiver mute recovery problems
with my Hammarlund HQ-170C, used in conjunction with a
Johnson Ranger transmitter. On a significant number of
occasions when I release the D-104 microphone bar to
receive, the HQ-170C stays muted and will remain muted until
I give the PTT one, two, three - or as many as six  "pumps".
I employ an external TR relay, controlled by the Ranger PTT.

At first I thought the auxiliary contacts on the TR relay
were sticking, as a normally closed contact pair is used in
conjunction with the 170C relay socket to operate the
muting. However, everything works fine with the auxiliary
contacts themselves, which switch  -108 VDC to the RF stage
and the two IF amplifiers when the receiver is muted.
he  -108 VDC disappears instantly when I release the
microphone bar but the receiver may remain muted.  If I
don't clear the condition by pumping the PTT until the
muting drops, the receiver looks like it will stay muted
forever. (Power "off" and working all the other switches
does nothing to clear the condition.)

Can anybody suggest what the problem is in this situation?

Bill Evans, VE4UD
313 Carpathia Road
WINNIPEG, Manitoba, Canada
R3N 1T2
PH:   (204) 489-7434
FAX:  (204) 487-7199
E-MAIL: bevans at ebsys.mb.ca
Company Web Site:  http://www.ebsys.mb.ca