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Old December 23rd 05, 06:17 PM posted to rec.radio.amateur.boatanchors
Chuck Harris
 
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Default Drake tr4c problem

TJM wrote:
Recap;

After TX (cw) when relay releases, the RX sounds some times muted but
still there, the S-meter will rise up the scale to about 40+ and the
rx freq is off a bit (like on the wrong sideband)
If I re-Key, all will return to normal...this problem will happen
about 50% of the time... looks like relay is fine), but more like the
mute curcuit is hanging...???


Relay cleaned but problem pops up when fully warmed up after 20+ mins,
I'm going to pick up a new vox curcuit tube (6fq7) and replace to
eliminate that... will post results.


Well, VOX tube,6fq7, replaced ( boy, they can be costly ) along with two
others in same section without luck... back to the drawing board. I
thought it was going to be an easy swap. Will recheck relay and then on
to voltage checks ( seems like heat condition )

Tom


Hi Tom,

Don't forget to take a look at the cathode resistor bypass
electrolytics in the Vox/relay driver section. They don't stand up
well to the test of time. Typical values are 10uf 15V. When they go
bad, the T/R relay will start to conduct partially all the time, which
can make even good contacts iffy.

It is (as I said earlier) highly unlikely to be a tube. Tubes are usually
an all or nothing affair.

-Chuck