Doug -
No, the transmitters should work just fine "standalone".
It's highly unlikely that two transmitters would have exactly the same
failure / symptom, so you're probably "missing something"....
First, do you know if either (both) transmitters have been modified for
transceiver service, TC-2, TC-6, etc.? If they have, there will be two
RCA jacks near the center of the rear panel, possibly marked "A" and
"B", depending upon serial number. IF the jacks are there, (not just
holes,) you'll need a jumper cable between them. They are there to
interrupt the screen voltage to the Final stage ... No screen voltage,
no plate current!
If this is NOT the case, a bad V9 is the first suspect. Again, highly
unlikely that the same tube is bad in BOTH transmitters, but we gotta
start somewhere.
The operation in TUNE mode is that the MIC AMP, V9a, is converted to a
phase shift audio oscillator via some switching. This ~ 1000 Hz tone is
fed to the Balanced Modulator, and goes from there just as if you were
whistling into the mic. The same audio tone is fed to the VOX circuit,
and is used to close the T/R relay via V9b, V1a, V10a to V10b which keys
the relay.
So if you can hear the relay click when you switch from SSB to TUNE mode
and "unclick" when you switch back, then the oscillator is working and
the problem is in the switching and cables to the Balanced Modulator.
IF the relay clicks IN and then immediately drops out, then the audio
oscillator is most likely NOT working and/or there is a problem in the
diode switch (CR15) or the following stages in the VOX channel listed above.
If still no luck, then further troubleshooting is going to be required.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
[email protected] wrote:
I am bringing back to life 2 each T-4XC's and 2 each AC-4's that
have been idle for over 15 yr. Both units are stock. I checked all the
electrical and mechanical connections for security. Checked and
cleaned the switches. Tested the tubes and reseated them with DeOxit.
I checked all resistance measurements with the Resistance Chart. I
connected a Dummy Load. Over a period of 3 days I slowly brought up
the combinations with a Variac. At 100 vac the high voltages are +650
and +250 vdc. I adjusted the Bias to .07 amps. Using the Tune-up
procedures, I go to Tune, rotate the gain control, and I get no meter
movement on either T-4XC. Question: Do I have to connect a R4C to the
T-4XC to get output. Right now it's just the T-4XC operating. Best
Regards to the Group. Doug
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