"Byron Tatum" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Rich-
Sounds like crystal osc not working, as TR-3 works without the premixer
(VFO beating against crystal osc) on 80 and 20. Bad crystals are my #1
suspicion.
Use a VTVM or high impedance voltmeter and check for oscillation (as
described in manual): connect meter to Test Point and check for negative
voltage (about -5 volts or so).
If the crystals are oscillating then I would check voltages around
premixer tube. If OK there I would adjust the injection coupler transformer
for one of the bands just to see if someone diddled with it, but that is
pretty remote there.
I like to use the 6GH8A in place of 6U8 or 6EA8 for a little more "kick"
in both mixer and premixer.
CUL, Byron WA5THJ.
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, January 18, 2008 10:32 AM
Subject: [drakelist] WeakTR-3 transmit on 40, 15, and 10 meters
I'm restoring a TR-3 transceiver. I've cleaned it up, tested the tubes,
and carefully cleaned the switch and relay contacts. I find that I'm able
to get about 100 watts CW on both the 80 and 20 meter band. The receiver
seems to work fine for these two bands. The other bands are very weak.
In fact, I get nothing out on 40 meters and only about 1 watt max on the
other bands. I suspect the crystal oscillator. I replaced the 6EA8 tube,
things improved very slightly on 15 and 10, but still no power out on 40.
There is a test point available on tube V1a. I put a scope probe on the
test point, but I don't see a signal. Well, I see just some 60 cycle
ripple on 40 meters. On the other bands, there may be a very small
oscillation superimposed on that, but I can't tell. If I put the probe
near the tube, I pick up what looks like an HF oscillation on 10 and 15
meters.
Does anyone know what the signal on this test point should look like?
On receive, the 80 and 20 meter bands appear good. I can receive strong
stations on the 40 and 15 meter bands, but I think the receiver is
partially deaf. I don't know how good the 10 meter band is. There isn't
much activity on that and these days. I suspect the 40m crystal, but if
it were bad, I would expect it to be totally deaf on 40m. I thought
perhaps something might be wrong with the band switch, but I've cleaned it
up pretty well.
Any suggestions on how to proceed troubleshooting the transmitter?
The rig came with a Collins hand mic. I find that I get poor audio when
transmitting SSB (on the two good bands). I get a only a few watts out in
SSB. I suspect that the mic impedance is wrong. There's a transformer in
the mic. The element measures 4 ohms. I could possibly change the
transformer or increase the mic gain. I'm reluctant to change the mic
gain, but I think I could lower R94 to boost the signal. Anyone know
what they put in these things for a transformer?
Rich KE1EV
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