Jim Gerke <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Gary,
I need to go back and check the P-P voltage on the oscillator and PTO,
but they were both definitely working. I haven't tried changing the
pre-mixer tube yet, in part because the only other 6HS6 I have is
installed in a T4X-B that I'll have to open up. I haven't been able to
do any more troubleshooting since my post, but tomorrow will check to
see if both signals are making it to the pre-mixer stage, and what, if
anything, is coming out.
Just to be clear, there is no power output on any band at any preselctor
setting, other than with the bandswitch on 40m and the RF Tune (I said
preselector by mistake in my post) in the 80m range.
It has to be something common to all bands and the pre-mixer or mixer
are certainly good candidates.
I'll let you know what I find.
Thanks.
73, Jim K5JG
Garey Barrell wrote:
Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist
gang
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Jim -
If you are getting a preselector peak with the Bandswitch on 40M ONLY on
the 80M range, what is happening is that you are tuning the transmitter
Preselector to the Carrier Oscillator frequency of 5.645 MHz. This
indicates that one of THREE circuits are not working correctly.
1. The PTO is not running between 4.955 and 5.455 MHz. (5.455 MHz with
dial set to 0.0)
2. The Band oscillator is not running at 18.1 MHz
3. The Premixer where #1 and #2 above are combined into 12.645 MHz
Since you say you have 1 & 2 verified (both should be about 2 V p-p)
then either the 12.645 MHz signal is not being developed in the Premixer
stage, or if it is, it's not getting to the Mixer stage where it is
mixed with the 5.645 MHz Carrier oscillator to output 7.0 MHz.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs
<www.k4oah.com>
Jim Gerke wrote:
Jim Gerke <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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I have a T-4X that was working fine until yesterday afternoon when it
started keying itself, unkeying, etc., etc. It finally stopped, but then
it would no longer transmit. I changed the electrolytic caps in
accordance with info from various websites and it started working again.
So far so good.
Then, I decided to check out a couple of spare sets of Sylvania finals
to see what they were like. Put in the first set and they worked, a
little weak, but ok. When removing the cage to pull them and put in the
next set, I shorted the cage to one of the variable caps and SNAP! I'd
forgotten to disconnect the PS connector from the transmitter. At least
the PS was turned off at the time.
Since then, radio won't TX properly with any tubes installed, even known
good (100W-125W) ones. I can get output (25W or) only with the
bandswitch set to 40m and the preselector in the 80m range, but's it's
definitely not transmitting on 40m. I'd had this problem once before,
but in that case, the T-4X eventually decided to work again on its own.
This time, so far, it hasn't come back.
Final HV measures OK. Haven't measured the bias voltage, but I do have
proper bias indication on the meter. I have verified that the crystal
oscillator and the PTO are working using a 'scope.
Same symptoms using two different AC4 power supplies.
I'm still troubleshooting, but any suggestions that might speed up the
process would be appreciated.
73, Jim K5JG
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