[Drake] T4XC Carrier Oscillator, Filter Match, Mod Bal adj

[fkamp@comcast.net]

K6jek@aol.com wrote:

> I had very little luck following the procedure in the manual for setting
> carrier oscillator, filter match, and modulator balance.  I wonder if there is an
> alternate procedure.
>

I recently spent more time than I wanted on a T4XC doing the same thing.  In my case I
had a collector to emitter short in Q4 on the carrier oscillator board.  That problem
resulted in a 500hz carrier offset in all modes.  I could not tune out the offset with
C6.

After I found and replaced the bad transistor I had similar problems getting plate
current indication, so I used an swr meter as an indicator of relative power out.
Output of the transmitter was connected to a dummy load through the swr meter. SWR
meter was turned up to maximum sensitivity in forward direction initially and turned
down as needed..

I followed the proceedure in the manual except for using the SWR meter as an indicator.

I also used a frequency counter to set carrier oscillator frequency.  After I completed
the 'alignment' I discovered that I could only get about 10 watts out on CW on all
bands.  Went back and re-tweaked C6 and the transformers and got the thing to work up
to spec on CW.  Then went back and re-checked SSB modes to see what effect that had on
them.  USB and LSB seemed okay.  I have not yet figgured that one out.  Evidently my
frequency counter is not as accurate as it should be.

I believe there is a misprint on the manual where it goes through the carrier null
proceedure.  My manual recommends adjusting the null pot and C6.  I believe that should
be the null pot and C17.  If you fool with C6 at that stage, you mess up the carrier
frequency setting.

Regards,
Frank Kamp
K5DKZ