[TenTec] fixed PTO in Century 21, but 40m seems a bit high on the dial
brianpepperdine at sympatico.ca
Tue Jan 12 15:07:02 EST 2021
Well, I won't say it took forever, but I finally got into the PTO in a decades
old C 21 I had. I did do the PTO after I got it originally, but then it sort of
went aside by the time I got replacement plastic cogs for the dial mechanism
from TT and I never got back to removing the front panel and all that. So.. the
PTO needed to be done again.
I had done about 3 TT PTOs but that was ages ago, so this was deja vu all over
Anyhow, I got it done. Got flummoxed by what I thought was no power getting to
the PTO (turned out to be a bad solder joint at the wire going to the two
lugs... whodda thunk?).
Anyhow, I started listening to it. 80m is about right on (using my freq counter
I see it at 5.245 on the PTO output for the 80m net on 3.755.).
But on 40m the CW section (bottom of the band) seems really high on the dial. It
comes in well above where I think it should be if the PTO is outputting 5.045
for instance. I changed the 40m mixing crystal for the crystal I have in
another (subsequent) C21 carcass and it is exactly the same place.
In a way I don't really care if 40m is high as long as I find I can somehow get
the whole of the basic 40m CW area (7.000 to 7.075 or so), but it would be
interesting to find out what's up. Since 80 m and 40m use the same mixing scheme
(ie. start a 'zero' and go up in freq by clock-wise rotation of the tuning knob)
I do wonder why the discrepancy.
I have a band specific standard freq gen for CW that is xtal based, so once I
unearth that I can see where 3.560, 7.040 and 14.050 are on the 'dial' as heard
on the band and as seen on the freq measured on the PTO.
The C 21 calibrator hears the 25 kc note at the same place on all the bands I
believe, so it seems to be mixing correctly on input versus mixing scheme with
the xtal for the bands.
There does not appear to be much regarding alignment of the PTO aside from
bottom end setting some degree of spread of coverage (and I am not certain I
currently have the tool required to adjust the two different sized coil holes
By the way, I had the choice of 3 greases I had at hand for this (each of them
will get used somehow, sometime, somewhere) but I chose a synthetic grease with
Teflon. I chose not to use the white lithium nor the brake caliper greases I had
seen also recommended (the second one looked too close to the original TT green
grease from the Tennessee farm co-op for my taste!!).
Brian VE3HI VE3VAW
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