Hi to all,
Well, now am absolutely convinced my Corsair II is occasionally
not hearing too well, particularly low level CW signals
are NOT heard/copied that are just fine on both the
Triton 544 and Omni VI+! The RF preamps in each of
these rigs differ from one another. I am going to assume
that is the site of the problem as all else seems fine in
the Corsair.
In the Corsair II, the RF preamp is Q3 on the RF Mixer board,
#80987; this is a simple transistor. In the Triton, the RF
preamp is a dual gate MOSFET, while in the Omni VI+, the
RF preamp is a group of low NF grounded gate configured
FETs. Or, the RF front ends are different in each of these
TT rigs.
Now, my Corsair II was at TT back in August, '00 for a number
of fixes, PTO rebuild, etc. -- the complete TT Service Dept.
treatment! A month after receiving it back out here in Hawaii,
I had to return it again as the transmitter wouldn't transmit.
The no charge fix that time was reordering the low level driver
board connections, reset the ALC, and signed off as tested
on all bands.
I am sort of convinced that this radio, now some dozen or so years
old, is suffering from "old age" at least as far as traveling around
via Fed Ex goes! So am reluctant to return it once again to
Tennessee, as it was there only 7 months ago.
All the CW beacons on 15 and 10 meters are easy to hear/copy
today on both the Omni and Triton; on the Corsair -- silence,
only the hiss of noise. Stronger CW signals can be heard,
for example the K5 land beacon up at 28280, and many SSB
signals on 10 meters. Other indicator about the Corsair is
a very seldom moving S meter; again an indicator, I believe
of only low level RF/IF signals getting to/through the IF/AF
board # 80984 on which the AGC and S meter circuitry lies.
Another point, this "partial deafness" seems to be there
at one time, and not at another. For example, when
I started this note, the "deafness" was in place. After
nearly finishing this note, I have come back to the
Corsair, and it now seems to be hearing weak signals
again!!
I suspect that the problem may not be the RF amp transistor,
Q3 on 80987, but maybe a joint/connection which is
"occasionally" not good; maybe temperature sensitive,
or to a slight jiggle of the operating table (though this is
pretty heavy and stable). or......?? Assume this joint
problem would be on, or near the 80987 board, true?
Even on a very, very weak signal, the signal to noise ratio
still "hears" to be better on the Triton than when using the
Corsair, even in the apparent "good" state of operation.
Too bad it is not a tube rig, and I could just pull and
change tubes, hi.
May have to call TT service dept. again, phooey.
73, Jim, KH7M
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