Jim, it could be the T/R relay. This is the reed relay that switches the
receiver input to the antenna. If the problem is only on 1 or 2 bands,
check the underside of the bandpass board. Some of the coils used did
not take solder well and could be intermittent. I know thias happens
occasionally on the Corsair I.
73,
Bob WB2VUF
Jim Reid wrote:
>
> 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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