[TenTec] Help with deaf Argonaut 509...

[Joe Hutchens]

That should be "quiet" receiver... I found a schematic. If all the bands are week, it could be the antenna relay. Maybe one of the overload diodes on the receive antenna input is shorted.
--
Joe Hutchens ( AJ8MH )
http://webpages.charter.net/aj8mh-radio/

---- Joe Hutchens <aj8mh-radio at charter.net> wrote:
>
> I don't have a schematic anymore...so I'm winging it! Keep in mind that the 509 is a fairly quite receiver. The signals tend to stand out with good sensitivity. I was dumb to sell it.
> Let me ramble.
> 1. We need to assertain if you have a sensitivity problem or a problem that is just affecting the S-meter. (I think you have already narrowed it down to the frontend with your probe testing.)
> 2. How does the 509 compare with the 817 on the other bands? Are they all poor?
> 3. If the other bands are good, I would look for a bandswitch problem or a connector issue. It seems to me the boards do plug in.
> --
> Joe Hutchens ( AJ8MH )
> http://webpages.charter.net/aj8mh-radio/
>
> ---- Roscoe Primrose <roscoe at aiko.com> wrote:
> > On 1/28/09 10:45 PM, Joe Hutchens wrote:
> > > I've had the antenna selection switch on the back get dirty. Cleaning it solved my problem...back when I had a 509.
> > >
> >
> > Thanks for the idea. Bypassed the switch, no big deal since I'm not
> > using a separate receive antenna, no change in sensitivity...
> >
> > OK, who's next ;-)
> >
> > 73s, AJ4LL
> >
> > > --
> > > Joe Hutchens ( AJ8MH )
> > > http://webpages.charter.net/aj8mh-radio/
> > >
> > > ---- Roscoe Primrose<roscoe at aiko.com> wrote:
> > >
> > >> My Argonaut 509 seems to have a serious receiver sensitivity problem.
> > >> The other night when 80M was fairly noisy, I was getting noise at S6-S8
> > >> on an FT817, hooked the same antenna to the 509, an even with the RF
> > >> gain all the way up, the S-meter baorly moved, if at all. RF noise is
> > >> generally not enough to move the S-meter, and I've made several easily
> > >> understandable QSOs with no motion of the S-meter. The S-meter is
> > >> working, with very strong signals it does occasionally get up to S-9. I
> > >> originally thought the problem was the first stage dual-gate MOSFET, but
> > >> I'm pretty sure that's not the problem at this point. When
> > >> troubleshooting the first stage MOSFET, when I hooked a DMM lead to gate
> > >> 1 I get a stronger signal (not just noise, but signal as well) from the
> > >> test lead than I do from the antenna connected to the unit. On the RF
> > >> front-end board, the antenna signal goes through an input cap, a
> > >> transformer/cap combination that's a 9MHz trap (VFO), through a tuned
> > >> transformer which is part of the pre-selector, through a coupling cap,
> > >> and to gate1 on the MOSFET. Connecting the DMM lead directly to gate1
> > >> causes an increase in signal& noise, connecting it anywhere before the
> > >> coupling cap results in no change in signal level. I changed the
> > >> coupling cap, but there was no change in performance.
> > >>
> > >> Anyone familiar enough with the front-end on these rigs to have an idea
> > >> as to what I can check next?
> > >>
> > >> Thanks, AJ4LL
> > >>
> > >> --
> > >> "The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants. It is it's natural manure."
> > >> Thomas Jefferson, 1787.
> > >>
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> >
> >
> > --
> > "The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants. It is it's natural manure."
> > Thomas Jefferson, 1787.
> >
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