Hi all,
Today I had a chance to open the Omni up, desolder the S meter and get
the face off. Indeed, the needle was good and stuck mechanically against
the internal spring. Gary W0DVN had the answer: not even a 1/4 turn CCW of
the tension pot freed everything up and now it's working fine! Thanks to
all for the suggestions.
While working with a calibrated signal generator, FYI, I discovered that
even with the S3 and S9 points set correctly with the adjustment pots, the
S meter scale is definitely not linear (1 S unit = 6 dB) in between those
marks. Not too surprising - it's not a SDR after all. I've already made
up a calibration table in case I really need to know.
73
Phil W1PJE
On Tue, Nov 20, 2018 at 10:17 AM ROLAND HOWELL via TenTec <
tentec@contesting.com> wrote:
> Hi PhilUsing a jewellers loupe or similar check to see if there is any
> crud lodged between the magnets and the meter movement, just a piece of
> fluff or some such obstruction, even tho' the movement is sealed somehow
> things work in, I had a 'thrip' that's a very small crawling thing that
> comes from the corn harvest, they get everywhere and yes into my meter
> movement.
> Snowy G0HZE
>
> On Tuesday, 20 November 2018, 14:23, Phil Erickson <
> phil.erickson@gmail.com> wrote:
>
>
> Hi all,
>
> Spent a few minutes more with the VI+. I hooked it to a dummy load and
> keyed the transmitter in TUNE mode. With the knob on FWD power, the meter
> did move in sync with the power being drawn from the DC supply (15-20 A
> depending on mode), so the meter movement appears indeed not to be
> completely dead.
>
> However, it's sticky. On the FWD meter setting, when you raise the TX
> power and then turn it back down, the needle gets stuck midway on the dial
> and won't go down to zero. Firmly tapping on the front face does
> eventually get it to zero out, and then you get one pass from zero to max,
> whereupon it sticks again when the power is turned down.
>
> Obviously this is not very useful. Anyone know how to unstick or
> recondition this kind of movement? Maybe there is some old-time collective
> wisdom I don't know about. Or am I resigned to finding a new S meter from
> someone's surplus pile? [If so, who has these kinds of surplus parts now?]
>
> Cheers/73
> Phil W1PJE
>
> On Sat, Nov 17, 2018 at 6:17 AM Phil Erickson <phil.erickson@gmail.com>
> wrote:
>
> > Hi Jim,
> >
> > Thanks - already checked that part out with the S meter unplugged. I
> > could adjust R25 through its full range and see the voltage on a DMM go
> up
> > and down, so the pot wasn't at a dead spot, but I could certainly see
> where
> > this might happen in other cases.
> >
> > 73
> > Phil W1PJE
> >
> > On Sat, Nov 17, 2018 at 12:51 AM <w3ka@lycos.com> wrote:
> >
> >> Phil OM,
> >>
> >> I had similar issues with my TT Omni 6+. S meter readings were there
> >> but extremely low.
> >>
> >> On the IF/AF board, there is an S meter adjust pot, R25 a 1K trimmer
> >> control. Mine was
> >>
> >> sitting on a "dead spot". Gently rock the pot up and down, (not too
> >> much, just enough to free the dead spot on
> >>
> >> the trimmer).. World great on my VI+ and resolved the S meter issues.
> >> Good luck
> >>
> >>
> >> 73, Jim W3KA
> >>
> >>
> >>
> >> On 2018-11-17 04:41, Phil Erickson wrote:
> >>
> >> Hi all,
> >>
> >> I've just acquired an Omni VI+ with all the filters including the Inrad
> >> roofing filters. It is very sensitive as far as RF goes on all bands
> >> using
> >> a HP 8640B signal generator as a calibrated source. However, the S
> meter
> >> does not work at all when AGC is enabled (or for that matter, when it
> >> isn't, although of course AGC should be on to generate a reading).
> >>
> >> I pulled the covers off and examined the IF/AF board. According to the
> >> manual section 4-7, the voltage driving the S meter is at connector 58
> (a
> >> 2
> >> pin one). I pulled the connector off and, using a multimeter, was able
> to
> >> verify that a correct voltage was there on the pins in the ~200 to 800
> mV
> >> range. I was able to make that voltage go up and down as expected by
> >> manipulating the RF gain, and also by changing the signal generator's
> >> amplitude. The R25 and R29 trimmers also made the voltage move up and
> >> down
> >> as expected ("full scale" and "offset').
> >>
> >> So I think the S meter driving circuitry is working fine in RX mode
> from
> >> the IF/AF board..
> >>
> >> However, the manual is not clear on how the meter is multiplexed with
> >> the
> >> TX section, which I haven't tried yet as I'd like to get the receiver
> >> going
> >> first. I tried moving the meter selector knob to a few positions, but
> of
> >> course all of those are for when the TX is engaged (FWD, SWR, Ic, PROC)
> so
> >> it did not help.
> >>
> >> Does anyone have suggestions?
> >>
> >> 1) Maybe the meter movement has failed? If so, does anyone have any
> >> tips
> >> to isolate the meter and drive it with an appropriate voltage to see if
> >> the
> >> needle moves?
> >>
> >> 2) Is there any other check to see if the meter is somehow not paying
> >> attention on RX because it's stuck on one of the TX meter settings?
> >>
> >> 3) Are there any other connectors to reseat?
> >>
> >> Thanks in advance -
> >>
> >> 73
> >> Phil W1PJE
> >>
> >>
> >>
> >>
> >
> > --
> > ----
> > Phil Erickson
> > phil.erickson@gmail.com
> >
>
>
> --
> ----
> Phil Erickson
> phil.erickson@gmail.com
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--
----
Phil Erickson
phil.erickson@gmail.com
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