[TenTec] Omni VI+ S meter troubleshooting

Phil Erickson phil.erickson at gmail.com
Fri Nov 16 23:41:11 EST 2018

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 -

Phil W1PJE

Phil Erickson
phil.erickson at gmail.com

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