[TenTec] S Meter Problem with Omni V

[Frank Kirschner]

Well, I assumed that if it were that simple, someone else would have made
the adjustment.  (Note to self: Don't assume.)

You're absolutely right: all it took was adjustment.  R45 was set at its
highest sensitivity.  There is also an S-meter offset adjustment.  I set the
S-meter to read between 0 and 1 on ten meters with no antenna connected, and
to read around S-9 or a little above for a local 80 meter signal.  It may
not be perfectly accurate, but it gives a good relative indication, and I no
longer worry about bending the needle.

Thanks.

73,
Frank
KK4PR

On Sat, Sep 18, 2010 at 1:31 AM, Dr. Gerald N. Johnson
<geraldj at weather.net>wrote:

> As far as I know the manual with circuit diagrams that you can download
> from Tentec is all the "service" manual there is. Looking at it I have
> found that there is an S-meter sensitivity adjustment R45 on the IF/AF
> board along with an S-meter offset R43. It looks like R43 sets the zero
> and R45 sets sensitivity from low to very high. I don't know the value,
> but there is no fixed resistor to limit hypersensitivity. Providing the
> AGC is enabled, you should be able to adjust R45 to any sensitivity you
> like, providing the pot hasn't gone bad with age. If the pot has an open
> resistive element it may only work set up way too high. The pot may have
> an identification resistance on it to allow finding a generic
> replacement or to allow a will guess for value, at about 1/2 the pot's
> total resistance to be put in as a fixed resistor.
>
> The other thing that can cause an S-meter to be hypersensitive is leaky
> bypasses on the AGC line so that AGC control is poor, e.g. that it takes
> a large AGC voltage to reduce the RF and IF gain. Maybe the RF gain
> controlled stage is on another board and the cable between them is open.
> It might be two common Tentec service procedures are in order. One is to
> tighten all the board mounting screws to make sure the grounds are good.
> The other is to apply a quarter drop of DeoxIT to each cable connector
> pin and slide the connector off and on a few times to get a solid
> connection again.
>
> If all that's needed is setting R45, you will have to judge by ear what
> signals are strong and weak, like we did before we could run AGC on a
> receiver on CW or SSB, and adjust the meter for a satisfying reading
> that matches your perception by ear.
>
> If R45 proves to be open, Cramolin who makes DeoxIT makes a pot restorer
> product that might work.
>
> 73, Jerry, K0CQ
>
> On 9/17/2010 7:54 PM, Frank Kirschner wrote:
> > I just bought an Omni V with the N4PY mod.  It works great, except for
> the S
> > meter.  I was told when I bought it that it was hypersensitive, and that
> is
> > true.
> >
> > Is there a "most frequent" cause for this?  I sold or gave away all my
> test
> > equipment years back, so can't do much exploration at this point.  I'd
> > appreciate ideas.  I have the regular operation manual, but no service
> > manual.
> >
> > Also, the knobs are a little greasy.  Is there a mild solvent people have
> > used to clean the knobs without removing the paint?
> >
> > Thanks.
> >
> > 73,
> > Frank
> > KK4PR
> >
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