[TenTec] S Meter Problem with Omni V

[John Callari]

Frank:

I never made the adjustment because I didn't have a signal generator...  I wasn't going to 
fiddle with the R45 without having a true sense for what the actual signal strength was...
Plus, the Omni V was not going to be put back into service here, so I figured I'd leave it
to the person who bought it to adjust it to their standards...  :)  

Glad the Omni is safe and working well!

John
K2JNC

On Sep 18, 2010, at 7:28 AM, Frank Kirschner wrote:

> 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
>>> 
>> _______________________________________________
>> TenTec mailing list
>> TenTec at contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>> 
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec