[TenTec] No SSB TX from Omni D

[Kenneth Stringham]

Hi Jay,

My first question is: do you have the Operator's
Manual. This includes a detailed description of the
circuitry and the schematic. If you do not, I have one
here that you can purchase, I sold my 546C recently
because of my need for cash.

You problem will be located by looking at the SSB
generator board. This radio generates the CW signal by
moving the Carrier Oscillator 750Hz so it is inside
the filter pass band and then it unbalances the IC
balanced modulator. My guess is that you have problem
with the circuitry that moves the oscillator frequency
for LSB/USB. The frequency is offset to far down the
filter pass band. One of mine had a defective balanced
modulator IC which I replaced and all was well.

If you would like a consult on this problem, I am
available at:

1-617-817-6167

This is my cellar telephone number. We can get
together at your convenience and I can walk you
throught the steps to determine what is wrong.

Concerning the test equipment that you will need:

You need to have an Oscilloscope with 50Mhz of band
width. This will permit you to directly view the
signal envelop. Another HAM suggested that you need an
AC VTVM. This would be nice, but the correct
Oscilloscope will suffice. The critical item that you
will need is a good frequency counter. My guess is
that you will have calibrate the LSB and USB offset
frequencies and the 10KHz offset for the higher bands.

Let me know if I can be of assistance. Otherwise,
please contact a local Elmer who can provide the same
level of assistance.

Ken Stringham ARS AE1X

P.S. See my profile on QRZ.com. You can view my
website as well at:

www.geocities.com/ae1x

AE1X:kes

--- Jay Eimer <kd5wlx@familynet.net> wrote:
> Guys,
> 
> I have recently acquired a Ten-Tec Omni D Rev B
> transceiver.  Everything
> seems to be working fine, except I can't get any
> drive on SSB.  CW power out
> is fine (in fact, possibly too fine, as I can peg a
> 200W meter).  But when I
> key the mike in sideband, the meter tweaks up to
> about 10W, then slowly
> fades to zero over about 1-1/2 to 2 seconds.
> 
> At first I thought I might have had a bad mike,
> since it doesn't match the
> radio.  But I've since tried 4 others (none known to
> be good, but what are
> the odds....) as well as one "modern" mike, that's
> only 600 Ohm, but wired
> through a step-up transformer to 25K Ohm, and I do
> know that it is good.
> All the mikes will key the radio in VOX, and hold it
> keyed as long as I'm
> talking.  However, none will light the ALC light, no
> matter how high the
> drive is turned.
> 
> Checking in the manual, I decided to check voltages
> on the SSB Gen board
> (part 80499).  Here's what I found (only the
> discrepancies noted - assume
> the rest checked normal).
> 
> Pin Voltages:
>     SB-N Tx    CW 13.5 instead of 13.8 and BFO 5.0
> instead of 5.7
>     SB-N Rx    BFO 5.0 instead of 5.7
>     SB-R Rx    BFO 5.5 instead of 5.9
>     CW Rx        BFO 5.0 instead of 5.9
>     Lock Rx        BFO 5.25 instead of 5.8 and T 0.7
> instead of 6.6 (biggest
> error).  The rest are within 0.1v of the book.
> 
> All of the transistors check out okay.
> 
> The ICs, on the other hand:
> IC1 - Tx - pin 1, 4.4. instead of 5.4
>         pin 2, 4.4 instead of 2.3
>         pin 3, 4 instead of 0!!!!
>         pin 4, 0, normal
>         pin 5, 1.5 instead of 5.4
>         pin 6, 4.4 instead of 7.7
>         pin 7, 4.4 instead of 6.6
> and pin 8, 8.2 instead of 7.7
> 
> IC1 - Rx - pin 1, 4.4 instead of 5.5v
>     pin 2, 4.4 instead of 0
>     pin 3, 4 instead of 0
>     pin 4, 0 instead of 1.6
>     pin 5, 1.3 instead of 5.5
>     pin 6, 0 instead of 8
>     pin 7, 4.5 instead of 0
> and pin 8, 8.2 instead of 8
> 
> IC2 - Rx - (disclaimer, I was unable to find the
> "mark" for pin 1 as
> indicated by the manual, so this is a best guess
> based on the position on
> the board - I would have hoped the measurments would
> line up....)
> pin 1, 8 instead of 4.1
> pin 2, 0 instead of 4.1
> pin 3, 8 instead of 4.1
> pin 4, 5.5 instead of 0
> pin 5, 0 instead of 3.6
> pin 6, 0 instead of 4.2
> pin 7, 0 instead of 4.3 and
> pin 8, 5.5 instead of 8v
> 
> Any ideas on what part might be bad?  Caps? 
> Somewhere else besides the SSB
> board?
> 
> All help very much appreciated, as I just recently
> got my upgrade and I'm
> desperately trying to get on HF.
> 
> Thanks,
> Jay
> KD5WLX
> 
> 
> _______________________________________________
> Tentec mailing list
> Tentec@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/tentec


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