[TenTec] Omni C mixer PTO problem

[Rick - DJ0IP / NJ0IP]

Mike,

As you said, the reading on the counter display tells us the problem is with
the PTO.  Actually it can be the PTO, OSC. MIXER, or VFO AMP.  It won't be
beyond that point, unless something is shorting to ground and pulling it all
down.

TROUBLESHOOTING:

Once you have a scope or a frequency counter, you can troubleshoot the
problem MUCH better.

.  We have already ascertained that there is no jumper missing.

.  *** PLEASE TROUBLESHOOT ON 20M ONLY. ***  REASON: 20m does not use an
extra xtal oscillator and mixer.  All other bands do.  20m mixes the 5 MHz
directly with the 9 MHz LO of the SSB board. You have fewer stages involved
which could cause the trouble.

.  Measure the 5 MHz VFO signal.  The easiest place is right on the VFO
out/in jacks on the back panel..

.  If OK, also measure the 5 MHz again on PIN-5 of the Accessory Jack.  (on
20m, this is still just the 5 MHz signal, but at that point it has
successfully passed through the RX Mixer and VFO AMP board.  That's just a
quick check, but it's right there near the VFO jacks and easily accessible.

.  If the signal is not on PIN-5 of the Accessory Jack, then go directly to
the VFO AMP board (80454).  You should have 5 MHz on PINS 2, 4, and 6 of the
plug.  If missing on all, then the problem is back in the OSC. MIXER board
(80455) - or the cable to it.  If missing on some, then the problem is on
that board.

.  On 20m, the VFO 5 MHz just passes through the OSC MIX board, via D1 and a
wafer of the band switch. You should see 5 MHz on the input side and on the
output side.  This is a tough board to work on because of the bandswitch.
You can't just simply remove it.  You should have a 5 MHz signal on both
sides of D1.

.  I don't think the problem is beyond the OSC. MIX and AMP board because
otherwise the counter would read correctly.

REPAIRING:

. I think you should start by lifting and reseating the VFO AMP board
(50454).

.  You may not be able to lift the OSC. Mixer board (80455) but maybe you
can remove the screws and move it up and down a millimeter or 2, just to
clean the contacts.

.  What you do after that depends on what you found when measuring above.

Hope some of this helps.

73
Rick, DJ0IP







-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of Michael Silevitch
Sent: Tuesday, February 21, 2012 12:53 AM
To: Discussion of Ten-Tec Equipment
Cc: Michael Silevitch
Subject: Re: [TenTec] Omni C mixer PTO problem

Dear Scott

I will bring home some test equipment from the university where I teach.
That should help give me some valuable info. I'll keep plugging!

I owned a Triton IV for 30+ years and am now "upgrading" to the Corsair
and Omni C series. I do like the engineering that went into these Ten Tec
rigs.

Regards
         Mike K1PEV