Ken -
Have you tried adjusting the input variable cap on the input of the 9-meg
board?
It is worth a try, worked for me. Was a simple fix.
73 - Don
----- Original Message -----
From: "Ken Brown" <ken.d.brown@hawaiiantel.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Friday, May 30, 2008 2:10 AM
Subject: [TenTec] Omni VI problems, continued
> Hi all,
>
> Changing C19 on the XTAL OSC LO MIXER BOARD did not make any big change
> in the power output, and I can still hear a periodic "relocking" sound
> when on 30 meters (maybe on other bands too). By scoping the output of
> the LO board, I can see that on bands with low TX power output, the
> output of the LO is also low (relative to other bands, I don't know what
> it should be), so I am suspecting the that the last TX mixer, U1 on the
> BPF/FRONT END BOARD is starved for LO power. I also see on some bands
> there the LO signal appears on the scope as multiple tones. I am doing
> this all in CW mode, so I don't expect to see anything but constant
> amplitude sine waves anywhere in the transmit signal path. I am not too
> concerned if they are not pure sine waves, but if they look like
> multiple tones, or modulated it seems like something is wrong. Maybe the
> carrier balance in the LO MIXER is off, letting some of the 5 MHz VFO
> signal through.
>
> The next things I'll try is to get all of the XTAL OSCillators adjusted
> for "minimum stress", which is to have the PLL correction voltage as
> close as possible to nominal, whatever that is, and I'll check the LO
> mixer carrier balance. Based on the values of R25 and R26 (which are 1k
> and 470k) I think I can connect a 10 Meg scope probe at connector 84 to
> monitor the DC voltage there, without severely disrupting the circuit.
> Does anyone know what the DC voltage at 84 is supposed to be? I guess I
> can determine the full range of DC voltage there, and then set the XTAL
> osc tuning coils for the center of that range. I'd sure rather have a
> specification to aim for.
>
> By the way, if anyone is wondering why I don't just sent the rig to
> Ten-Tec for service, there are a number of reasons. Shipping cost both
> ways from Hawaii would be many times the cost of any parts that need to
> be replaced. If I had Ten-Tec fix it I would not learn much.
>
> DE N6KB
>
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