[TenTec] Before I call Ten Tec . . .

Mike Bryce prosolar at sssnet.com
Tue Mar 4 00:46:05 EST 2014


I’m going to shoot from the hip here.

I don’t believe you have a PA problem.

I suspect it’s a logic board failure.

The CPU instructs many of the circuits on what to do and when to do it.

The Omni VI is packed full of various signal diodes, they are biased on or off depending on what band the circuit is operating on. The bandpass and the output filter board is one of many like that.

I’d take a peek at the bandpass board because it’s easier to get to. You’ll see a multi wire connector on one end,  I’m doing this from memory, so you’ll need to look it up in your manual, 

Set your VOM to read voltage and start with the 160 meter band, you see +8 volts or so turning on that part of the circuit. Check each band and note wether or not you’re seeing the control voltages coming from the logic board.

If you find one of the bands that is causing your trouble is not being turned on, then work backwards toward the logic board. IT gets complex in there, but the microprocessor will select the send the proper voltages to the various boards depending on the band selected.

does any of that make sense to you?

mike, wb8vge

Mike Bryce, WB8VGE
 the heathkit shop
SunLight energy systems
J e e p

On Mar 3, 2014, at 10:04 PM, Jim Goudie <JAGoudie at comcast.net> wrote:

> Hello!
> Enter into this at your own risk ;-)
> I have an Omni VI opt 3 with a couple problems :-).  I've taken it apart, poked around with my limited skills and VTVM.  Resistance checks on the power transistors seemed ok.  R5 on the DC Input board (.015 ohms) checks ok and the voltage is ok.  I've exercised the connectors and put Deoxit on them...  But my problems persist as my ability to track them down doesn't.
> Here are the two problems -- may be related and may not -- and some of what I have observed...
> 1.  I was on the air sending cw when all of a sudden my power dropped to 0.
>     On all bands I get no power out.
>     The ALC light is on at Minimum Pwr setting (in Tune)
>     The ALC light goes out as the Pwr control is increased past the 9:00 position
>     Still no power.
>     I can hear the driver in another receiver; there is a signal going to the PA
>     When the ALC light goes out, as above,
>       I hear a second higher tone in the other receiver in addition to the main carrier freq
>       like something is going into oscillation...
>     The signal from the driver is keyed properly on CW.
>     On receive, the power supply shows about 1.5 amps being drawn
>     On "Tune" it goes up to about 2.5 amps... 
> 	with no change as I increase the power control
>     I also tried using a microphone;  no power, no response...
> 2.  On receive I only hear signals/noise via antenna, on 80, 15, and 10 meters.
>    On these three bands, the PBT works normally; 
>       switching to the rcv antenna (with none connected) cuts out the received noise
>    On the other bands, the PBT makes no difference in the noise heard,
>       and switching to the rcv antenna makes no difference either.
>     For some reason the signal at the antenna only gets through on 3 bands.
> Any tips, advice, before I call Ten Tec?  I have very limited test equipment!
> Tnx & 73
> Jim, AF3Z
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