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Re: [TenTec] Some progress made! --Omni D low to no power

To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Subject: Re: [TenTec] Some progress made! --Omni D low to no power
From: "Rick - DJ0IP / NJ0IP" <Rick@DJ0IP.de>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sat, 18 Feb 2012 12:59:00 +0100
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
BRAVO Scott, you are getting close.

My bet is that you have a defective Xtal filter.
Try bypassing just the Xtal filter.

Do the following:
 - remove the xtal filter completely
 - temporarily solder a .01 uF capacitor from the input of the Xtal filter
(coming from the secondary of T1), to the output of the filter (going to the
Pin marked "OUT", which is the second pin from the top if you are looking at
the schematic).  Or, just solder it across pins 2 and 6 of the output plug.

I'll bet you find you have 80w out when you do this.
If so, then it's the xtal filter that is broken.
 I dunno if you can still purchase one, but worst case, you can always use a
Model 220 out of the later Corsair and Omni V/VI rigs.  They are physically
a different size, so you'll have  to jerry-rig it.

Keep us posted.


-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of scottsheppard@videotron.ca
Sent: Saturday, February 18, 2012 5:37 AM
To: tentec@contesting.com
Subject: [TenTec] Some progress made! --Omni D low to no power

For those of you who have been helping along with the OMNI D low power
issue, here is the update:

I dragged out the fluke scopemeter tonight and did some checking...the
amount of power going into the Low Level Driver is very low as prev
mentioned...on the scope it was there but not much...when compared to the
output of the LLD, however,  big difference. Lots of gain on the LLD. That
was some good news. I checked the output from the VFO amp and that too
looked good (relative)...the next check was on the output from the SSB
board--again lots of output into the TX Mixer...the output from the TX
mixer, however, very low.

...I found the input from the LO into the TX Mixer which looked very good as
well and even the LO going into teh TX Mixer was 150 times more powerful
than the output from the TX mixer...something did not add up...

since I knew my LLD was better than first thought I decided to bypass the
crystal and band pass filters and bring the LO output into the LLD to see
what happened...Bingo...3 watts out of the LLD when sufficiently driven. 

Encouraged by that, I hooked up the PA again and put the power to it---80
watts out before any adjustment. Looks like everything downstream and
including  the LLD is A-OK...thats great news.

Now, it would seem the TX Mixer is the culprit OR it is still not getting
enough input...the relative signals into the mixer look good. One thing that
has me puzzled is why the signal output from the TX Mixer would show
continuity with ground??? yes, 0 ohms...it would sure explain a diminished
signal. I note that the output from the SSB board is also common to ground
(tx or receive) that goes through the crystal filter and eventually to the
TX mixer...I looked for shorts etc, no luck...perhaps a defective
component--or more likely a complex impedance through one of the
transformers etc...I got too tired check>>>nice to end the evening with some
progress for a change.

scott VA3IED

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