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[TenTec] Omni D Update

To: TenTec@contesting.com
Subject: [TenTec] Omni D Update
From: "Carter, K8VT" <k8vt@ameritech.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 09 Feb 2006 18:04:12 -0500
List-post: <mailto:tentec@contesting.com>
Earlier, I posed a question to the group about an Omni D (Series B) that 
I was working on and promised an update upon completion of the job--so 
here it is.

First, thanks again to those who responded and also to John at TenTec!!

The original problem I noticed was that the 160 meter waveform going in 
to the final amplifier module was very distorted compared to the 80-10 
waveforms. This turned out to be an alignment issue. Adjusting the mixer 
balance (R2) on the "Osc-Mixer" board solved that problem.

As it happened (and unbeknown to me), the ALC diode was history. "So 
what", you ask. Well as I was checking the radio into a dummy load, I 
was pleased to note that I was getting 110-115 watts output (due to no 
ALC). To make a long story short, TT says the final transistors (MRF 
458s) are fairly delicate and won't tolerate very much over 100 watts 
out--so yes, you guessed it, one of the 458s is toast (open emitter).

I changed the ALC diode (easy), was fortunate enough to find a new, 
matched pair of 458s and replaced them (NOT a job for the faint of heart).

Bottom line, the radio is back in fighting trim again. And as John at TT 
says, every time an Omni D leaves his bench, it is set at 90-95 watts 
max output. A word to the wise.

Thanks again to all and 73,
Carter K8VT
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