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,
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