[ICOM] 751A Transmit

[Paul Gates, KD3JF]

How do you think this all came about?
Paul KD3JF

EP Swynar <gswynar at durham.net> wrote: Good Day All,

My venerable 751A put up some very strange behaviour yesterday, after having sat idle for some 3 months...I wonder if anyone reading this might have a suggestion, or two, before I open the rig up later this afternoon? Any & all feedback / comments are not only welcomed, they're hereby being solicited! Hi Hi

Specifically, I fired up the rig to transmit on 40-meters and the power output meter showed nearly 150-watts! I reduced the drive control COMPLETELY counterclockwise, & it STILL put out the same power...

The carrier would stay continuously "on", too, dropping off ONLY when the VOX did. 

This strange condition was evident on both a dummy load, as well as a resonant antenna. All "peripherals" were removed, the grounding was checked --- status unchanged. I tried it on different bands, but the only difference was the power output, which varied from 100- to 150-watts (dependent upon the band). 

Finally, I tried 10-meters & the output suddenly dropped right off to zero --- I'm sure I popped the internal fuse with that last test.

It would appear that the finals in the rig are somehow "taking off" / self-oscillating, for some reason. I have not touched the rig in any way, shape, or form, since QRN took over 160-meters here last April.

I wonder if, by sitting idle like that, one of the interior connectors has somehow oxidized / deteriorated in the humidity of summer...?

In any event, I have to get inside to replace the fuse anyway, so I'll check those out...but I am curious if anyone else has ever had any similar such occurance with their 751A...

Thanks in advance, & vy

~73~ Eddy VE3CUI - VE3XZ
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