Re: REPAIR JOB: NC-20, Part IV not long


From: David Fifield (
Date: Fri Mar 12 1999 - 23:06:13 EST


It sounds to me like you have a short between pins 6 and 7 of
the AFA (U10). With the rig powered OFF, measure the resistance
between these two pins. What is it?

The AGC loop times are not optimal - I'll give you that! I ran
out of design time to do this. However, some work has been done
on the AGC since the rigs shipped, and an nice modification is
in the process of being worked out. I think it will publish in
QRPp sometime....although, with the interest level it seems
to be generating, we may want to consider publishing it sooner!

72, Dave Fifield, AD6A

"Paul R. Valko" wrote:
> AGC is still really bad. Bad "popping" noise on TX. Very slow to
> recover >5 seconds.
> I still hear a beep beep beep... while the NC-20 TRANSMITS. It doesn't
> seem to be the AFA chip... I still get it in the headphones even if I pull
> the AFA output pin #7!
> I believe it is the so-called "39ms positive going pulse every .35ms" as
> described on page 19 of the manual.
> I don't know where that pulse is generated or HOW it is getting through to
> the headphones in TX.
> Answers greatly appreciated.
> 73! =paul= W8KC
> Collector of Ten*Tecs and other fine plastics
> <>

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