Seems like a much more reasonable plan. From the schematic the signals for
the relays originate on the logic board based on the
band selected from the keyboard. From there it traverses across a couple
of different boards until it reaches the connector on the lpf board
to activate particular relays. In tracing it through the schematics there
appears to be a couple of ICs that establish the voltage level on these
lines.
I'll clean/reseat the inter-board connectors and get a scope on these
lines to see what's happening. Since it only happens when the radio is cold
I can cool the IC's in the path to see if I can replicate the problem.
Thanks for the advice.
Terry, KI3C
On Sat, Feb 9, 2019 at 12:40 PM Peter Bertini <radioconnection@gmail.com>
wrote:
> Buzzing relays sounds like a problem on the processor board. But, I'd
> reseat all of the connectors associated with the band pass board first. As
> I recall, that starts on the micoprocessor board, and goes through the
> receiver bandpass board as well where some diode steering is done for the
> band ranges.
>
> At the very least, I would want to scope the band signals to see where the
> issue originates. Shotgunning the relays is not a good plan, and they do
> not fail in that manner.
>
> Pete
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