It is most likely the reed relay contacts sticking on the input side, not the
vacuum relay.
GL!
(((73)))
Phil, K5PC
Don Moman wrote:
> Lost the receive path somewhere in the Alpha 77DX just before the end of
> the WPX test this past weekend. The direct/aux slide switch has been
> by-passed so that isn't the problem. Transmit works fine. receive had
> always worked fine before.
>
> What I've seen so far: Antenna is routed fine from a cold start and thru
> the 3 minute warmup. The first time it keyed it after that, it took a 1/2
> second or so to get rcve back, next slightly longer and then quickly
> refusing to work after that. Thumping the case had no effect. If you shut
> the amp off, the rcve will come back in a few (5 to 15) seconds maybe.
>
> What to suspect? Well the vacuum relay is about the only thing in the
> path. So measuring the pull down point (Q301) on the QSK board showed that
> to operate fine (55 volts pulled low when keyed, then comes back up
> quickly). I thought if something was leaking here it might keep the relay
> switched in tx, but that doesn't seem to be the case. Yet something is
> keeping it energized as shutting the amp off lets the relay go back to
> receive.
>
> I haven't a spare vacuum relay to pop in, but that seems like the obvious
> thing to do, but in the meantime, anyone have any other thoughts? Residual
> magnetism holding it on or??
>
> 73 Don
>
> VE6JY Don Moman email: ve6jy@freenet.edmonton.ab.ca
> Box 127 Lamont, Alberta email forwarding: ve6jy@rac.ca
> CANADA T0B 2R0
> (780) 895-2925
>
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