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[AMPS] Alpah 77DX rcve bypass problem

To: <amps@contesting.com>
Subject: [AMPS] Alpah 77DX rcve bypass problem
From: measures@vc.net (Rich Measures)
Date: Tue, 1 Jun 1999 02:51:48 -0700


>
>
>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??
>
-  my vote is for residual magnetism, Don.   As I recall, there is a reed 
relay in addition to the vacuum relay.  I would interchange the wires 
leading to the relay coils. 
-  cheers


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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