[Yaesu] FT-1000D - slight lightening damage to (modified) LPF unit
Chris Codella, W2PA
w2pa at arrl.net
Tue Jul 5 13:42:28 EDT 2005
I had some minor damage due to a close-by lightening strike. So I'm now
in the process of diagnosing the problem and figuring out which parts to
replace - wondering if anyone else has seen similar things.
The damage was confined to the LPF unit on top of the rig so it's easy
to get at. There is a circuit that switches the receiver in and out of
the antenna path using a 12V relay, three transistors, and a diode (and
other peripheral components) - this is what has stopped working
(resulting in no signal to the receiver). Something got fried,
preventing the relay (RL7218) from switching the receiver in. It looks
to me like the culprit is the Q7202, Q7201 combination. I suspect Q7202
since it doesn't seem to switch off - looks like a collector-base short
and/or base-emitter open. Also, the isolation capacitor C7678 seems to
be leaking as there is voltage on the "ANT" terminal.
The other interesting thing is that Yaesu seems to have modified my LPF
board since the circuit is different than the one in the manual's
schematic. It was either done at the factory in 1991, or was done back
in late 1992 when I sent it back for some warrantee repairs. The manual
shows the collector of Q7202 driving another NPN (Q7203) that pulls one
side of the relay to ground (the second side is tied to the 13V line) to
enable the receive path. Mine, however has it changed around so that
instead the collector of Q7201 drives a new PNP that connects the relay
to the 13V line, with the second relay line tied to ground. Q7203 and
its associated components are gone completely.
Have any of you seen this modification?
Have any of you had similar lightening damage to the LPF unit?
Thanks, 73,
Chris, W2PA
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