K9IG added after AK4XX's report of loss of reception on 7.5~14.5 Mc:
>I've found myself in a similar situation but with my Mark V. It is
>about 7 months
>old and has been sitting idle for about 3 weeks.
>
>I made a few Q's with it this weekend and let it sit idle for an hour.
>The
>main receiver is now totally gone, no receive, no hiss, no transmit.
>The sub-receiver
>does work on some bands, but it depends on what band the main receiver
>is set
>at.
>
>A master reset did nothing. A call to Yaesu resulted in the same.
>
>So, it's now in the hands of UPS and the world of warranty repair.
With so much not working, CPU being off in la-la land is a distinct
possibility.
I think Marko will find a switching diode for the 7.5~14.5 Mc input BPF
circuit blew.
Pop covers, set rig up on an effected band, then touch the inside of the
diode furthest "inside" from the antenna for the suspect BPF section, then
the inside side of the "outside" diode.
Sorry, I don't have the service manual here with me to be more specific, but
when a nasty SO2R incident left some bands deaf on my MP & an IC-765,
it was very easy to identify what had went by poking around with a
screwdriver - you should be able to hear receiver spring to life as screwdriver
acts as a mini-antenna & bingo, bad diode is identified.
1N914s work great until one can find a more appropriate replacement
component. And when you're not sure what blew the original diode(s) in the
first place, 1N914s are more suited to sacrificial duty.
In my case, something very nasty came out of an Alpha that blew internal
doorknobs to pieces & created an occasionally intermittent relay in an
external antenna switch. The two rigs were on antennas just 4m apart or
so & both had external BPFs. Alpha on 40m yet MP blew 15m internal
BPF diode. Alpha was not transmitting. 765 lost several bands' worth of
diodes in one go. Alpha still dead one year on (no time to fix). Extra
seemingly irrelevant info provided as after the smoke literally cleared, I
expected internal BPF passive components to have become toast, but it
was only diodes in both rigs.
Good chance you're just a diode (the one on the input side to the internal
BPF) away from getting rig fully operational again.
73, BW2/VR2BrettGraham
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