I have a Navico AMR-1000 2 Metre transceiver with a strange fault. I cannot
use the set to transmit, change freq. or illuminate the LCD display. In
other words, none of the panel controls work. Whenever the mic is removed
from the 8-pin socket, all is OK! However, when the mic is removed and the
display is set to 'channel' rather than frequency, the set starts scanning
through the band as soon as the mic is replaced.

It is NOT the mic or cable!

I checked out all mic and PTT, and the up/dn selector switches. With the
mic completely removed from the set and a 10K resistor is connected to the
mic pins at the set socket, it all goes faulty again. It is when a mic
impedance or equivalent is connected to the set that things go awry; all
switch-buttons are working normally.

The only thing to link the mic and the other functions is the control
processor, as a sniff of the mic is connected to the processor (HD4074608)
via a pad consisting of a 10K and 47 K resistor (toneburst output, generated
in the processor and fed to the mic - acting as a speaker - so it can be
heard when the PTT is operated). The fault is intermittent(ish) as all is
OK for a short time whenever I open the set up and remove the 16-way plug
linking the front panel to the main set, and replace it afterwards. I have
checked all connections and not found any dry joints.

I am rather hoping it is not the processor which is faulty! Have any Navico
users experienced a problem like this - and discovered what was doing it?
All info appreciated.

--

Regds,

Russell W. B.
http://www.huttonrow.co.uk

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