"Russell W. Barnes" russell dot barnes @ huttonrow dot co dot uk wrote in
message news
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.


I'd suspect a break in the ground circuit between the front panel and main
ciruitry or in the uP area. As you've checked joints etc, maybe a cracked
PCB track?

Navico still exist but under a the name Simrad and are still in the
Broadstairs area. I'd be surprised if they have anyone who remembers this
set you can talk to but they may be able to supply a circuit.

73

Brian