[ICOM] Warning about W1GEE interface cables

[Gary Fiber]

Floyd,

Good on the 765 being not involved in the lightning strike. Any way to 
check the computer's serial port?

All the level's I remember off the top of my head is 0 and + 5 volts DC. I 
am sure there might be a tighter spec for the logic chip. Even though the 
CPU is likely cmos the CI-V buss is still based on TTL levels. Internal to 
the transceiver as you know a couple of transistors are used to interface 
to the CPU. Fortunately they are also the weak link most times when you 
experience an event like you did.

The CT-17 using the MAX-232 chip always worked fine, so you could base 
loosely the level investigation on that and go from there I suspect. One 
here posted the MAX-232 does not go to a full 0 volts, thats likely, seems 
to remember from about 1975 classes the spec for a TTL low was not 0 volts 
but something less than 1/2 volt. Geeze should remember that level but will 
have to consult a logic data book these days I don't use that information 
much so its buried in the grey matter. :)

Hope some of this helps.

Gary K8IZ


I just ordered an Icom cable from K1NU who says he knows his cables work
>properly with the 781 and 765.  Which gets back to the main point of my
>original post: W1GEE is selling interface cables WHICH HE KNOWS WILL NOT
>WORK with the 781 even though his literature says otherwise.  When I get
>caught up on the other repair work here, maybe I'll dig into it and see why
>it doesn't work.  I don't recall seeing anything in the 781 service manual
>about the CIV signal level required to drive the 781 properly - perhaps you
>know the answer to that?
>
>K8AC

Gary Fiber K8IZ
GROL PG-19-6691
Washington State Resident