[Kenwood] Another TS940 problem. Auto ATU this time.

[Traian]

Hello Martin,

I had a similar problem for a TD570D Tx command line, some years ago,
when I also posted a message about.
While pulling up the line may help sometimes (you may try), it did not work
for
that TS570D microprocessor port line. Only for a very low pull up R value
(2k or lower) the line was going close enough to VDD, but even then it
couldn't
switch back to GND, of course.

The only solution was to replace the CPU IC which solved the problem.


Good luck,
Greetings from Bucharest,
73,
Traian



Martin Sole wrote:

> Hi,
>
> Well I got this particularly abused TS940 all fixed and it's been
> sitting on the shack floor for a month or two waiting for the owner to
> come calling. He finally did and I showed him how his radio was now
> working great. Right up until I tried the auto ATU. Selecting Auto/Thru
> sets everything up right, the relay closes etc. Pushing AT.T does
> nothing. Looking at where this comes from, the dreaded digital A board,
> I see it outputs from 1 bit of a port expander. Pin 20 of IC6. With this
> line disconnected from the auto ATU board I see only 2.5 volts on it,
> not the 4.8 I see on another one, also see about 24K between pin 20 and
> 19, a good one shows infinite.
>
> Does it seem likely that the port expander has died? I can still see the
> trigger pulse on the line and was wondering if I could arrange some sort
> of extra pull up to force this line high so that the pulse would
> properly trigger the following monostable.
>
> Any ideas?
>
> 73
> Martin, HS0ZED G4UQF
>
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>
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