Testing a 1488 line driver...

[Roy J. Tellason]

On Wednesday 02 January 2008 22:10, Gene Buckle wrote:
> I used an LED to watch the output on the 1488.

With an appropriate current-limiting resistor I would assume?

> The LED lights the instant I attach it to the output and doesn't flicker or
> go out when I reboot the computer to make it send data out the port.

The little tester I have for rs232 stuff uses bi-color LEDs,  makes it easier 
to see what's going on.

> The Port should be running at 9600 baud, so I should see at least some
> flicker activity on the LED if the 1488 is toggling the output pin.
>
> Before I spend the time to replace the 1488, I'd like to hear from you
> folks if the chip is actually bad.  Is what I'm seeing indicative of a
> dead 1488?

Could be,  I've certainly replaced my share of those.  And put sockets in 
while I was at it.  :-)   Just make sure it's getting the proper power 
supplies,  as if one or both of them are missing you won't see proper output 
then,  either.

Whenever you're trying to troubleshoot anything,  always verify the power 
supplies first!  I forget that myself from time to time,  and have regretted 
doing so.

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
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