Testing a 1488 line driver...

[Roy J. Tellason]

On Wednesday 02 January 2008 22:50, Gene Buckle wrote:
> > 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?
>
> I actually used a little light bar I have that has 3 12V LED assemblies on
> it.  I ended up using this after my resistor decade box died on me and I
> couldn't find a 500 Ohm resistor. :)

Why I salvage all sorts of parts...

> >> 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.
>
> I've got one of those as well - it never shows a state change.  I tried
> that first.

Well,  there ya go then.

> > 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.
>
> I did check the power first. :)  12V like it's supposed to be.  If I have
> to pull the board, I'll certainly put in a socket. :)

Both plus and minus 12V?  You do need both.

If there's no change in the LED indicator,  and the input that drives it is 
changing,  then yeah,  it's probably toast.

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