Testing a 1488 line driver...

[Mr Ian Primus]

--- "Roy J. Tellason" <rtellason at verizon.net> wrote:

> On Thursday 03 January 2008 00:48, Gene Buckle
> wrote:
> > > I didn't check for -12V. I'll do that before I
> go to the effort of
> > > pulling the chip and replacing it.
> >
> > Checked it.  -0.60v  There's a Elpac/TDC CB-3811
> DC-DC converter on the
> > board that may have died.  I'll pull the board
> tomorrow and test right at
> > the legs of the device.  Thanks for questioning
> whether or not I'd checked
> > the -12v supply!
> >
> > Finding a replacement is gonna be a stone b*tch I
> think. :(
> > I may have to go to another DC-DC converter that
> is near the same size
> > that I can wire in.
> 
> Something might be loading it down, too.  I'd check
> for that before assuming 
> it's bad.

Yeah, like maybe a shorted 1488 :)

See what else uses -12v, and work from there. For what
it's worth, I've replaced quite a few 1488/1489's -
they typically get zapped in terminals when people do
stupid things with the serial lines while the terminal
is plugged in. I don't know if a failed one can short
out the -12v rail though. Never seen it happen
specifically, but that doesn't mean it can't.

-Ian