Testing a 1488 line driver...

[Roy J. Tellason]

On Thursday 03 January 2008 20:43, Gene Buckle wrote:
> >> 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.
>
> I'm not sure I know how to do that.  I was just going to pull the
> converter and power it up by itself to see if I get -12v out of it.

That's exactly how you do that.  Just disconnect that output and see what's 
there.  If it gets close to what you could call normal,   then there's some 
other problem,  like a shorted bypass cap or similar.

I never used to see all that many problems with shorted caps,  but discussions 
on other lists (tek scopes particularly) seem to indicate that it's getting 
to be a common problem these days.

-- 
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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