RE: Asteroids DAC question

I have an AD board that is down right now... the signal on one of the X
or Y lines, forget which since it's been months, is way too low. It was
something like -2v to +3v in range when I measured it with my cheap DMM.
 It's supposed to be +12v to -12v, right? IIRC, I picked up some DACs
and another IC that were the likely culprit but have been scared to try
the desoldering/resoldering required.

I guess my question is, should I try the other IC first? The plan was
to desolder and swap in a new one, installing SIP sockets in the
process.

Chad

----- Original Message Follows -----
> owner-vectorlist@vectorlist.org wrote:
> > Is there an easy way to know if the AD561J DAC(s) on an asteroids
> > (or similar type) board need to be replaced? Like is there a common
> > symptom of when they fail versus say something else in that same
> > circuit area?
> >
> > Do the DACs tend to completely fail, or partially fail?
> >
>
> Scott,
>
> On the Asteroids boards I've seen with bad DAC's ( 4 total, so I'm no
> expert) the video is still there but corrupt. And the corrupt video
> was "repeatably" corrupt: corrupt in the same area and in the same
> way. When put into test mode the grid was out of whack but the
> picture was clear and solid. Depending on which DAC was bad, the
> horizontal or vertical lines looked like dots. The diagonal lines
> look jagged.
>
>
>
> Sean McLachlan Salt Lake City, Utah
> rgvac@classi-find.net Video Game n00b since 2001
>
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Received on Mon Sep 12 10:57:47 2005