Re: Asteroids DAC question

-----Original Message-----
From: Scott Brasington <arcade@brasington.org>
To: vectorlist@vectorlist.org
Date: Fri, 09 Sep 2005 19:18:29 -0400
Subject: VECTOR: Asteroids DAC question

>
> 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?
>
> If a DAC is bad will get you any video, or just a line or ??
>
> I got some boards I'm trying to repair and before I go swapping
> out an expensive chip I'd like to make sure there is a high chance
> of probability that the chip needs to be replaced.
>

i would start by metering the reference voltages, and probing the digital inputs.
if the references are good and you have all the databits moving then check the output.
if you have any at all then replace the output amplifiers & stuff.
only after all these things should you suspect the dac.

another method is to socket both dacs and swap them - if the fault changes it's a dac, if not then it's something else.

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Received on Fri Sep 9 23:37:43 2005