Six-Trak repair help needed.

[Hallgeir Helland]

Duane R Balvage wrote:
> 
> > I suspected the MUX associated with the DAC but replacing didn't
> > improve the situation. The DAC btw outputs what I'd excpect it
> > to. (but those strange envelopes appear there, too.)
> 
>   Yep. Sounds like a stuck data bit somewhere. Check for any stuck
>   bits at the CPU first w/ a logic probe.

I just built a logic probe (TomG's design) and did what you said.
It seems as if all the data lines are OK - meaning they go both 
high and low. And all the bits between the DAC Latches and the
DAC measure fine. So I suspect the DAC itself.

Is it likely that the DAC loses a bit?
It's a 7541 four-quadrant kinda DAC... 18 pins...
sould I get a new one (about $18 around here)?
Ought I put it in a socket? (a good socket of course.)

Any help is always deeply appreciated.
This is btw my first "difficult" repair job.... :-)

thanks,
Hallgeir
-- 
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 Hallgeir Helland   hhelland at mailandnews.com     
    Evlogia           http://fly.to/evlogia
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