Re: Lisa 2/5 I/O board troubleshooting.

Trace repaired... system works!

[image: Inline image 1]

However the parallel port does not. After some investigation I found the pins are snapped off inside the connector! A new one is in the mail, so I should have a mostly working system soon.

Thanks,

-J

On Thu, Oct 26, 2017 at 12:37 AM, compu_85 <perkins.jason_at_email.domain.hidden> wrote:

> Sorry, I had a typo in the last post. I meant to say the power on signal
> on pin 24.
>
> The power switch signal on pin 20 is working properly... 5V when the
> button is not pressed, nearly 0v when pressed.
>
> On the bad board, I found that pin 14 of the COP is low when the system is
> turned off, 0.5v. On the working board this pin is ~3v when the system is
> off, 0.5v when the system is on, and 5v when the power state is changing
> (powering on or off). This pin is supplied power by 1K resistor R46 form
> the 5v standby rail, and is pulled low by pin 39 on the keyboard 6552 pin
> 39.
>
> If I remove the 6552 the system powers up with the bad card! So getting
> closer...
>
> With the system plugged in both sides of R46 show 5v... suspicious. Sure
> enough, the trace on the output side of R46 is broken. Fixing that will be
> tomorrow's project.
>
> -J
>
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-- 
Jason Perkins
313 355 0085

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