Re: lisa 2 startup problems

yes. good luck with the diagnosis Alex. I was fortunate enough to get THREE Lisa's as a job lot. None were going at the time but I had the ability to mix and match boards. In the end I get two of them going (the third is missing a video card). Having a working board for comparison certainly makes things easier!

Terry (Tez)

On Fri, Nov 2, 2012 at 12:27 PM, James MacPhail <gg__at_email.domain.hidden>wrote:

>
> Welcome to LisaList Alex,
>
> Others may have other suggestions, but here are my thoughts:
>
> In general, if you have had battery corrosion and the Lisa won't power up
> when you push the button, there may be a bad trace on the I/O board (these
> two things often go together). Double check that area and test the
> continuity of the traces and vias as well as making a visual inspection.
>
> More specifically:
>
> If you've found the power switch signal is reaching the COP421 at pin 20,
> but it isn't turning on the power: check the COP has power (pin 9 should be
> approx. 5V), and check it is not held reset (pin 4 not below 2.5V), and
> that pin 1 is truly connected to ground.
>
> If you have a moderately high impedance probe, check the COP oscillator is
> running (approx. 3.9 MHz at pins 2,3). If not, check the parts/circuit
> connected to pins 2 & 3.
>
> If it all looks good, and the COP oscillator isn't running or pin 24 still
> refuses to switch, then the COP might be bad, but triple-check it is making
> good contact in the socket.
>
> Note that the COP will only turn on the power... if the power is already
> on, the power switch won't turn off the power unless the 68K CPU is running
> and executing some software that is watching for the power switch.
>
> After getting the COP turning on the power, I'd start working on the CPU
> problem... horizontal bands on the screen is typical when the Lisa is not
> running well enough to start the memory test. I may seem like a broken
> record/skipping CD, but I'd first check/clean the card-edge connectors for
> the CPU, I/O, and memory boards.
>
> Good luck!
>
> James
>
> ... it won't start. The motherboard was badly corroded but I cleaned the
>> corrosion
>> ...
>> ... on the COP421 chip I can measure the power button signal when I press
>> the power button but the state of pin 24 remains the same
>>
>
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