Lisa I/O error 54

[pgreffet]

Hi
At the end of the auto test following power on I have an error 54 on my I/O board.
I swapped this failing I/O board with a working on and the Lisa boots fine. So it is clearly a problem with the I/O board.
I swapped COP421 and the other chips mounted on a socket and still cannot solve the problem.
Il the Apple Lisa Handbook it says that error 54 means « Clock error ». So what could I check now ?
Thanks for your help.

 

[stepleton]

Do the mouse and keyboard work?

How are you with schematics?

The Lisa boot ROM talks to the COPS through VIA 1, U7C. There is a direct connection between the two. It sounds like you've swapped all the chips there are to swap. Perhaps then look at the connections between the COPS and the VIA on page two of this schematic and see if there is good continuity?

(Which model of Lisa is it? I'm assuming something other than a 2/10, but even if it is, the connections should be the same I think.)

 

[pgreffet]

Do the mouse and keyboard work?

How are you with schematics?

The Lisa boot ROM talks to the COPS through VIA 1, U7C. There is a direct connection between the two. It sounds like you've swapped all the chips there are to swap. Perhaps then look at the connections between the COPS and the VIA on page two of this schematic and see if there is good continuity?

(Which model of Lisa is it? I'm assuming something other than a 2/10, but even if it is, the connections should be the same I think.)

It is a Lisa 2/10. I am also looking for schematics of this IO board.

 

[stepleton]

It is a Lisa 2/10. I am also looking for schematics of this IO board.

Fire up your TIFF viewer: http://www.bitsavers.org/pdf/apple/lisa/hardware/Lisa_2_10_IO_Board/

Or view well-made but reverse-engineered (so maybe less reliable) schematics at https://lisaem.sunder.net/cgi-bin/bookview2.cgi?zoom=0?page=5?book=6?Go=Go