Williams The Getaway switch matrix

[PinPal]

Hi all,,
I have done this many times before, replaced globes on my pins allways with the power off.
But today I replaced a globe on the underside of one of the slings with the power on and   thinking I was not going to touch anything the game reset and I thought Hmmmm 
Now I got two switch row ground shorts on Row 3. and 4.
Kicking my self   
My qwestion is have I shorted the switch rows on U20 on the cpu ?


Pinpal.....

[Steevsee]

If you remove connector J209 on the CPU board, do the errors remain?

[PinPal]

Will try,
Pinpal..

[PinPal]

Removed J209 from the cpu, did switch test, no change.
Still has ground shorts switch rows 3. and 4. 


Pinpal...

[Steevsee]

This test basically shows that the fault is on the CPU board, and most likely U20 (ULN2803) as you surmised. 

Best to install a socket when you replace this chip, if one is not already in place.

[PinPal]

Thanks for that, have a couple of spare ULN2803 chips but this cpu is not socketed so will have to sent it away to have the socket put in.
Cheers
Pinpal...