OK.. CPU isnt booting.. its trying hard to though.
The logic voltage on Zacs is a little higher than normal, but all the IC's are well within range and youll find that the voltage drops as it fans out through the board.
The RAMs are right in the corrosion zone.. the pads will be the main issue IF it is corosion that is the problem here.. we havent determined that yet.
The 2 RAms are a bugger of a job... pulling off a socket will do some damage to what could be a delicate area.. this will need to be repaired.
The cct between the 2 RAMs i didnt enjoy rebuilding, but in all honesty it took maybe 2 hrs tops
R1, D1 and D2 cop a flogging with corrosion too.
Theres a large ground path at battery -ve.. mine was eaten away and all R2 - R9 had floating pads... check all this.. buzz it out well, its all one of those jobs that you dont want to have to go back to.
In all honesty, your CPU was booting - now its not, but it is continually trying, not just locked off..
Have you checked all signals on the 2650 CPU?.. This can give very big clues as to why its not booting.
Check that you have signals on data bus on 2650.. anything missing and strongly suspect broken traces or socket fault on Eprom to CPU.
A logic probe is excellent for zac games.. apply to pin 10 IC5 ( 2114 RAM).. make sure its pulsing... then CPU pin 23.. same signal.. should be pulsing.
Id say.. do all this on the bench.. the board seems happier there
Still no joy with this board. The board is booting every time according to the LED, which is on constant.
None of the cabinet switches do anything.
Switch 4 on the cpu board turned to the on position makes the machine make a constant noise, but the advance test button does nothing.
I have replaced IC5 IC8 IC17 IC19 IC20 IC33 IC38 and IC41, this has made no difference.
I have tested the Data bus and the Address bus, everything seems to be ok, i dont have a logic probe only a DMM.
The score displays are on zero and the credit display alternates between 4000000 and two zeros on the left and one zero on the right.
The PF lights are in there attract pattern.
So basically it looks like it should work but i cant get into the test program mode.
if any one has any suggestions please, i need help with this one.
Ian
edit: added youtube vid of machine with switch 4 on
