Thanks for help guys,

Yep, slam mod done

MM,

No playfield attached at present.  Just backboard and power section.  AFAIK this is fine, power supply rebuilt and connected to CPU.  Without displays attached (shouldn't matter) can still monitor if CPU booting by probe on pin 4 U1.

Clock seems to be fine.  On my cheapo logic probe, I'm getting 1 (high) 0 (low) and pulse all lit which I believe is pulse.  This is on Z3 pin 6 and U1, U4,U5,U6 pin 39.
U2/U3 are new.  I dont know where to read the clock on these and couldn't see on schematic.

From the pinrepair guide, the clock looks to be OK, same as RDY and Reset.  Something is holding the IRQ high.  I have not touched or looked at Z9/Z10 or Z7/Z8.  These are about the only ones I havn't replaced.  From the schematics (Z9) there should only be activity on 4,5,6,7 & 14 (gnd).