MPU reel drivers

[Nepa Coin Op]

I have 2 machines here giving headaches, let me give a quick overview ......both are quick n easy machines..... one was playing started acting up other was like this since 1st power up......... both on boot up when they test spin the reels when getting to the 3rd reel it will act up... #3 reel will studder or not spin like it should then give a 3 reel spin error....


first i though it was dirty optics on reel 3 I cleaned them with no change
then I thought it may be a bad stepper on #3 so I swapped the ribbon cable from 3 to 2 and the problem follows the cable change.
both machines experience similar probs with reel 3 but not exactly so I took the board from mach 2 and put it in 1 to see if the prob is exactly same which would point to the cabinet wiring not the board but the prob follows with the boards so this prob is defiantly on the MPUs...in the output section of the mpus theres a drive transistor for each reel and an sla chip for each that controls the stepper.....in circuit they test ok which I have seen misleading in the past but before I go any further I would like insight from someone who may have ran into this.....it actually is acting like a leaky transistor or step controller. almost like the motor dont know what direction to spin in......does anyone know which IC controls which reel ?? I suppose I can swap the 2 outer ones and see if my prob moves to reel 1 but would rather only remove components 1 time...
any info is appreciated


Thanks