Hopefully someone out there can get me out of a jam.  I have now entirely messed up the 6-digit displays of 3 of my Bally SS pins, apparently by interchanging solenoid boards.

The History:
Bought a Harlem Globetrotters that wouldn't boot past the 2nd flash.  Always wanted an Alltek MPU so I bought one and put it in.  The machine booted and played, but the displays are completely blank. Went through the Bally repair guide and followed the steps. The solenoid board shows 170VDC where it should and 230 VDC where it should...however, it seemed that I wasn't getting any volts on the J3-8 pin. I checked header pins, tried a little resoldering.  Nothing worked.

I swapped out the solenoid board with  the one from my 1978 Playboy which is the same board. The displays on my Harlem remained blank.  For "fun", I took the solenoid board out of my Supersonic and tried it in Harlem. Again, the displays remained blank.

Here's where it gets bad.

When I returned the solenoid boards to my Playboy and Supersonic, their displays stopped working !!!  The solenoids fire okay, but there just aren't any displays working. I am assuming some wacky voltage in my Harlem messed up the solenoid driver boards...but my knowledge of electronics is about a 1.5 out of 10.  

Can someone help steer me in the right direction.

My guess is you have a short in 1 or more of your displays and you're causing a fuse(F1 - 3/16A) to blow on the driver board.

Mike

Absolutely.  I thought I had checked that fuse, but in my frustration I forgot that I had only checked the rectifier fuse.  WHen I checked the 3/16 solenoid fuses, sure enough...they were all toast.  I will swap out the displays before putting in a new fuse.  Much thanks for your help !