If you plan on repairing your own boards this a great tool and cheap to buy.
I asked you to test it, not replace it. They way you described your problem I would have checked U-56 pins 5 and 6. If that checked good I would have checked U-50 pins 8-13. One of these was your problem.
I don't know I have never read it, I'm just going by the factory schematics in front of me. There are 4 pages just for the CPU and if you look on page 1 lower right corner you will see U-56 sending a signal to both the flippers and the special solenoids.
Quoted from GRUMPY:
There still is a problem, but you may have caused it by installing a bad U-50 chip.
U-50 is a nor chip that has four logic gates in it and the board uses all four. When using an unknown old chip you don't know if it 100% without testing it. Lets say the original U-50 had a bad output on pin 13 causing all of the special solenoids and the flippers to not work. Then you replaced it with a used chip with pins 1 and 4 bad, now your flippers work and special solenoids 1-4 work but 5-6 are locked on blowing fuses.
Since they are socketed you need to inspect the previous work done on U-50 and may as well just replace the chips with new as these are inexpensive.