Skateball

Next up for an overhaul is a Bally Skateball. From the beginning it seemed to be a quite easy job but while working at it, it turned out to be a quite tricky repair.

The CPU and solenoid driver board had been sent to a board repairer and should have been OK once returned but the owner couldn’t get it up and running and asked me to take a look at it. The CPU had been repaired for battery acid damage round the RAM memory area and did probably work once it was done, but now when it was back in the machine it didn’t boot properly. When starting the game the led first gave a short flicker and then flashed twice. This indicates that the RAM isn’t working properly. First fault I found was the backup accumulator which was completely discharged and with the power on it just read 1 V, so it is dead. Disconnecting it didn’t solve the problem, I still had the same two flashes. I took the RAM out of the board and run it in a tester, which gave me all errors and warning it could. So clearly the RAM chip also was bad. I ordered a new one and once it was in the socket the board booted properly.

Next problem was that I couldn’t get the playfield glass of, it was dead stuck. I had to use a suction cup lifter to get grip enough to slide it out.

 

Once the CPU booted there was no life in the solenoids at the playfield and the cause was two shorted transistors at the driver board and a fried coil at the eject saucer mechanism. Changing transistors, coil and a fuse solved it. Take a look at the screw to the left of the coil. It's not original and when looking at the top side of the playfield it has gone through and also forced the ball deflector upward causing damages at the playfield. Why not checking the length of the screw before using it?

 

 

When coming this far I was quite sure I had the electronics up and running. But when measuring the voltages from the PSU I found the high voltage to be 230 V instead of the regulated 190 V as it should be. The cause is two shorted 2N3440 transistors and a couple of faulty resistors causing the regulator transistor to be fully open. I have ordered the transistors and I am waiting for them to be able to repair the regulator. While measuring in the circuit the high voltage disappeared a couple of times and that was caused by a bad soldering at the base of the regulator transistor. I do not want to run the game with the 230 V high voltage since it might damage the displays. But before I turned it of the last time I started a game to check that it worked properly and found that no switches at the playfield are working. I’ll have to wait with the fault finding of this problem until I have got the high voltage circuitry to work properly.

While waiting for the components needed for the electronics I started to disassemble the playfield.

 

It is very dirty, that's no surprise, but a surprise was all different non original screws that had been used everywhere. It’s almost like the game has been parted out at some time and then been put back together again with what was available. One thing that wasn’t put back is the knocker, it’s still missing in the cabinet. I’ll try to find a replacement, the knock is essential when having a free play.