Twilight Zone

In-Home Repair

Tucson, Arizona

Forgot to take pictures for this one.

Customer noticed the ball popper and a few other coils weren’t working so he found a bad fuse and replaced it and afterwards alot  of the controlled insert lighting was locked on solid and then they all stopped working  so he called in the pros.

The lamp matrix circuit is in the lower right corner of the driver board so we start our search there. The voltage for the lamp matrix is 18 volts even though the game uses 6 volt bulbs.  The game pulses this voltage so that on average each bulb only sees 1/3 of the full voltage otherwise the full 18 volts will burn out all the bulbs.

 There was 18 volts DC at the test point so the bridge, cap and fuse were OK.  There was voltage at both the row and column pins so everything in the rest of the circuit appeared OK.  Weird.  So that would most likely mean that somehow the voltage got stuck at 18 volts and burned out every light bulb,  checked a few bulbs and they all worked fine when I swapped them into a GI socket .  Stranger yet. 

That is when I noticed that the only light that was flashing on the pf was coming from the Robby the Robot Mod that was added to the game. It has 5 or 6 LED’s in it.  3 are driven from controlled lamp sockets and the rest are driven by 12 volts from the game.  the 3 driven by the controlled lamps weren’t lit but the others were flashing.  Removing the wires from the 3 controlled sockets didn’t change anything.  I followed the wires for the 12V and ground connection and they were installed inbetween the Z connector between the CPU and driver board.  Just touching this connector made the insert lights come back on!!!!!

This is where I really wish I had taken a picture.  The two wires for the robot mod had alligator clips on them.  The Z connector was pulled slightly apart and the alligator clips were clipped onto the exposed pins. (terrible place to locate these, but this is how the kit instructions were written )  One of them must have been shorting to the other pins and causing a problem. now the only 3 lines on this connector are 12V, 5V and ground.  I am not sure how shorting the 12 V to 5V or ground would disable the controlled lamps.  Disturbing the 5V would probably not allow the game to boot. Shorting the 12V would cause all of the optos to go dead thus causing a switch matrix issue and possibly causing quite a few solenoids to fire at once and pop a fuse (which may explain the owners first issue). 

So we had to find a new place for the 12 V and ground wire for the robby mod to live.  We removed both alligator clips and soldered the 12V wire onto the test lug and the ground wire to the ground plain on the corner of the driver board so that they could not fall off or short again.  These are still easily removable later if need be, but are less likely to fall off and cause any shorting issues again.