Star Trek The Next Generation


Game did not want to boot at all.  The voltage at the MPU was only 4.6 volts and it was 4.8 volts at the driver board.  Both of these are too low for the game to boot. The first issue was the voltage drop between the two boards. On some of Williams more complicated games they added an extra connector to tap into the 5V and 12V power supply and they did this with a “Z” connector in between the two boards.  By removing this connector between the 2 boards and cleaning off the pins with a Scotchbrite pad the voltage on the MPU came up to 4.8Volts and the game booted. This voltage is still too low so a 22 ohm resistor was added between the ground and the voltage regulator and the voltage increased to 5.1V. 

Now that the game was booting the game was having trouble keeping track of the balls.  The first issue was the hole in the subway ramp under the game that was letting balls fall in the cabinet. This had been patched before with epoxy and tape and it came undone.  We placed an order for a new ramp that we will install on a return trip, but in the meantime re-epoxied the ramp.

Checking out the optos every single one worked in switch test,  The game would load all the balls into the correct locations and you could start a game. Everything appeared to play find until you locked ball 2,  then the game wouldn’t kick a ball out.  After a minute and 2 ball searches it would finally kick out a ball but report a pinball was missing, but once that ball drained it would clear the error as it had found all 6 balls.  Strange.  Pulled all of the popper and trough assemblies under the playfield and all optos worked, no cold solder joints, not bad or falling off resistors.  Finally looked at the ball trough for the shooter land and there was a subtle difference, the opto transmitter for ball #3 was dark purple instead of the yellow clear of the original otpos or light pink of the correct replacement optos.  Someone had replaced opto #3 with a Stern part instead of the correct williams part.  It worked in switch test and during most of gameplay but at some point when there was only 1 ball left in the trough it was failing and the game thought there was a ball stuck in the #3 spot in the trough or something like that. Replacing that transmitter with the correct opto fixed the problem and now the game  played 100% correctly.