Twilight Zone (Bally 1993)

Twilight Zone is maybe the most highly valued game by pinball collectors, at least when talking about solid state games. It has more patents and stuff than any other game. Of course patents alone do not make a machine but Pat Lawlor really did fine job with this design.

My machine required a new display and some clock optos but is now working great, with very good playfield and cabinet. It would be hard to persuade me to sell this game!


Replaced the 12 hour opto on the clock. The clock uses special high gain optos, which are difficult to find. Luckily I had one. Also a new display is now in place. No more worrying about the worn display burning out the driver board.


Pullup resistors on Fliptronic board.

Changed the Fliptronic board opto input pullup resistors from 1k to 10k. Now I can use generic optos in flipper button board, and put the more sensitive optos from flipper buttons to the clock, if needed. The 4 new resistors can be seen in this picture, they are the ones with a light blue body between the light brown 1k resistors.


One of the Powerfield microswitches had its lever fallen off. No damage, I put the lever back and it is OK now.


I installed flashers to the GUM/BALL door panels, as they are in prototypes. Looks good!


The game was beginning to have difficulties in serving new ball to shooter. The ball release lever hinge point needed some cleaning and a drop of silicone oil.


I put some Teflon lubricant to clock and gumball gears. They operate very silently now.


Installed a switchon noise eliminator on the sound board. Game turns on and off with no annoying pops now.


Very warm weather in last weeks has brought a small problem in sight. When the game has warmed enough, it begins to reset spontaneously, usually when pushing the flipper buttons. This is a familiar problem in WPC games, and is often caused by a poorly cooled rectifier bridge beginning to fail. Also the driver board power input connector may have bad solder joints. Some day now I must remove the board and re-solder the connectors and change the rectifiers. I have plenty of time to that now, my summer vacation just started.


Well planned is halfway done. The rectifier change I planned last summer was forgotten as the tempereture get lower and the game stopped resetting. But now, there is again 27 C at shadow outside, maybe even a little more inside, and the old problem begins to appear again.

Driver board removed for fixing.

So it's just off with the driver board and on with the work. Not all connectors need to be removed, only those at the top of board. It is a good idea to mark the connectors with marker pen, so it is easier to put them back afterwards.

Driver board from solder side.

Looks like this board has been repaired before. But the BR2 rectifier soldering looks original.

A new rectifier waiting for installation.

Repair seems to be succesful! Inside thermometer shows 30 degrees C, but after one hour playing the game has not reset itself. And now, enough with the playing, it is time to turn game off so it doesn't heat the room any more hotter!


Also another rectifier, BR1 has started to suffer from old age. Controlled lamps brightness varies much depending on how many lamps are on. Checking the 18V voltage showed it is a bit low and changing. So it is time to replace BR1. That solved the problem, all lamps light steadily now.


Twilight Zone has been at my friend Taru's home since last autumn, while I've had her Elvira. We decided to permanently swap the games. No problems, since I still can go to a visit and play TZ if I want, and amazingly, the game has gotten into even better condition while on loan.