Cary, NC
Pinwiki has a good breakdown on this. Just went through this on a Bally Beat the Clock... 5.4 Lamp Problems
Like the prior game system, Bally 6803 games did not use a lamp matrix. All controlled lamps are turned on via SCRs (silicon controlled rectifiers, either 2N5060s or MCR-106s) on the MPU board. The SCRs on the MPU must be refreshed (turned on) at 60Hz since SCRs turn off when the AC sine wave passes through zero (called the zero cross).
The usual techniques for dealing with lamp problems should be employed.
Lamp always on
It's probable that the associated SCR is shorted on.
Lamp never on
Verify that the lamp is good by testing it in a working socket (like the backbox).
Verify that the lamp socket is good by jumping from a known good lamp socket to the suspect socket. If the lamp then lights, the socket and bulb are good.
Verify that the wire has not been severed by "buzzing" between the lamp socket and the associated lamp drive connector on the MPU.
Verify that the connector is working correctly by "buzzing" from the associated lamp drive SCR on the MPU to the lamp socket.
Test the SCR using the diode test.
Verify that the SCR is being turned on by the 4514.
Jumper it to another known working bulb in test mode. If it lights then the bulb and socket are likely good. Then trace if you have continuity to the driver board. If not check the connecter that plugs into the board. The press in wire connections are the worst and sometimes it can just be that. If you have continuity and it still does not work then it is likely the SCR. Sometimes the diode can be bad, if you have them at the socket, and usually you will have 2 lights messed up controlled by 1 SCR (phase A and B). But depends on what era game you have.
