All my switched lamps have stopped working.  I have checked the lamp driver board for voltage, getting 5VDC at TP1. Any ideas as to what this could be?  I was in the process of changing dip 16 from 3 ball to 5 ball when it happened.

I assume this is for a late 70s or early 80s Bally ?

If so, check the Controlled lamps fuse and the associated bridge rectifier on the rectifier board.

The +5V measure at TP1 on the lamp driver proves that the +5V regulated output from the
solenoid driver, feeding the +5V to the MPU, lamp driver & displays, is good.

The controlled lamp voltage supply has its own separate circuit, bridge rectifier and fuse, and
is not related to this +5V.

One more note: it is recommended to change the DIP switch settings on these MPUs only
with the machine turned off. The DIP switch new positions are read upon the MPU booting.

Cheers,
- Sylvain.

Thanks Sylvain

It was the fuse. It's working great now.