Lamps/Lights Don't Work
|Case Study Summary|
|Games Applicable To||Almost all games|
|Problem Reported||score lights go out sometimes or do not light at all. Magic screen lights do not light or magic screen position lights when moving magic screen.|
The lamp circuits are pretty much the same on all the bingo machines. Usually the card number lamps run on a 17V circuit, and the rest of the lamps on multiple 6V circuits.
There are two cases where turning off most of the lamps is useful:
- when the game is first powered on but no coins have been played
- when the game is tilted
These cases are handled by disconnecting the power "rail" from the transformer. The rail is a common wire daisy-chained between all the lamps connected to that transformer lug through a couple switches and a fuse.
The schem shows the 17V transformer winding and the 6V tap poking out of it to the left on wire #51.
The first branch off wire #51 goes into what is mainly the general illumination string of lamps. GI lamps are always on - the playfield and some lamps behind the backglass. Another lamp lights when the coin door is opened, and in this game the "extra balls" panel on the backglass is always on when the extra ball #2 trip relay is tripped. These lamps work fine, so the transformer and GI string fuse/fuse clips are ok.
The other two branches of the 6V power rail are labelled "feature lamps" and "score lamps". That's what they mostly connect to, but to balance the current draw in the circuits, there are some feature lamps on the score branch.
Inspection Debug Procedure
When whole strings of lamps go out, it can only be one of:
- transformer - extremely rare
- fuse/fuse clips
- any switches in the power rail path
It this case, we know the transformer is ok, but we have a problem on a string that has the other two possibilities.
The most common problem is the anti-cheat relay switch (1). Because the anti-cheat powers on the first spin cycle and stays powered forever, the switch contacts on the relay blades don't open/close much, so they don't benefit from the contact face wiping motion that helps scrub off oxidation. Clean and adjust the switch blades on this relay.
The tilt trip relay switch (2) is much less of a problem because of the amount of bending the trip relay switch blades do. There's usually a lot of overtravel (blade keeps moving after contacts touch, so you get the wiping action). However, if the game isn't tilted much, the switch never changes state.
For the fuse, don't assume that just because the filament looks good the fuse is ok. Sometimes the filament breaks off at the cap end where you can't see it. In addition, poorly clamping fuse clips can create a bad connection. However, if the tilt light comes on when the game is first turned on, or when the game is tilted, the fuse and clips are ok.
Voltmeter Debug Procedure
This one is easy. One meter probe on fat yellow wire #30 (the solid black line along the bottom of the schem piece shown...it's usually the fat black line running across the middle of the complete schem), and use the other to probe the circuit through the fuse, tilt trip relay switch, and anti-cheat relay switch. The 6V will disappear someplace.
This time it was the tilt trip relay switch. Wire #54-2 wasn't making a good connection to #38 when the tilt trip relay was untripped.