Lamps/Lights Don't Work

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Case Study Summary
Game Lido
Games Applicable To Almost all games
Source phil
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.
Fix confirmed



The card number lamps share the circuitry with the search relays.

Apparently 6V wouldn't be enough to operate the search relays reliably (assuming you used a 6V coil), so the lamps need to survive in the higher 17V environment. That's why 1458 or 1464 lamps are used instead of the 55 or 47's.

Many 6-card games took a different approach...they put three 6V lamps in series on the 17V circuit - the downside is when you lose a lamp, the number goes out on three cards since the two remaining good lamps are in an open circuit.

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.


Lamp power rail source on Lido

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'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.