Lamps/6 card lights out

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Case Study Summary
Game Nashville
Games Applicable To 6 card machines
Source terry
Problem Reported #10 doesn't light on any card
Fix unconfirmed


The card number lamps are on the 17V power circuit, but in the 6-card games, 6V #55 or #47 lamps are used. Putting 17V on a 6V lamp would result in a very bright light that lasted a second or two before the filament vaporized like a fuse.

So 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.

Usually the problem with the card numbers are either:

  • all of them are off, which is caused by the entire 17V disappearing due to a bad fuse or an open switch in the anti-cheat relay or tilt trip relay
  • a number is off in cards 1-3 or 4-6 and you get to find which lamp has burned out or has a bad socket.

The more unusual case is a number is out on all 6 cards, but the rest of the numbers work. That's the case we have here.


Lamp circuit on Nashville

The schem shows the 17V transformer winding and the 17V circuits on the right side. Only lamps for hole #1 and #10 are shown. The circuit itself is pretty simple. Assuming the game has been cycled once after power-on so the anti-cheat relay switch is closed, and the game is not tilted, the 17V power is supplied to one side of the lamps on the red wire #10.

To complete the circuit and light the lamps, we need to complete the path from red wire #10 through the lamps to yellow wire #30. The only thing needed is the playfield hole switch to close.

If you haven't read electricity,voltmeters and reading a schematic (or it made no sense), and you aren't familiar with electricity or schematics, think of the schematic like a road map. You need to start at the transformer and walk along a path that goes through the thing you want powered - in this case the lamps - and get back to the transformer without getting blocked by an open switch.

In our problem, there's three switches that could be open, but since the rest of the card lamps work, the two supplying power to red wire #10 and the fuse is ok, so either the playfield hole switch is bad, or there is a broken wire someplace in the hole #10 circuit on the yellow side of the lamps.

There is one other gotcha that is never shown on the schematic. Since the playfield is in the cabinet, and the lamps are in the head, there must be a plug connection in the circuit. On Nashville, Bally added a second plug connection on the lamp panel insert itself to simplify manufacturing. It's pretty common for these plug connections to deteriorate over the years, and a simple cleaning can fix all sorts of problems.

Inspection Debug Procedure

The first guess is the problem is one of the plugs. To avoid any effort, just clean them all. Since the 115V main power circuit goes through one of the plugs to get to the power switch under the cabinet, you don't want the game plugged into the wall when you start yanking plugs.

Unplug the machine from wall, grab a brown masonite plug and pull it out.

dirty plug pins

Clean off the black stuff - a green scrub pad works if you don't have a wire brush or really fine emery cloth.

Squeeze the socket to bend in the tabs on the outer sides a little. This will make the socket clamp the plug pins harder to make a better connection and also scrape the surfaces clean when the plug is inserted.

Do this to all the plugs and see if the problem is fixed.

Next up is to eliminate a dirty playfield hole switch as a possible problem. With the game power on, just use your finger to close/wiggle the hole switch and see if the numbers light. If they don't, you can either use a voltmeter or a jumper wire to find the trouble, but you're going to need to know where the stuff shown on the schematic is physically located in the machine.

The playfield hole switch is obvious and inconvenient since most likely the switch you want to get at is underneath the shutter panel. You can remove a few brackets and flip the shutter panel away from the playfield without disconnecting it from the motor, but that's a hassle and it's not likely to be the trouble. What you really want to know is where the plug connections are, and most schematics have a plug chart to show you.

First you look at the schem and note that playfield hole #10 switch connects the lamps on wire #31-1, so look for 31-1 on the plug diagrams.

Nashville Plug Chart on Schematic

In this case, there's two plugs the wire is going through. The standard one between the playfield and head which I labeled plug B, and the extra plug on the lamp panel which I labeled plug A. The plug chart perspective is looking at the wire side of the inserted plug with the wire bundle on the bottom. 'course, where are the plugs?

Nashville - inside the head

The plugs between the cabinet/playfield and the head are always at the bottom of the head, and the plugs are grouped together. All the plugs from the playfield are adjacent, so you can usually figure out just by looking at the plugs which is which based on number of pins in the plug, the relative sizes of the plugs, and if necessary, the wire colors or pins with no wires on them. In this case, the 24 pin plug B with wire #31-1 coming from the playfield is the leftmost one, and wire #31-1 itself would be the 6th wire up from the bottom on the left side of the plug. With a bit of luck, you'd be able to tell it's a yellow/red wire.

Plug A on the lamp panel is mounted sideways, so wire #31-1 is the 4th from the left on the top row of pins.

Voltmeter Debug Procedure

You want one voltmeter probe on wire #10. This is the main power line from the transformer and is attached to one side of all the card lamps. Usually this will be manufactured as a bare wire daisy-chaining between the card sockets, and somewhere red wire #10 attaches to the bare wire.

Plop a ball in hole #10 to close the switch, and then use the other meter probe at points in the circuit looking for where the 17V meter reading disappears. The obvious and relatively easy places to stick the probe is where the wires attach to the plugs.

Probing with a voltmeter

To insure you have the meter configured correctly (measuring AC voltage on the right range), you can probe directly onto wire #30. You can get at wire #30 on the transformer, or note that it's also tied to a lamp that is always on. In Nashville, the lamps lighting the game name are at the top of the panel and the wire is easy to get to, so that's a convenient place to probe as a test. If you don't get 17V on the meter, but some of the card lamps still work, you are doing something wrong.

If you do get 17V on the meter, leave one probe on the lamp socket/wire #10, and move the other one to wire #31-1 on plug B. If you get 17V, the playfield hole switch and wiring is good up to plug B and you can move the probe to plug A. If you don't get 17V on plug A, then the connection at plug B is bad (you can probe the wire on the socket part to check), or the wire itself from socket B to plug A is broken and you'll need to find out where. It's almost always at a clamp - the clamp has cut through the wire.

Jumper Wire Debug Procedure

Debugging with a jumper wire

This is one of those times when a jumper wire is handy. You don't even need a ball in hole #10. All you need to do is connect wire #30 to points in the yellow side of the circuit and see if the #10 lights come on.

In this case, hook one end of the jumper on wire #30 on the game name lamp string, and stick the other end of the jumper on the wire #31-1 on plugs A and B.

When using a jumper, you usually are touching points in the circuit close to the lamp you want to turn on and working your way further away until the lamp won't power. If touching the jumper to wire #31-1 on plug A lights the lamps, but touching to #31-1 on plug B doesn't, the problem is plug B or the wire between plug B and plug A.


not reported yet