Why is the search index coil burned out?
Games affected: games between Sea Island and Bounty
The search index coil stops the search wipers when a winner is detected and holds the wiper contacts on the winner while payout is happening. This coil is the most commonly burned out coil in a bingo, and the reason is due to a design flaw.
Like all high power coils, it is not intended to stay powered on for a long period of time. Obviously it needs to be powered for the amount of time needed to complete the maximum payout, and it can handle that, but when it gets stuck on, the coil will get red hot, burning the paper wrapper and eventually the coil wire.
The sequence of operations is supposed to be:
- winner is detected
- search index coil is activated, holding search wipers on winner
- replay cams are released and the control unit motor turns them. The replay cams provide pulses to the replay counters and replay registers to award credits
- replay counter reaches payout level, and cuts off power to the search index coil and replay cams index coil.
Sea Island Schem
|Timer unit switch shuts off motors|
Starting on Sea Island, Bally decided to reduce wear and tear on the mechanisms by shutting down the moving parts shortly after the fifth ball is shot. The timer unit accomplishes this when it reaches it's top step (8th).
The switch at the top of the orange line is normally closed, and powers
the motors through the tilt trip switch. If the game tilts, or the timer unit
reaches it's top step, the motors stop.
So, it would be a bad idea for the motors to stop during payout. The obvious way to stop this from happening is to make sure the timer unit can't step up while payout is occuring. Let's see what Bally did.
Sea Island Schem
|Timer unit stepup circuit|
The addition of CU14B makes it less likely for the timer unit to step up, as you need three things to happen at the same time instead of two, but it's still possible for a pulse to sneak through.
So it becomes an intermittent race condition. If you happen to push the 'R' button to start the payout when CU1A is closed, then CU1A and CU14B will open/close together. When all three switches close enough times, the timer unit steps up and the motors shut off while the search index coil is still powered. You'll need a larger payout for this to happen.
If the player is standing at the machine and it shuts down while payout is happening, pushing the 'R' button resets the timer unit, the motors start again, and payout continues. If the player walks away....trouble!
On Bounty, Bally added another path on the motor power circuit which went through a switch on the replay cams index unit. This circuit kept power on the motors while the replay cams index coil was powered, but had the disadvantage of adding another 120V circuit to the game.
At some point after Bounty, probably on Border Beauty, Bally decided the extra
120V circuit was daft, and they just moved the CU14B switch to the replay cams
index unit, which effectively stops the timer unit stepup while payout is
Possible FixesThere are a few things you can do to fix this problem:
- do nothing...just don't leave the game if you get a big payout until the
- if you have the spare parts, add another switch on the replay cams index
unit and move the two wires from CU14B to it. The switch should be adjusted
to close only when the replay cams are locked.
- disable CU 1A by bending up the switch blade so it can't ever close. Doing this
means the timer unit never steps up far enough to turn off the motors, so
if you leave the game on when not playing, this is not a good option.
- and another fix from alan (who has machines
for sale): Add an extra switch to the stack at the search wiper
(where the feed ring & R button index coil are located) use the 110v circuit
for the control motor, thus not allowing the control motor to stop running
unless the search wiper is back to Zero position.
- Jeffrey Lawton recommends moving switch 1A wires over to a new switch on the search
wiper stack (if the game has one). See
Jeffrey's writeup of this problem. This
is maybe better than alan's soluton, as it does not require an
extra 110V switched circuit.
- An operator in Reno probably did the most thorough solution. He added an extra relay to the game and ran 14B and all the switches currently on the search index unit through the switches on the new relay. He removed all the switches from the search index unit except on, which was used to close the new relay. This helped prevent the fibre tab on the search index unit that was lifting all the switches from bending/breaking due to having to lift up multiple sets of switches.