This board splits the signals of any of the Solenoid coils into individual fusible circuits.
Where the Special Solenoid Saver is exclusive for those coils, this version can be used with any circuit with the 9-pin Molex .156 header. Can work with Williams, Data East, Sega, Stern, or any other machine with that header type. Simply clip the key pin and don’t bother to populate the corresponding fuse.
in the example above, I am adding this board to a Data East TMNT which just had a 74xx fail.
The special solenoids are protected by a single, 4A SB fuse. In the event of a stuck switch, that corresponding solenoid will lock on, until such time the switch becomes unstuck, or the fuse blows - whichever comes first. Unfortunately, the coil will heat up and melt the inner windings of the coil, and lower the resistance to the point that the corresponding transistor will get cooked and dead shorted. All before the amperage reaches that 4 amp threshold, and finally blows the fuse. So, you will need to replace the coil, the TIP and any other components that were over-stressed. All for a simple stuck switch.
With this mod, every coil is given it's own fuse. My suggestion is 1.25A SB, though 1A usually works, and 1.5 is probably OK. In the event of a stuck switch (or shorted TIP), the lighter fuse will blow much sooner, saving your components.
This version does include an indicator LED on every line, so a failed fuse can quickly be identified.
