Black Hole

BH ball lift kicker mod

This modification developed by Steve Charland.

From an engineering standpoint, the upkicker for BH is a simple and direct design but it does have it's faults. The first being that there is no way to adjust the power of the "kick" from the lower playfield to the upper playfield. The second is the problem of the ball lift coil getting fried. This happens all too often due to shorted transistors, or failing transistors that provide "trickle" power to the coil, heating it up over time and eventually causing it to short.

The solution(s)

I'll address the first problem. I wanted to be able to control the speed that the ball would travel up the tube. The simple solution is to add an end of stroke switch and use a flipper coil. Since the switch can be adjusted to open at various "throw" points of the coil plunger, you can control the force of the plunger strike to the ball. Open the switch early and the ball travel will be slower. Open the switch later and the ball travel is faster. Making the end of stroke switch bracket isn't too difficult to do. Contact Cliffy and hopefully he'll have them for sale soon.

Now...on to the A-4893 coil getting fried. There is something to note here. The schematic calls for a 6 1/4 amp Slo-Blo fuse for F17. A 6 1/4 amp Slo-Blo passes way too much current to protect the ball lift coil should either the pre-drive transistor or the under-playfield drive transistor short on. No wonder it cooks so often. This coil needs to be protected with a 2.5 amp Slo-Blo fuse, just like the pop bumper coils (so the fuse blows before the coil cooks).

For this mod, I used a A-20095 flipper coil instead of the stock coil, and an end of stroke switch to turn off the power-stroke winding of the flipper coil. By using an end of stroke switch, if either drive transistors short on, only the hold portion of the flipper coil will be energized, in exactly the same way as a flipper operates.

• Black Hole Upkicker Modification.
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  Measuring for hole placement on the new bracket.
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  Trial fitting some sheet steel to the new holes. This sheet steel will eventually become the EOS bracket.
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  The new bracket and switch.
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  Another view of the new bracket and switch.
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  The bracket and switch in place.
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  Completed work, flipper coil installed.