Woodridge, IL
I thought this little project would be of interest to other Centaur owners who might also be suffering from magnet envy.
My Centaur was already missing the magnet when I bought it and I always wanted to put it back. Unfortunately, as we all know, a direct replacement magnet is simply no longer available. The Williams 20-9247 magnet IS readily available and looks and mounts the same way, but the coil is rated quite a bit differently and it cannot be used as a direct replacement. Undaunted, I decided to research how other games drive this particular magnet to see if a workaround might be possible.
I came across the schematic for the High Power Solenoid Circuit in TZ and realized that this circuit was functionally similar to the one in Centaur, at least up to the TIP102 transistor. Whereas Centaur uses the TIP102 to switch the magnet directly, TZ uses the TIP102 to drive a TIP36C power transistor, which in turn switches the magnet. It appeared that the answer might be as simple as adding a few extra components to the Centaur magnet circuit, so I decided to give it a try.
The modified control circuit works like a charm.
Installation is not difficult, but you do need to run a couple of extra wires. The first one is for a new 43v source. I tapped the brown wire at the 1A SB fuse holder for this line. The other is for a new direct connection to ground. I tapped the black/white wire near the Aux. Driver board for this one. Both of these new wires were then neatly run along the wiring harness down towards the magnet area. The third input is the gray/red wire from the original magnet circuit. At least this one is already in the right spot. I installed the additional electronic components on a small piece of stripboard and mounted it to the playfield near the end of the ball launch ramp and connected everything with a couple of molex plugs.
I also added a separate fuse for this circuit. TZ protects its circuit with a 3A SB fuse, but the voltage in Centaur is a little lower and I found that a 2.5A SB is sufficient. I put the fuse holder near the existing one for the 1A SB fuse.
Hopefully the following images help clarify what’s involved.
Zemst
