The knocker assembly was taken from my old 1980's Williams Blackout game which I wanted to rebuild, so I needed the part back. Although it had worked in the LOTR LE, it wasn't pretty if you looked inside. It was also starting to arc the contacts in the relay, even though it was rated apparently at 5A and I had tied both of the N.O. contacts together which should in theory help. I also added a cap to try and reduce the arcing, but may have had used the wrong (too small) a value there. It was also running the coil at 50v+ DC instead of the 30v (or so) which that coil was expecting. So it was time to "re-visit" my mod, and "do it right" to match the quality of parts in the Stern game. I ordered these items from Pinball Life:
- Knocker Strike Plate: sp01
- Data East/Sega Knocker: 500-5081-00
- Stern 50-Volt Step-Up Driver PCB: 520-5254-00
Cost was under $30. (Not counting shipping charges or a 5 pin .156" connector and some wire, which I had).
- I fused the 50v DC supply taken from the I/O Power Driver board at 4A, using an inline (car radio type) fuse holder. The ground wire and the "Q24 knocker drive" wire run directly to the mini-board connector. I terminated those wires on the "I/O Power Driver" side using crimped tag loops. The other two wires are soldered directly to the coil lugs, with the coil diode removed.
- Instructions which are OK, but cover mounting the assembly in the cabinet bottom are found here. But don't use the plumb bob tilt bracket as a ground! I'll say that again later.
- Good points are: There is a connector for the Q24 knocker drive wire (or ticket despenser) already in the cabinet bottom, violet/grey. The wiring diagram shown is correct and can be used. It looks like a fairly tidy and functional install.
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- The bad points of the install are: I don't personally like having the knocker located in the cabinet bottom, where the bass speaker and the other solenoids are located. My ears are nearer the backbox. The knocker is also mounted on a block of wood to avoid the cabinet bevel, but even painted black it doesn't look right to me. And here's the killer:
- *** Warning *** If you locate the knocker in the cabinet bottom, DO NOT use the plumb bob tilt as a "ground source" as indicated in those instructions. It's not a dedicated switch on LOTR, and is in Column 7 of the switch matrix on LOTR. You will kill your game if you put 50v DC though the switch matrix! At the bare minimum you will blow transistor Q7, and who knows what else could get fried! Use a screw that fixes ground braid to the cabinet or runs to the legs and lockbar. That's definitely a good ground point. Test with power on that it is at ground. Don't assume any black wire is a ground.
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| Here you see the 50v mini-driver PCB on the bottom left of the backbox, above it the striker plate, the knocker assembly and then the fuse holder. I won't be adding the TOPs board, or whatever was meant for that location. |
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| The ground point is a screw at the bottom left of the metal plate for the I/O Driver PCB. The Q24 transistor has the knocker "drive wire" attached to the metal tab with a small nut and bolt. You can zoom in on the pictures (almost all in my blog are high resolution) for a better view. |
Oh and if you get done and a few things don't work (a couple flashers, some playfield lights) - don't start to panic, like I did. Check the ribbon cable that connects the CPU board to the I/O Power Driver Board. That's all it was. Turned off the power, reseated that cable at both ends and all was well again. Stern had even used "hot glue" to hold the ribbon cable in place for shipping, but I managed to knock it loose at the I/O Driver end. Bliss! An easy fix.
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