LOTR KNOCKER
(or other modern Stern)

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This started as a blacklash to sellers charging up to $100 for kits that added a knocker and a few other bits to a modern Stern game.
There are great instructions showing how to make a Stern Knocker with all standard Stern/DE parts
found here. Parts can be ordered from www.pinballlife.com, and these are the part numbers you need:

• Knocker Strike Plate: sp01
• Data East/Sega Knocker: 500-5081-00
• Stern 50-Volt Step-Up Driver PCB: 520-5254-00

Cost is currently $26.70 plus shipping as of Feb 2010.
(Not counting the connectors & some 20 guage wire which you need to source)

On my game, I used a 6v relay instead of buying the extra Stern 50-Volt Step-Up (520-5254-00) circuit board.
The pull-in was fine at +5v DC, and everyone should be able to source a relay, a diode and some wires in the future.
I used a knocker assembly (bracket and coil) taken from a Blackout cabinet and had the 6v relay in my spares.
My coil is a Williams SA-2-23-850 DC but any 23-800 or 23-850 DC will work and be loud enough.

Notes:

• Both my Black Knight 2000 and Twilight Zone have the knocker mounted in the head
  -but maybe not on DE/Sterns. I put mine up top where it's louder than the other game coils under the playfield.


• My opinion is that's would be best DIY place for it. It's up to you how you do it.


• I put an inline fuse holder with a 4A SB fuse in it between +50v and the coil lug.


• Ground point for the coil was a backbox screw holding the metal sheet that boards are mounted on.


• Set game to use your hardware knocker:


• Set #46 -Q24 option to "knocker" and turn #34 "software knocker" volume to off.


• On my LOTR LE those are the adjustment settings #'s from the Service Menu.



Set game to use the software knocker:

• Set Q24 option to: coin meter and the "software knocker" volume to LOW (50%) or NORMAL (100%) and you swap back to the software knocker.


• If you take the game off "free play" then you will hear the hardware knocker on this settting if you insert coins.




• So you can swap between them as you like. Maybe at a loud party the "software knocker" at NORMAL would be best.



• Test the knocker on the "optional Q24 coil test" by firing that coil (well you can on my LOTR version).
But the sound isn't as loud on test as when you hear it in a game, so maybe the coil pulse is shorter when on test?


• The "knocker test" on the menu can only test the software knocker.



• Here's a youtube video of me testing my knocker to prove it would work.


• I later found that Leon (he of the Test ROMs) had published the same relay mod as I made. Great minds think alike.
  He put a 0.1uF cap (50v) across the relay contacts, not a bad idea to save the life of the relay.
  

Here is the circuit diagram and pinouts for a SAM I/O driver board which was on my LOTR LE
(check your manual to see if they are the right pins on your game).

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