Installing a Real knocker in a Stern SAM machine
(WPT, POTC, FG, Spidey…)
Background:
The SAM system hardware and software were designed to accept an optional knocker using Q24. Unfortunately Q24 is a 20 volt channel and not a 50 volt channel. 20 volts is not enough to produce a really loud crack, so a conversion board is needed.
We’ll use Stern‘s new 50 volt step-up board - first introduced in WPT. The SAM board set doesn’t have enough 50 volt coil drivers for all the 50v coils in WPT. If you look under the playfield there is a tiny surface mount board that converts a 20v channel into a 50v channel. This board is exactly what we need to make a loud knocker. It was designed along with the SAM system, so its not a kludge.
Parts:
- Wire (~16 gauge), molex connectors and contacts
- Knocker assembly (Data East/Sega #500-5081-00.)
(
http://www.pinballlife.com/index.php?p=product&id=675&parent=0)- knocker strike plate - SP01
- Stern step-up driver board part number 520-5254-00
Installation:
You will need to connect to the following existing voltages and signals in the cabinet:
50 volt coil voltage: 50 volts is available on many coils under the playfield. You can make a plug-in adapter or just solder onto a convenient coil lug and snake the wire along with the harness back to the knocker.
Ground: Black wire found many places in the cabinet - including the tilt plumb bob switch
Q24 driver: This violet/gray wire comes from Q24 on the driver board and is used to control ticket dispensers or knockers. You can find this wire in a small, unused white connector inside the cabinet; in the area of the coin door and tilt assembly. The red wire in this connector won’t be used.
Mount the knocker assembly and strike plate in the cabinet. Make sure the plunger can make almost a full stroke. Be sure to remove the diode from the coil.
Mount the step up driver PCB near the knocker and wire it all up.
Once everything is wired up and in place, you just need to make a couple of changes in the menus. Select “knocker” in the Q24 options. Turn the software knocker volume to “off”.
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Notes/bugs:
- The knocker diagnostic unfortunately tests the speaker knocker, so there is no way to test the knocker.
- The knocker will not crack if an extra ball is awarded instead of a credit.
Hopefully Stern can modify the basic SAM software to better support the optional knocker.