Q*bert Knocker Circuit Overview
Gottlieb designed Q*bert to activate a knocker assembly when Q*bert
or Coily falls off the maze, which added the feel of the characters
hitting the bottom of the game cabinet. Pretty cool stuff!
Brad Oldham
has modified the MAME Gottlieb driver code to flash the NUM and CAPS
keyboard LEDs simultaneously to simulate when the original Q*bert game
activated a pinball knocker assembly. This opens up the possibility to
drive an actual pinball knocker assembly from the LED signals.
I found this modification to be a very simple add-on to my existing
I-Pac
I'm already using in my cabinet.
*** MAME Dev Team: Please add this function in the official
release code.
I modified my existing LED Driver Circuit
to incorporate a portion of the knocker circuit. I'm utilizing the unused Scroll Lock
input/outputs to drive my external knocker assembly. The remaining of the circuit is
on a separate schematic. See schematics below.
I based my knocker driver circuit directly from the Q*bert service schematics.
See below.
SW1 in the open position allows me to manually turn off the knocker
circuit. The switch is necessary to protect the solenoid if the
computer's CAPS lock is enabled during normal operation of the PC. If
not, the knocker solenoid would seriously overheat and blow the fuse.
Simply close SW1 when you want to play Q*bert. Connect the SPST switch
between X2-1 (Knocker enable) and X2-2 (shared CAPS input from I-PAC).
In order for this circuit to work, you must enable LED support in MAME32.
I have included a snapshot of the correct setting for MAME32. Brad Oldham
states, "Ensure the RDTSC timing system in enabled." I have perfect results
with RDTSC disabled. Actually, I have sluggish, weird joystick performance
with RDTSC enabled on my machine. You may have to experiment with this
yourself.
| L1 |
A-5195 Gottlieb/Premier Coil P/N# A-5195 (Marco Specialties) |
| Q2 |
2N6045 Transistor (TIP 102 will work) P/N# 2N6045 (Marco Specialties) |
| D1 |
Diode usually included on the A-5195 coil (Marco Specialties) If not - Add 1N4004 |
| SW1 |
SPST Switch (Radio Shack) |
| C33 |
0.1 uF 200 volt radial capacitor P/N# C_1M200VR (Marco Specialties) |
| R1 |
1K Ohm ¼ Watt Resistor P/N# 271-1321 (Radio Shack) |
| R4,R5 |
10K Ohm ¼ Watt Resistor P/N# 271-1335 (Radio Shack) |
| F6 |
1 Amp Slo-blow Fuse P/N# 270-1021 (Radio Shack) |
| PS1 |
P/N # 273-1668 (Radio Shack) 30VDC AC-to-DC Adapter |
Knocker
Assembly |
Knocker assembly off an old pinball machine (Rebuild using the A-5195 coil) |
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