Game Plan THUNK! - When some GP machines are started they sometimes fire one or more solenoids such as the ball kicker, drop target, etc. This can be annoying as well as potentially hazardous to the driver transistor so we have fixed this by adding a Reset Supervisor IC MCP-101 to pin 19 of the 74154 1-of-16 decoder IC. Cut pin 19 very close to the solder pad and bend it up, then solder the MCP-101 to the filter capacitor and Pin 19 as shown here...
You can order a replacement MPU (around $195US) for either cocktail or regular Game Plan games from:
Echo Lake Pinball Service & Sales
(Note, Jim is still in business! This is correct as of June 25th, 2020!)
Tips for specific games (from rec.games.pinball newsgroup):
Problems with the SWITCH CATCHER (PCB under playfield near left flipper):
>>> When I disconnect the Switch Catcher from the game (Supernova)
>>> everything works. When I attach it the game will not start. I have
>>> replaced the three major IC's and checked all caps, diodes, and
>>> Anyone have any thoughts?
>> Yes this can easily be fixed, If everything works fine when the switch
>> catcher is disconnected then this will fix it...
> The "switch catcher" Seems to control All of the switches that stem
> from the spinwheel at the top of the PF. It is located at the bottom
> left under the PF and has a 15 pin connector. There are the 4
> switches, 4 strobes, and 4 lines. It also gets 2 ground feeds and 1
> +5v power feed. With the switch catcher disconnected, the above 4
> switches do NOT work so leaving it off is really a bum option.
Switch Catcher - #02-70051B.
It looks like this circuit board is indeed designed to "catch" switches with short duration impulses using flip-flop logic that is tripped when a switch is closed and is reset when the next strobe pulse comes along.
I checked the PCB on my working Super Nova and found the following pins (counting from the front of the cabinet to the back) are all High (roughly 5.0VDC) #1, 2, 3, 4 (could be pulsing), 5, 6 (Vcc) 8 (High pulsing low), and 9 (could be pulsing).
Switch inputs are #1, 2, 3, and 5 - all should be High as the switches should be open.
The common./ground pin is (of course) Low - #13 & #12 (no wire to 12).
Pulsing pins are the Strobe Inputs - #7 (ST-0), #10 (ST-1), #14 (ST-2) and #15 (ST-3).
If any of your reading are different, then first check the PCB for cracked/cold solder connections to the long Molex pin row, then check switches for jammed closed, finally do the Diode Test on the TTL and LM339 gates...
http://www.flippers.com/service.html#tips (diode test)