| Game Plan Pinball tech tips page... |
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We have just finished our replacement Z80 RAM/ROM board and it fixes about 80 - 90% of Game Plan MPU problems that are related to either battery corrosion or failing RAM or ROM. A simple plug-in sub-board this is an elegant method to get your board running again.
Only $125US plus shipping. Currently out of production I'm afraid, |
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On another note, I have designed a replacement for the RESET circuit that often fails in these games-much simpler as you replace a bunch of resistors and transistors with a single IC (called a CPU Supervisor), and cut and jumper a few traces. I shall expand that here in the future. |
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To replace the ROM memory with a single EPROM (2764) all you need to do is first program the 2764 with the game code loading from 0000h up. Next bend out pins #20, 22, and 23 on the 2764. Then solder a jumper wire on pins #26, 27, 28 and 1 (tie all to 5VDC). Now refer to the photo to the left and add jumper wires from 2764-P2 to A12, 2764-P23 to A11, 2764-P22 to A15, and 2764-P20 to /MREQ. Works for me! |
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Battery corrosion is a real problem for Game Plan MPUs, please read up the details on my battery page...
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Weird Solenoid or Lamp problems? Do you not get any sounds or are they mixed up, yet the MPU and Sound boards both seem to be ok? Then take a look at this capacitor - it might be broken or leaky. This capacitor is a critical timing capacitor. |
Replacing the original Harris HM6551-9 CMOS RAMs with a pair of 5101s |
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MPU-2 (and MPU-1) 1st cut solder pads between Pins 18 & 19 on both U6 and U7 |
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MPU-2 (and MPU-1) should look like this now. |
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MPU-2 (and MPU-1) cut trace from U5-Pin 8 |
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MPU-1 mods to topside of MPU - add 74(LS/HCT)04 (Piggy Back) on top of U5 (print out image). You need this inverter as there are no free gates left on the MPU-1 PCB, and we will need two inverter gates. For the MPU-1 PCB you have to connect Pin 9 of the Piggy Back to U5-Pin 8, bend out Piggy Back-Pin 8 and add a jumper to the cut trace.
This is almost identical to the MPU-2 mods except that MPU-2 has a spare inverter gate on U24 that we will use to invert U6/7-Pin17, thus we will only need one gate on the Piggy Back. |
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MPU-1 alternate picture showing cut trace at U5-Pin8 and jumper to Piggy Back-Pin 8 and jumpers to U6-pins 20 and 18 as described below. |
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MPU-1 mods to underside of MPU board (same solder pad cuts as MPU-2 below) |
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MPU-2 Now...(print out this image)...add jumpers between U6-Pin 20 and Piggy Back-Pin 11 (input), then jumper between U6-Pin 18 and Piggy Back-Pin 10 (output). This sets up the OE pin so it is the opposite of R/W. Add jumper between U6-Pin 19 and U7-Pin 19 (note that U6 & U7 Pin 18's are already connected with a trace on the top side of the PCB). Next jumper U5-Pin 8 to U24-Pin 11, then jumper U24-Pin 10 to U6-Pin 17. |
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MPU-2 Location of Piggy Back and the required connections. |
You can order a replacement MPU ($195US I beleive) for either cocktail or regular Game Plan games from:
Jim Francesangeli
Echo Lake Pinball Service & Sales
925 Marwin Dr.
Hinckley, Ohio 44233
tel: 330-278-2228
jvbuzzard(at)earthlink(dot)net |
Flippers.com 
