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Pinball Rehab

pinball repair and restoration

Building a WPC Test Fixture Building a WPC Test Fixture Hot

As my Dad would say, there are several ways to skin a cat.  So while this may not be the ultimate WPC test fixture, the design was limited by a couple of my personal objectives.  First I didn't want to mess with a transformer, and secondly I did not want high voltage on the bench. 

While this design precludes the possibility of troubleshooting DMD's or the high voltage section of dot matrix controllers, I can live with that.  Most DMD problems can't be fixed anyways, and the high voltage section of the dot matrix controller can be easily tested while the board is in the game.

I will be building the WPC test fixture in phases, with the first phase including the CPU, dot matrix controller and LED display (see Image 1).

Parts Requirement (Phase 1)

  1. Vishay LEE-128G032B LED (discussed below)
  2. WPC CPU board.
  3. WPC Dot matrix controller.
  4. Power supply (5 volts at 5 amps and 12 volts at 2 amps)
  5. Game ROM (WPC Test ROM recommended)
  6. 18 gauge wire.
  7. 2 each 7 pin female .156 IDC or crimp-on connector.
  8. 8 pin female .156 IDC or crimp-on connector.
  9. 4 pin female .156 IDC or crimp-on connector.
  10. Several standard pinball ribbon cables: 2x13 (26 pin), 2x17 (34 pin) with 4 connectors and 2x7 (14 pin).
  11. SIegecraft Switch Matrix Tester or a jumper with 1N4004 diode installed inline.
  12. 2 each inline fuse holders and fuses (5 amp and 3/4 amp).
  13. Power cord inline switch (if your power supply does not have a switch).
  14. A couple of .100 female to female jumpers and 1N4004 diodes.
  15. Optional: 12 pin female .100 IDC or crimp-on connector, 4 N/O momentary switches and 4 1N4004 diodes.

IDC or crimp-on connectors can be found at Big Daddy Enterprises or Great Plains Electronics, which also carries the ribbon cables.  You can pick up the momentary switches, inline fuse holders, power cord switch and the .100 female to female jumper at your local electronics store.

LED Display

In order to eliminate the need for high voltage I went with an LED display.  I used the Vishay LEE-128G032B red LED display, which runs on 5 volts and is available from Mouser for $267.  There are other LED products available, but they cost more.  If you do go with another option make sure it runs off 5 volts.

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Building a WPC Test Fixture
Building a WPC Test Fixture

Power Supply

The first thing you will need is a power supply with 5 volts at 5 amps and 12 volts at 1 amp.  This is sufficient for our first phase, but additional voltages and/or higher current may be needed as we add more boards to the test fixture.

I'm using the Suzo-Happ Power Pro 110 Watt power supply, which provides 5 volts at 15 amps and 12 volts at 2 amps.  This selection may be modified as I continue.  You could use an old computer power supply instead.

Power Wiring

Next we'll create a power cable using two 7 pin .156 IDC connectors and some 18 gauge wire. You can also make the power cable using crimp-on connectors if you prefer.  If you want to plan ahead for the next phase, you can add two more connectors wired in the same fashion.

Wire the two connectors using the following pin connections.  You only need to run one wire for ground, 5 volts and 12 volts, but connect each wire to two pins as shown below.  My first section of wire (from the power supply to the first connector) is 3' long and the second section (from the first to second connector) is 2'.  Adjust this as necessary for your layout.

  • Pins 1 and 3 - ground
  • Pin 2 - key
  • Pins 4 and 5 - 5 volts
  • Pins 6 and 7 - 12 volts

Additionally it's a good idea to fuse the 5 and 12 volts sources.  Use an inline fuse holder with a 5 amp fuse for the 5 volt line and a 3/4 amp fuse for the 12 volt line.  If your power supply does not have an on/off switch (as is the case with the HAPP supply) add an inline switch to the power cord.

Next we'll need a power cable from the dot matrix controller to the Vishay LED.  You'll need an 8 pin .156 for the dot matrix controller and a 4 pin .156 connector for the Vishay LED.  Wire them as follows using about 2' of wire.

Dot Matrix Controller (8 pin)

                      Dot Matrix ControllerVishay LED
Key Pin 3 N/A
Ground Pin 5 Pins 3 and 4
5 Volts Pin 6 Pins 1 and 2

Test Fixture Connections

  1. Connect the first connector on your home made power cable to J210 on the CPU and the second connector to J606 on the dot matrix controller.
  2. Take the 8 pin to 4 pin cable and put the end with 8 pins on J604 on the dot matrix controller and the end with 4 pins on J2 on the Vishay LED.
  3. Connect the 26 pin ribbon cable from J201 on the CPU to J602 on the dot matrix controller.
  4. Connect the 34 pin ribbon cable from J202 on the CPU to J601 on the dot matrix controller.
  5. Connect the 14 pin ribbon cable from J603 on the dot matrix controller to the VIshay LED.

Note: Pay attention to orientation on all ribbon cables (pin 1 should have the red stripe).

Check all the power wiring using a DMM in diode/continuity mode or in voltage mode before the boards are connected.

Direct Switches and Switch Matrix

There are a couple of ways to control the diagnostic switches.  I use a .100 female to female jumper with a 1N4004 diode installed inline.  Pin 10 on J205 is ground and pins 9 through 6 are the diagnostic switches.  Pin 9 is enter, pin 8 is plus, pin 7 is minus and pin 6 is escape.

Place the end of the jumper with the banded side of the diode on pin 10 (yes I know the manual says pin 12 is ground, but it's actually pin 10) and then momentarily touch the other end of the jumper to pins 9, 8, 7 and 6 to navigate the diagnostic menu.

If you want to get fancier you can purchase a set of diagnostic switches or four N/O momentary switches and add a connector.  

Using a 12 pin .100 IDC, or crimp-on, female connector pin 10 goes to one side of each of the four switches.   Install a 1N4004 diode on the other side of the switch with the banded side of the diode towards the switch.  Run a wire from pin 9, 8, 7 and 6 to each of the diodes (one wire per diode). See Image 2.

If you want to match the layout of the diagnostic switches put the wire from pin 9 on the left switch, then the wire from pin 8 on the next switch, etc.

For the switch matrix you can either use the Switch Matrix Tester from Siegecraft or use a jumper cable.  For the latter, install a 1N4004 diode inline and test with the banded side of the diode on the column pin.

Check Fuses F114 and F115 Error Message

If you are not using the Siegecraft product you can get erroneous error messages telling you to check fuses F114 and F115.  This happens because the CPU expects to see a closed switch at position 24.  If it does not, it presumes the 12 volts is missing and displays this error.

In reality, switch 24 does not exist.  Instead there is a diode, mounted on the coin door interface board across column 2 and row 4.  If the CPU does not see this closed switch the error is displayed.

This does not happen with the Switch Matrix Tester since there is a jumper on the test board that simulates switch 24.  You can also prevent this issue by connecting a jumper from column 2 to row 4.