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Pinball Rehab

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Pinitech WPC Reverse Switch Tester Review Pinitech WPC Reverse Switch Tester Review Hot

Pinitech just announced a WPC Reverse Switch Tester (see Image 1), which I was able to beta test.  I can say definitively that it should be part of the toolkit for anyone who works on pinball games.   This simple, inexpensive product (un-assembled $10 and assembled $15) will turn the several hour process of identifying phantom switch closures into a simple 30 minute project.

If you opt for the kit it can be assembled in a few minutes as only four connectors need to be soldered onto the board.

There are several switch/diode problems that can cause phantom switch closures (when a switch is closed, one or more other switches also indicate as being closed).  The Reverse Switch Tester will quickly identify all of the following issues.

  • Reversed diode.
  • Shorted diode.
  • Switch/diode lead shorted to ground.
  • Diode lead touching switch lead.

How it Works

The switch matrix has 5 columns (send) and 8 rows (receive).  Cross-talk between the rows and columns is prevented by a diode installed on each switch, thus the signal can only travel in one direction (from send to receive).  The Reverse Switch Tester swaps the columns and rows so the row is now the send line and the column is the receive line.  Now the blocking diodes are reversed and none of the switches should work.

The magic is due to the fact that if any of the switches do work with the board installed then you have one of the problems listed above.

Image Gallery

Pinitech WPC Reverse Switch Tester Review
Pinitech WPC Reverse Switch Tester Review
Pinitech WPC Reverse Switch Tester Review
Pinitech WPC Reverse Switch Tester Review

In Image 2 the blue line shows the standard setup without the rows and columns swapped.  The signal travels from the column through the closed switch and to the row.  The green line shows the flow after the rows and columns are switched.  Even though the switch is closed the diode blocks the signal and no switch closure is sensed.  The yellow line shows where the diode is reversed and the signal passes and if the switch is closed it will be detected.  The purple line shows the same scenario except with the diode shorted or a diode lead shorted to a switch lead (thus bypassing the diode).

Note: The arrows indicate the direction of the send signal, which is reversed after installing the test board.

Testing

The installation process is simple, although it may vary slightly on some games (see Images 3 and 4).

  1. Turn the game off.
  2. Remove the row/column connectors from any opto boards.*
  3. Remove the row and column connectors (J207 and J209)
  4. Install the board across the J207 and J209 headers.
  5. Reinstall the row and column connectors on the Reverse Switch Tester board.
  6. Turn on the game and go into switch edge test.

* This should be done anyways to ensure as part of the standard troubleshooting process to eliminate them as a cause of the phantom switch closures.

If you get a "Check Fuse XXX" error then you will have to remove the row and column connectors and install the test board while the game is on.  The easiest way to do this is to slightly remove the row and column connectors (pull them up about 1/3 of the way) prior to turning the game on.

After going into switch test if you get a switch row ground error (remember these are now actually the column, or send, lines) then there is a short to ground on one of the columns.  At this point you would visually inspect the column wire and each switch for a short to ground.  If you don't get any errors when entering switch test then continue with the testing as follows.

Go through all of the switches while in switch edge test, closing one at a time.   None of the switches should indicate a closure.  If one does then that is your problematic switch.  Inspect it for a reversed diode, test for a shorted diode and inspect for a diode lead shorted to a switch lead (this can also be an internal issue with the switch).

It really is just that easy.