DIY Switch tester tool for WPC pinball machines

This tool showed up on ebay Germany a while ago..
The text with it said this was a switch matrix test tool, developed by someone in Germany who worked for a daughter company of Nova (large distributor of Williams in Germany).
Eventually it sold for 57 euro.

57 euro for a small pcb ? That's a lot of money.. especially as this part does not looks very complicated and looks to be a pcb with some connections but no active components.

When I sent the picture to Leon he was fast to analyse what it is and write how to make it yourself.
The idea behind it is very clever. What it does is switch the rows to columns (and columns to rows) so the polarity of the diodes is switched. That way when you are into the switch matrix test, a switch that works correct will not report at all. Only switches with bad (open) diodes will be active in the test.

Problems with the switch matrix can be in 2 locations: on the playfield wiring or on the cpu board itself.
If the problem is on the cpu board itself, you can test it.
But if your cpu board tests fine, and there still is a problem, the error is somewhere in the wiring on the playfield. And then this tool will help you find it.

This is not a tool you will use often.. this kind of switch matrix problem, where a whole row or column lights up when you press one switch, fortunately doesn't happen often.
But the few times you have a weird problem on a game with the switch matrix that you just can not solve, this tool can save a lot of time. If you don't have it you may spend hours tracing wires, unsoldering them, testing diodes, .. Most people hate troubleshooting the switch matrix, not because it is a difficult job but because it is so time consuming and some switches are very hard to reach (especially the diodes on the switches).

It is not difficult to make this yourself. All it does is plug in between the cpu board and the connectors.
The reason you cannot switch connectors J206 and J208 on the cpu board is simple: they are not keyed alike.
So all this pcb does is connect the connector of J206 to the pins of J208 and vice versa.
For a few $ worth of parts and half an hour of soldering you can make this tool yourself.