The selftests on modern pinball machines are very nice, but they assume that the cpu works perfectly, or you won't be able to start it. As I always want to keep the test program as simple as possible, it should just indicate which major parts have a problem. Later things have changed and it became better to use simpler ICs like RISC processors (Reduced Instruction set) which means less instructions but faster processors. This unfortunately made CPUs very complicated. Back then it was "very good" to have CPUs with many and versatile instruction sets. This IC is one of the very first generation of CPUs. Read-out is going directly towards the output pins, so we test this memory in the output section of the test. So the test program can write but not read IC21. One last remark, the memory chip IC21 is not included in the memory test, this is impossible, as the data is being written through the databus, but reading does not happen through here. It was necessary to test the inputs, as this board does not use PIA's for in- and output. We shall connect the input pins at connectors CN9 ( there are 8) one by one to ground, and every time the cpu stops blinking and goes " out", at the moment we release the input pin the LED restarts blinking. Meanwhile a "control LED" is blinking rapidly. If both memory chips are ok, the test will automatically continue the "input test". If something is wrong then the test will continue to run the memory test. At startup all outputs will go up and down in rhythm, between 5 and 0 volt. You should visit his site, as a lot of technical information about Zaccaria is collected there, and it was the only website on which I found some technical information. David tried out this repair method and reported positive results and made several corrections for the English translation. First generation, Earth Wind and Fire, Hot Wheels, Future World, House of Diamonds, Winter Sports, Shooting the Rapids, Fire Mountain, Space Shuttle, Star God, Locomotion.
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