I am trying to help Shlockdoc with his FT, How would we test the blanking circuit? I'm thinking that is the issue since D19 never turns off when the game doesn't boot. It's that or its a capacitor in the power supply that is failing. If you power on and doesn't boot, you can flip it off and immediately back on and it will boot. If you wait a minute it will almost always not boot after sitting off for a minute. I did have one time where it had been off and powered it on and it booted first try.
No visible damage to the cpu board on the front, I have not removed it from the game yet, but very clean on the front side. I did notice that this is a re-import and the resistor bank is still configured for Europe if that has any bearing on anything other than language.
Voltages at pin 5 of J210 were the same in booted mode and non booted mode of the CPU board.
I found this article on another site. How would one go about actually performing these tests?
If D19 doesn't turn off the CPU will not boot. First check pin 3 of U21 (blanking signal from the ASIC), which should be high. If it is high and D19 doesn't turn off then there is likely a problem with the amplifier chips, either U21 or U5. If it is low then the signal from the ASIC chip is bad indicating a problem with the ASIC, the 6809 processor or one of the clock circuits.
You can test the 8MHz and 32Khz clock signals (see Imageat pins 34 and 35 on the CPU. These signals come from pins 81 and 82 on the ASIC. If one or the other is missing check the clock inputs to the ASIC at pins 55 and 70. If either input is missing check crystal X1 (32Khz) or crystal X2 (8Mhz), as appropriate, and their associated circuitry.