Referring to my CFTBL manual on game power up LED D19 and D21 turn on for a moment then D19 turns off and D20 starts to blink rapidly. D21 remains on. So, if LED D20 blinks one time - rom error @ u6. Blinks two times-ram error @ u8. Blinks three times-custom chip failure @ u9. That should narrow it down!!!!
