XX and YY in the message are code characters defined as follows:
XX= 01 = ZERO PAGE RAM FAILURE, check 6532
n3 = ROM FAILURE. Any number in the XX position ending with a 3 (for example, 23, 33, etc.) indicates a ROM failure. The first digit (2 and 3 in the previous example) points you to the appropriate chip that needs to be checked. The code for the any number ending with 3 in the XX position is as follows:
XX= Chip to Check
Note: The message reflects the first bad chip it encounters, in numeric order. It is possible for chips following it to also be bad.
04 = INTERRUPT FAILURE, check 6532.
?? = FAULTY COMMUNICATIONS. Check 6520 at 9B.
Here is the code for the second two numbers in the YY position.
YY= 40 = Communication from Logic Board to Audio failed. Check 6520, both locations 88 and 9B.
80 = Communication to Logic Board from Audio failed. Check 6520, at locations 9B and especially 8B.
<0 = Communication between Logic and Audio failed. Check 6520, both locations 8B and 98.
Also, the symbol <0 in both the XX and YY position, along with a hum or random notes and no beep after power on, may indicate a failure in 3A and/or 7A.
The following drawing points out the three Individual audio adjustments and the location of the DIP switch. The audio board rides piggyback on the logic board, mounted on the right wall of the game, when viewed from the rear service door.
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