A new replacement CPU board reports a U38 PIA failure at power-up. Swapping the PIA with another one on the board does not move the error, and the game otherwise plays normally.

Replacement CPU board keeps reporting a U38 PIA fault: try another 6802

Cause: The 6802 processor was flaky; it had seemed fine in the previous board.

Checks

• Check the +5 V supply at the CPU board first.
• Swap the PIA at U38 with another PIA; if the error stays at U38, the PIA itself is not the cause.

Fix

• Replace the 6802 processor with a known-good one.

Systems

• Williams System 11A

Games

• F-14 Tomcat

Related tips

• A 6802 CPU chip works in place of the 6808
• CPU chip types: 6800 on System 3/4, 6802 or 6808 on System 6/7
• CPU still will not boot after the basics
• Transistors, diodes and chips to keep for CPU and driver repairs
• System 6/7 sound board can take a 6802 in place of the 6808 and 6810
• Test program does not run at all
• All sounds suddenly wrong and background gone: bad 6802 on the sound board
• Occasional U10 PIA error at power-on, but the game plays

Source: Pinball Repair help group!! (Facebook group)