Checking PIA outputs with Leon's test EPROM

Steps

• Confirm +5 V at the GND and +5 V test points by the battery, and note which of the three LEDs are lit.
• Remove the CPU board, labelling each connector as you unplug it.
• Lay it on an insulated mat and power it from a +5 V supply at the test points or CN17.
• With power off, fit the test EPROM at 5C, then power on. The PIA LED (driven by PIA 11B) should flash, and blanking should give very short flashes.
• With a logic probe (or a manual-range meter), check PIA pins 2 to 17 on each PIA; each should swing between 0 and 5 V.
• If no PIA toggles at all, the fault is further back: the CPU, EPROM socket, RAM, or the address, select or data circuits.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• Test program does not run at all
• One PIA output does not toggle under the test EPROM
• Program runs but the PIAs never respond
• PIAs or the EPROM are never selected
• CPU EPROM jumpers J4 and J5
• CPU board PIA positions and jobs
• CPU jumpers J4 and J5 set the EPROM size at 5C
• Running the Data East test EPROM

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)