Using the test EPROM memory test

Steps

• Fit all MPU chips with the test EPROM in U6 and the test LED on U9 pin 15 (or J5 pin 16). Do not use the 9316/2716 adaptor for this test.
• Power up; the LED flashes steadily (the PIA test).
• Press the red button on the MPU. The LED goes out, then gives one flash after about a second if U7 (6810) is good.
• Bally -17/-35: a second flash about 5 seconds later, followed by steady flashing, means U8 (5101) is good.
• Stern MPU-200: steady flashing just one second after the first flash means U8 and the extra 5101 at U13 are both good; a 5-second gap means U13 is missing or bad.
• No flash, or only one, means U7 or U8 is faulty.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35
• Stern MPU-100
• Stern MPU-200

Related tips

• Setting up an MPU for the test EPROM
• Making the test LED for the test EPROM
• U9 signals with the test EPROM running
• U6 select signals with the test EPROM
• Checking the PIA outputs with the test EPROM
• Never use a TMS2716 EPROM
• Which EPROM format to burn
• Mod1: two 2716 EPROMs at U2 and U6 on a -17 or M-100

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Two, Clay Harrell (pinrepair.com)