from post #531
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The datasheet for that series of PROMs says that the power pins are 24 and 12
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You MUST connect pins 24 and 12, these are the power pins of the PROM. Arduino +5V to pin 24, Arduino GND / 0V to pin 12. The PROM needs to be correctly powered before it can do anything sensible.
The required states of the chip select pins to enable the chip is deduced partly by looking at how they are connected in the circuit diagram, and partly by looking at the datasheet for the PROMs.
In the case of the character PROM which appears to be a 2K device, don't connect the Arduino's A11 address output to anything, that pin is only connected when reading 4K PROMs.