Testing a 74LS374 driver latch with the diode setting

Steps

• Set the meter to diode test with the game off.
• Put the red lead on ground and touch the black lead to each pin of the chip in turn.
• Every pin except power and ground should read about 0.4-0.6. A pin far outside that points to a failed chip.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• Testing a coil diode on the driver board
• Taking the power driver board out of the backbox
• Learn the power driver board layout first
• 20-second test for shorted coil driver transistors
• Replace the pre-driver along with a failed driver transistor
• Where the WPC coil and lamp drivers sit
• WPC power driver board versions and where they fit
• How a WPC coil, flasher or lamp driver chain works

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Two, Clay Harrell (pinrepair.com)