The game coins up and plays, but each score display shows only one zero in the last digit and the credit count is blank; scores never change.

Scores show only a single 0 and the credit display is blank: failed 7404 at IC31

Cause: A 7404 hex inverter (IC31, next to LEDs 3 and 4 on the board) had failed.

Checks

• Check the logic chips that drive the display data and strobe lines with a logic probe; a dead output on an inverter can freeze every display at one digit.

Fix

• Remove the failed 7404 at IC31, fit a socket and install a new chip.

The displays run on high voltage; power off before working on the boards.

Games

• Roy Clark Super Picker

Related tips

• Missing digit on one or more score displays
• Displays never show the digit 1
• Missing segment on one or more score displays
• Display chips on the CPU board fail after swapping displays
• Blanking circuit parts: C32/C84, IC7, Q5/Q1 and IC23
• Damage after the black and white plugs were swapped
• Boot stops after the ninth LED flash: IRQ fault

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