Why diodes on 555 lamp boards crack

A diode soldered in hard against a lamp board can crack: the body lengthens slightly with soldering heat and pulls as it cools, and vibration finishes it. An open diode leaves its lamp dark.

Systems

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

Related tips

• Diode orientation on #44/47 lamp sockets, and 555 sockets
• Testing lamp-row drivers with a test lamp
• Testing lamp-column drivers with a test lamp
• Test a lamp socket diode in place
• Lamp diodes sit on small boards at each socket
• Test a 1N400x diode on a coil, lamp socket or switch
• Testing a coil diode
• Testing the diode on a coil

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