The game sometimes will not boot. The 5 V at the power supply falls to almost nothing when the output plug J1 is connected, while 12 V stays good. Pressing on the power supply board makes the game turn on or off.
Game boots only sometimes, 5 V drops out: cracked diode D6 on the power supply
Cause: A cracked 1N4004 diode (D6) in the 5 V section of the power supply. It looked fine and was still factory soldered, but was broken inside.
Checks
- Measure 5 V at TP1 against ground at TP2 on the power supply, with and without J1 plugged in; check 12 V at TP3.
- Try a known good power supply to confirm the fault is on that board.
- Press gently on the board while watching the 5 V to find an intermittent part or joint.
Fix
- Replace diode D6 on the power supply board.
Line-derived AC is present on the power supply input while powered; switch off and unplug before handling the board.
Systems
Games
Related tips
- Rebuilding the +100 V section of the power supply
- Rebuilding the -100 V section of the power supply
- Testing coil diodes on the auxiliary power driver board
- A cracked coil diode keeps killing its driver transistor
- Testing a coil diode
- Testing the diode on a coil
- Which way a coil diode goes
- Which way a coil diode goes
Source: Pinball Repair help group!! (Facebook group)