Logic 5 V reads over 5.25 V on Bally/Stern: the R49 boost resistor
On Bally and Stern solid-state games a 100 ohm resistor (R49) between the 5 V regulator's output and ground raises the regulator's output by about a quarter volt. Regulators vary from about 4.75 to 5.25 V, so one on the high side can end up near 5.5 V, which shortens chip life. If the logic supply measures above about 5.25 V, cutting out R49 brings it down; the games run fine on a clean 4.75 V. A failed R49 can also be the reason for no 5 V at the test point.
Systems
Related tips
- Solenoid driver TP1 below 5 V with TP5 normal
- Solenoid driver TP5 under 13 V
- Replace filter cap C23 on every game
- Testing C23 for AC ripple
- Replacing filter cap C23
- Only about 1.6 V at solenoid driver TP1
- Route of the +12 V supply to the MPU and 5 V regulator
- MPU locks with LED on because of C23 or Q20 on the solenoid driver board
Source: Pinball Repair help group!! (Facebook group)