Do not leave out the 1k pull-up when fitting a DS1811
The DS1811 alone cannot supply enough current to pull the reset line high for every chip that uses it. Without the 1k pull-up from +5 V to its reset pin, the MPU may start only some of the time.
Systems
Related tips
- DS1811 reset chip: which version to use
- Good MPU stays LED-on with a PC power supply
- MPU on the bench always stops one flash short
- Bally/Stern MPU LED self-test: what to expect
- Reading the MPU flash code
- MPU LED locked on with no flicker: likely causes
- Testing the MPU reset circuit at U9 pin 40
- MPU U9 voltages that show a working reset section
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Two, Clay Harrell (pinrepair.com)