Editing Osborne Executive Troubleshooting Guide (section)

== Preliminary & Power-up Checks ==

Begin by confirming the Executive’s power supply and startup sequence, as many faults stem from PSU or connector issues.

# Unplug the unit and visually inspect for burnt components, leaking capacitors, or corrosion—especially near the power input and CRT area.
# Test the mains fuse and the internal 5A fuse on the PSU board.
# With a multimeter, check voltages at the mainboard edge connector:
#* '''+5V DC''' (logic supply)
#* '''+12V DC''' (floppy and CRT)
#* '''-5V DC''' (RAM bias)
# If voltages are missing or out of range, recap the PSU and check for failed rectifiers or voltage regulators (notably the 7812, 7805, and 7905).
# Remove all floppy drives and expansion cards; attempt to power up with mainboard only.
# Inspect the reset circuit (NE555 timer and associated components) for failed capacitors or stuck reset.

{| class="wikitable styled-table"
! Symptom !! Likely Cause !! Action
|-
| No power, no fan || Blown fuse, failed switch, dead PSU || Replace fuse, test switch, recap/repair PSU
|-
| Fan runs, no CRT glow || CRT supply failure, loose CRT connector || Check 12V rail, reseat CRT connectors, test flyback transformer
|-
| Powers up, but no beeps or display || Mainboard not receiving correct voltages || Confirm all rails at edge connector, check for shorts
|}