Editing IBM 5120 Troubleshooting Guide (section)

== Common Field Symptoms and Resolutions ==

* '''Won't power on''' — mains lead, switch, fuse, PSU primary.
* '''Power LED but no display''' — PSU bulk filter caps; see [[IBM 5120 Capacitor Replacement Guide]].
* '''Banner appears but system hangs on keystroke''' — keyboard cable or PALM input handling.
* '''Garbled banner''' — Language ROS or socket oxidation.
* '''Drive A: reads but Drive B: doesn't''' — drive select jumper or cable terminator.
* '''Both drives spin but won't read''' — head clean, then alignment, then belt.
* '''Random reboots / hangs''' — bulk filter cap ESR rising; recap PSU.
* '''Smell of fish from PSU''' — RIFA X2 mains-suppression capacitor venting; replace immediately.
* '''CRT loses focus after warm-up''' — flyback transformer insulation breakdown; replacement requires donor.