Editing IBM 5110 Maintenance Guide (section)

== PSU Voltage Checks ==

Probe each rail at the planar power connector. Tolerances (typical linear PSU):

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''IBM 5110 PSU rail tolerances'''
! Rail !! Approximate target
|-
| +5 V (logic) || +4.75 V to +5.25 V
|-
| +12 V || +11.4 V to +12.6 V
|-
| &minus;5 V / &minus;12 V || As marked in MIM SY31-0550
|-
| CRT high-voltage anode || ~9–11 kV (5-inch CRT)
|}

Out-of-tolerance rails after recapping bulk caps suggest a series-pass regulator transistor failure.

The 5114 has its own PSU with rails appropriate for the 8-inch floppy drives:

* '''+5 V''' for drive logic.
* '''+12 V''' or '''+24 V''' for spindle motor and head load solenoid (depends on drive vendor).
* '''&minus;5 V''' bias rail.

Verify per the 5114 MIM SY31-0551.