Editing Acorn FileStore Troubleshooting Guide (section)

== Power supply checks ==

Make the measurements with every connector in place. To measure current, break into the red (+5&nbsp;V) or orange (+12&nbsp;V) lead with the power off, then switch on; currents change in the first seconds after power-up.<ref name="sm" />

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''Supply limits and currents (service manual fault finding sections)'''
! Unit !! Rail (lead colour) !! Limits !! Expected current
|-
| E01S board || +5 V (red to black) || 5.0 to 5.25 V || 0.9 to 1.2 A, 1.5 A maximum; falls by about 100 mA after the EPROM has been copied to RAM
|-
| E01S drive connector || +5 V || 5.0 to 5.25 V || Per drive: 50 mA standby, 275 mA reading or writing
|-
| E01S drive connector || +12 V || 11.4 to 12.6 V || Per drive: 500 mA motor start, 140 mA seek, 90 mA reading or writing
|-
| E20 || +5 V (red) || 4.9 to 5.2 V || Hard disc about 1 to 1.5 A; host adaptor about 500 mA
|-
| E20 || +12 V (orange) || 11.4 to 12.6 V || Hard disc up to 4.5 A, falling to about 2 A at speed
|-
| E40S, E60S || +5 V (red) || 4.9 to 5.2 V || 0.7 to 1 A
|-
| E40S, E60S || +12 V (orange) || 11.4 to 12.6 V || Up to 2.5 A, falling to 0.4 to 0.9 A within about two seconds
|}

For the E01S board current, fit the Econet module, disconnect the SCSI bus from other units but leave the terminator on, and close the flap. The floppy drive power plug carries, in order, +5&nbsp;V, 0&nbsp;V, 0&nbsp;V and +12&nbsp;V. Acorn measured drive currents with a small break-out board in the lead; avoid shorting it against the drive tops or the supply board.<ref name="sm" />

The supplies are exchange assemblies in Acorn's lists, with no circuit published.<ref name="sm" /> A supply that fails these limits needs component-level work on the supply itself or a replacement; see [[Capacitor Failure Symptoms]].