Service manual

Appendix D - DC insulation testing - class 1
UK information only
Equipment required
A portable appliance tester or an insulation tester
that provides 500V DC ONLY.
Note that the computer contains RFI capacitors on
the PSU input.
It is recommended that the calibration and operation
of the instrument is checked frequently enough to ensure
its accuracy.
DANGER:
THE FOLLOWING TEST INVOLVES HIGH VOLTAGES. ALL
NECESSARY PRECAUTIONS MUST BE TAKEN TO
ENSURE OPERATOR SAFETY DURING TESTING. NOTE
THAT THE OPERATOR MUST BE TRAINED AND
COMPETENT.
DANGER:
SWITCH OFF THE COMPUTER, DISCONNECT IT FROM
THE MAINS SUPPLY, AND DISCONNECT ANY EXTERNAL
PERIPHERALS AND CABLES BEFORE CARRYING OUT
THIS TEST.
Before testing
Check the mains lead and plug for any physical damage
and replace if necessary.
Test procedure
Consult the instructions supplied with the test equipment.
The test should be performed on a fully assembled
computer.
The equipment must be tested with the mains lead it will
be operated with.
1 Insert the mains lead either into the portable appliance
tester, or into an adaptor, as shown below.
2 Move the computer's power switch to the ON position.
3 Apply the test voltage for LESS than 10 (TEN)
seconds and then measure the resistance.
4 Pass level: GREATER than 2 (TWO) Ma
5 Move the computer's power switch to the OFF position
and remove the mains lead from the portable appliance
tester.
Testing with an insulation tester
Insulated terminals and leads
Appendix D - DC insulation testing - class 1 Issue 1, November 1991 D-1