Safety Precautions; Leakage Current Check - Mitsubishi Electric XD221U Service Manual

SAFETY PRECAUTIONS

North america
NOTICE: Observe all cautions and safety related notes located inside the cabinet and on the chassis.
Warning
. Operation of this projector outside the cabinet or with the cover removed presents a shock hazard from the projector power
supplies.
. When a short-circuit has occurred, replace those components that indicate evidence of overheating.
3. Grounding circuit continuity is vital for safe operation of equipment. Do not remove ground connection while the power cord
is still connected to the supply. Disconnect supply before servicing.

Leakage current check

Before returning the projector to the customer, it is recommended that leakage current be measured according to the follow-
ing methods.
1. Cold check
With the AC plug removed from the AC 00 to 40 V, place a jumper across the two AC plug prongs. Turn the projector AC
switch on. Using an ohm-meter, connect one lead to the AC plug and touch the other lead to each exposed metal part (metal
cabinet, screwheads, metal overlays, etc.), particularly any exposed metal part having a return path to the chassis. Exposed
metal parts having a return path to the chassis should have a minimum resistance reading of  megohm. Any resistance be-
low this value indicates an abnormality which requires corrective action. Exposed metal parts not having a return path to the
chassis will indicate an open circuit.
2. Hot check
Use the circuit in figure to perform this test.
() With switch S open, connect the projector to the measuring circuit. Immediately after connection, measure the leakage
current using both positions of switch S, and with the switching devices in the projector in all of their operating positions.
() Switch S is then closed, energizing the projector. Immediately after closing the switch, measure the leakage current us-
ing both positions of switch S, and with the switching devices in the projector in all of their operating positions. Current
measurements of items () and () are to be repeated after the projector has reached thermal stabilization. The leakage
current must not be more than 0.5 milliampere.
AC 100 to 240 V
Europe, other than USA
NOTICE: Observe all cautions and safety related notes located inside the cabinet and on the chassis.
Warning
. An isolation transformer should be used between the projector and the AC supply point before any test/service is performed
on a LIVE chassis projector.
. Operation of this projector outside the cabinet or with the cover removed, involves a shock hazard from the projector power
supplies. Work on the projector should not be attempted by anyone who is not thoroughly familiar with precautions neces-
sary when working on high voltage equipment.
3. When service is required, observe the original lead dressing. Extra precaution should be given to assure correct lead dress-
ing in the high voltage area. Where a short-circuit has occurred, replace those components that indicate evidence of over-
heating.
Leakage current cold check
Before returning the projector to the customer, it is recommended that leakage current be measured according to the following
methods.
With the AC plug removed from the AC source, place a jumper across the two AC plug prongs. Turn the projector AC switch on.
Using an 500 V D.C. Insulation Tester, connect one lead to the jumpered AC plug and touch the other lead to each exposed met-
al part (screwheads, etc.), particularly any exposed metal part having a return path to the chassis. Exposed metal parts having a
return path to the chassis should have a minimum resistance reading of 4 megohm. Any resistance below this value indicates an
abnormality which requires corrective action.
S2
V
S1
Grounding supply conductor
Projector
GH
(grounding)
open
B
Figure
-  -
AC milliammeter
A
Insulating table