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1.  It is advisable to insert an isolation transformer in the AC supply before servicing a hot chassis.

2.  When servicing, observe the original lead dress, especially the lead dress in the high voltage 

circuits.

If a short circuit is found, replace all parts which have been overheated or damaged by the 
short circuit.

3.  After servicing, see to it that all the protective devices such as insulation barriers, insulation 

papers, shields, and isolation R-C combinations, are properly installed.

4.  When the receiver is not to be used for a long period of time, unplug the power cord from the 

AC outlet.

5.  Potential, as high as 

30.0kV

 , is present when this monitor is in operation. Operation of the 

Projection Monitor without the rear cover involves the danger of a shock hazard from the 
power supply. Servicing should not be attempted byanyone who is not thoroughly familiar 
with the precautions necessary when working on high voltage equipment. Always discharge 
the anode of the projection tube to the Projection Monitor chassis before handling the tube.

6.  After servicing make the following leakage current checks to prevent the customer from being 

exposed to shock hazards.

 

 

1.  Unplug the AC cord and connect a jumper between the two prongs on the plug.

2.  Turn on the Projection Monitor´s power switch.

3.  Measure the resistance value, with an ohmmeter, between the jumpered AC plug and each 

exposed metallic cabinet part on the projection monitor, such as screw heads, connectors, 
control shafts, etc. When the exposed metallic part has a returnpath to the chassis, the reading 
should be between 4 M

Ω

 and 20 M

Ω

.

When the exposed metal does not have a return path to the chassis, the reading must be

.

 

 

1.  Plug the AC cord directly into the AC outlet. Do not use an isolation transformer for this 

check.

2.  Connect a 2k

Ω

, 10W resistor, in series with an exposed metallic part on the projection monitor 

and an earth such as a water pipe.

3.  Use an AC voltmeter, with high impedance type, to measure the potential across the resistor.

4.  Check each exposed metallic part, and measure the voltage at each point.

5.  Reverse the AC plug in the AC outlet and repeat each of the above measurements.

6.  The potential at any point should not exceed 1.0V rms. In case a measurement is outside of the 

limits specified, there is a possibility of a shock hazard, and the projection monitor should be 
repaired and rechecked before it is returned to thecustomer.

Fig. 1

 

 

 

Warning :

 

1.  The potential sources of X-Radiation in projection monitor are the High Voltage section and 

the projection tube.

2.  When using a projection tube test jig for service, ensure that jig is capable of handling 

30.0kV

 

without causing X-Radiation.

Note:

 

It is important use an accurate periodically calibrated high voltage meter.

1.  Set the brightness to minimum.

2.  Set the service switch to the service position.

3.  Measure the High Voltage. The meter reading should indicate 

30.0 ± 1.0 kV

 . If the meter 

indication is out of tolerance, immediate service and correction is required to prevent the 
possibility of premature component failure.

4.  To prevent an X-Radiation possibility, it is essential to use the specified projection tube.