X-Radiation; Leakage Current Cold Check - Philips 32R5 Service Manual

X-RADIATION

1. Be sure procedures and instructions to all your service personnel cover the subject of
X-radiation. Potential sources of X-rays in TV receivers are the picture tube and the high
voltage circuits. The basic precaution which must be exercised is to keep the high
voltage at the factory recommended level.
2. To avoid possible exposure to X-radiation and electrical shock, only the
manufacturer's specified anode connectors must be used.
3. It is essential that the service technician has an accurate HV meter available at all
times. The calibration of this meter should be checked periodically against a reference
standard.
4. When the HV circuitry is operating properly there is no possibility of an X-radiation
problem. High voltage should always be kept at the manufacturer's rated value - no
higher - for optimum performance. Every time a color set is serviced, the brightness
should be run up and down while monitoring the HV with a meter to be certain that the
HV is regulated correctly and does not exceed the specified value. We suggest that you
and your technicians review test procedures so that HV and HV regulation are always
checked as a standard servicing procedure, and the reason for this prudent routine is
clearly understood by everyone. It is important to use an accurate and reliable HV meter.
It is recommended that the HV reading be recorded on each customer's invoice, which
will demonstrate a proper concern for the customer's safety.
5. When troubleshooting and making test measurements in a receiver with a problem of
excessive high voltage, reduce the line voltage by means of a Variac to bring the HV into
acceptable limits while troubleshooting. Do not operate the chassis longer than necessary
to locate the cause of the excessive HV.
6. New picture tubes are specifically designed to withstand higher operating voltages
without creating undesirable X-radiation. It is strongly recommended that any shop test
fixture which is to be used with the new higher voltage chassis be equipped with one of
the new type tubes designed for this service. Addition of a permanently connected HV
meter to the shop test fixture is advisable. The CRT types used in these new sets should
never be replaced with any other types, as this may result in excessive X-radiation.
7. It is essential to use the specified picture tube to avoid a possible X-radiation problem.
8. Most TV receivers contain some type of emergency "Hold Down" circuit to prevent
HV from rising to excessive levels in the presence of a failure mode. These various
circuits should be understood by all technicians servicing them, especially since many
hold down circuits are inoperative as long as the receiver performs normally.

LEAKAGE CURRENT COLD CHECK

1. Unplug the ac line cord and connect a jumper between the two prongs of the plug.
2. Turn on the power switch.
3. Measure the resistance value between the jumpered ac plug and all exposed cabinet
parts of the receiver, such as screw heads, antennas, and control shafts. When the
exposed metallic part has a return path to the chassis, the reading should be between 1