Philips 28PW9528, Руководство по обслуживанию

Страница: 5 / 134

Safety Instructions, Warnings, and Notes
EN 5 EM5.1E 2.
2.
Safety Instructions, Warnings, and Notes
2.1
Safety Instructions
Safety regulations require that during a repair:
•
Connect the Receiver box to the Mains via an isolation
transformer.
•
When you use the Receiver box in combination with a
plasma monitor, do not operate the monitor without the
front glass plate. One function of this glass plate is to
absorb IR radiation. Without this glass plate, the level of
radiation could damage your eyes.
•
Safety components, indicated by the symbol

, must be
replaced with original components.
Safety regulations require that after a repair, you must return
the set in its original condition. Pay particular attention to the
following points:
•
Route the wire trees in their original positions and fix them
in place with the mounted cable clamps.
•
Check the insulation of the Mains cord for external
damage.
•
Check the electrical DC resistance between the Mains plug
and the secondary side (only for sets which have a Mains
isolated power supply):
–
Unplug the Mains cord and connect a wire between the
two pins of the Mains plug;
–
Set the Mains switch to the "on" position (keep the
Mains cord unplugged!).
–
Measure the resistance value between the pins of the
Mains plug and the metal shielding of the tuner or the
aerial connection on the set. The reading should be
between 4.5 Mohm and 12 Mohm.
–
Set the Mains switch to the "off" position, and remove
the wire between the two pins of the Mains plug.
•
Check the cabinet for defects, to prevent the customer from
touching any inner parts of the television set.
2.2
Warnings
•
All ICs and many other semiconductors are susceptible to
electrostatic discharges (ESD symbol

). Careless
handling during repair can reduce life drastically. Make
sure that, during repair, you are connected with the same
electrical potential as the set by a wristband with
resistance. Keep components and tools at this same
potential. Available ESD protection equipment:
–
Complete ESD3 kit (small tablemat, wristband,
connection box, extension cable and earth cable):
4822 310 10671.
–
Wristband tester: 4822 344 13999.
•
Be careful while taking measurements in the live voltage
section.
•
Never replace modules, or other components, with the
television set "'ON."
•
Use plastic tools, instead of metal tools, when performing
alignments on the television set. This will help prevent
short circuits and reduce the danger of a circuit becoming
unstable.
2.3
Notes
2.3.1
General
•
Measure the direct voltages and oscillograms with regard
to the chassis ground (symbol

), or hot ground
(symbol

).
•
The direct voltages and oscillograms shown in the
diagrams are indicative. Measure them in the Service
Default Mode (see chapter 5) with a colour bar signal and
stereo sound (L: 3 kHz, R: 1 kHz unless stated otherwise)
and picture carrier at 61.25 MHz (NTSC).
•
Where necessary, measure the oscillograms and direct
voltages with (symbol

) and without (symbol

) aerial
signal. Measure the voltages in the power supply section
both in normal operation (symbol

) and in standby
(symbol

). These values are indicated by means of the
appropriate symbols.
•
The semiconductors indicated in the circuit diagram and in
the parts lists, are interchangeable position with the
semiconductors in the unit, irrespective of the type
indication on these semiconductors.
2.3.2
Schematic Notes
•
All resistor values are in ohms and the value multiplier is
often used to indicate the decimal point location (e.g. 2K2
indicates 2.2 kohm).
•
Resistor values with no multiplier may be indicated with
either an 'E' or an 'R' (e.g. 220E or 220R indicates 220
ohm).
•
All Capacitor values are expressed in Micro-Farads
(
µ
= x10
-6
), Nano-Farads (n = x10
-9
), or Pico-Farads
(p = x10
-12
).
•
Capacitor values may also use the value multiplier as the
decimal point indication (e.g. 2p2 indicates 2.2 pF).
•
An 'asterisk' (*) indicates component usage varies. Refer to
the diversity tables for the correct values.
•
The correct component values are listed in the Electrical
Replacement Parts List. Therefore, always check this list
when there is any doubt.
2.3.3
Practical Service Precautions
•
It makes sense to avoid exposure to electrical shock.
While some sources are expected to have a possible
dangerous impact, others of quite high potential are of
limited current and are sometimes held in less regard.
•
Always respect voltages. While some may not be
dangerous in themselves, they can cause unexpected
reactions - reactions that are best avoided. Before reaching
into a powered TV set, it is best to test the high voltage
insulation. It is easy to do, and is a good service precaution.
•
Before powering up the TV set with the rear cover off
(or on a test fixture), attach a clip lead to the CRT DAG
ground and to a screwdriver blade that has a well insulated
handle. After the TV is powered on and high voltage has
developed, probe the anode lead with the blade, starting at
the case of the High Voltage Transformer (flyback - IFT).
Move the blade to within two inches of the connector of the
CRT. If there is an arc, you found it the easy way,
without getting a shock! If there is an arc to the
screwdriver blade, replace the part that is causing the
problem: the High Voltage Transformer or the lead (if it is
removable).