Philips 28PW9618, Руководство по обслуживанию

Страница: 5 / 172

Safety and Maintenance Instructions, Warnings, and Notes
EN 5 EM6E 2.
2.
Safety and Maintenance Instructions, Warnings, and Notes
2.1
Safety Instructions
Safety regulations require that during a repair:
•
Due to the chassis concept, a very large part of the circuitry
(incl. deflection) is 'hot'. Therefore, connect the set to the
mains via an isolation transformer.
•
Replace safety components, indicated by the symbol

,
only by components identical to the original ones. Any
other component substitution (other than original type) may
increase risk of fire or electrical shock hazard.
•
Wear safety goggles when you replace the CRT.
Safety regulations require that after a repair, you must return
the set in its original condition. Pay, in particular, attention to
the following points:
•
General repair instruction: as a strict precaution, we advise
you to re-solder the solder connections through which the
horizontal deflection current is flowing. In particular this is
valid for the:
1.
Pins of the line output transformer (LOT).
2.
Fly-back capacitor(s).
3.
S-correction capacitor(s).
4.
Line output transistor.
5.
Pins of the connector with wires to the deflection coil.
6.
Other components through which the deflection current
flows.
Note: This re-soldering is advised to prevent bad connections
due to metal fatigue in solder connections, and is therefore only
necessary for television sets more than two years old.
•
Route the wire trees and EHT cable correctly and secure
them with the mounted cable clamps.
•
Check the insulation of the mains cord for external
damage.
•
Check the strain relief of the mains cord for proper function,
to prevent the cord from touching the CRT, hot
components, or heat sinks.
•
Check the electrical DC resistance between the mains plug
and the secondary side (only for sets that have an isolated
power supply). Do this as follows:
1.
Unplug the mains cord and connect a wire between the
two pins of the mains plug.
2.
Turn on the main power switch (keep the mains cord
unplugged!).
3.
Measure the resistance value between the pins of the
mains plug and the metal shielding of the tuner or the
aerial connection of the set. The reading should be
between 4.5 M
Ω
and 12 M
Ω
.
4.
Switch the TV 'off' and remove the wire between the
two pins of the mains plug.
•
Check the cabinet for defects, to prevent the possibility of
the customer touching any internal parts.
2.2
Maintenance Instructions
We recommend a maintenance inspection carried out by
qualified service personnel. The interval depends on the usage
conditions:
•
When a customer uses the set under normal
circumstances, for example in a living room, the
recommended interval is three to five years.
•
When a customer uses the set in an environment with
higher dust, grease, or moisture levels, for example in a
kitchen, the recommended interval is one year.
•
The maintenance inspection includes the following actions:
1.
Perform the 'general repair instruction' noted above.
2.
Clean the power supply and deflection circuitry on the
chassis.
3.
Clean the picture tube panel and the neck of the picture
tube.
2.3
Warnings
•
In order to prevent damage to ICs and transistors, avoid all
high voltage flashovers. In order to prevent damage to the
picture tube, use the method shown in Fig. 2-1, to
discharge the picture tube. Use a high voltage probe and a
multi-meter (position V
DC
). Discharge until the meter
reading is 0 V (after approx. 30 s).
Figure 2-1 Discharge picture tube
•
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
potential as the mass of the set by a wristband with
resistance. Keep components and tools also at this
potential. Available ESD protection equipment:
–
Complete kit ESD3 (small tablemat, wristband,
connection box, extension cable and ground cable)
4822 310 10671.
–
Wristband tester 4822 344 13999.
•
Together with the deflection unit and any multi-pole unit,
flat square picture tubes form an integrated unit. The
deflection and the multi-pole units are set optimally at the
factory. We do not recommend adjusting this unit during
repair.
•
Be careful during measurements in the high voltage
section and on the picture tube.
•
Never replace modules or other components while the unit
is 'on’.
•
When you align the set, use plastic rather than metal tools.
This will prevent any short circuits and the danger of a
circuit becoming unstable.
2.4
Notes
2.4.1
General
•
Measure the voltages and waveforms with regard to the
chassis (= tuner) ground (symbol

), or hot ground (symbol

), depending on the tested area of circuitry.
•
The voltages and waveforms 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 475.25 MHz (PAL) or 61.25 MHz (NTSC, channel 3).
•
Where necessary, measure the waveforms and 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.
V
CL96532156_040.eps
140501