Safety Instructions, Warnings, And Notes - Philips 42PF9945 Service Manual

EN 4 2.

2. Safety Instructions, Warnings, and Notes

2.1
Safety Instructions
Safety regulations require that during a repair:
•
Connect the set to the mains via an isolation transformer (>
800 VA).
Replace safety components, indicated by the symbol h,
•
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.
Safety regulations require that after a repair, the set must be
returned in its original condition. Pay in particular attention to
the following points:
•
Route the wire trees correctly and fix them with the
mounted cable clamps.
•
Check the insulation of the mains lead for external
damage.
•
Check the strain relief of the mains cord for proper function.
•
Check the electrical DC resistance between the mains plug
and the secondary side (only for sets which have a mains
isolated power supply):
1. Unplug the mains cord and connect a wire between the
two pins of the mains plug.
2. Set the mains switch to the "on" position (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 on the set. The reading should be
between 4.5 Mohm and 12 Mohm.
4. Switch "off" the set, and remove the wire between the
two pins of the mains plug.
•
Check the cabinet for defects, to avoid touching of any
inner parts by the customer.
2.2
Warnings
•
All ICs and many other semiconductors are susceptible to
electrostatic discharges (ESD w). 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 same potential.
Available ESD protection equipment:
–
Complete kit ESD3 (small tablemat, wristband,
connection box, extension cable and earth cable) 4822
310 10671.
–
Wristband tester 4822 344 13999.
•
Be careful during measurements in the high voltage
section.
•
Never replace modules or other components while the unit
is switched "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.
2.3
Notes
2.3.1
General
•
In order to prevent damage to ICs and transistors, avoid all
high voltage flashovers.
•
All ICs and many other semiconductors are susceptible to
electrostatic discharges (ESD, w). 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:
FTP1.1E Safety Instructions, Warnings, and Notes
–
Complete kit ESD3 (small tablemat, wristband,
connection box, extension cable and ground cable)
4822 310 10671.
–
Wristband tester 4822 344 13999.
•
Never replace modules or other components while the unit
is 'on'.
•
Measure the voltages and waveforms with regard to the
chassis (= tuner) ground (H), or hot ground (I), 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 (D) and without (E) aerial signal. Measure the
voltages in the power supply section both in normal
operation (G) and in standby (F). These values are
indicated by means of the appropriate symbols.
•
The semiconductors indicated in the circuit diagram and in
the parts lists, are interchangeable per 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.