Safety & Maintenance Instructions, Warnings, and Notes
GB 5
L01.1E
2.
2. Safety & Maintenance Instructions, Warnings, and Notes
2.1
Safety Instructions For Repairs
Safety regulations require that during a repair:
•
Due to the ‘hot’ parts of this chassis, the set must be
connected to the AC power via an isolation transformer.
•
Safety components, indicated by the symbol
, should
be replaced by components identical to the original ones.
•
When replacing the CRT, safety goggles must be worn.
Safety regulations require that after a repair, the set must be
returned in its original condition. Pay 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:
–
all pins of the line output transformer (LOT)
–
fly-back capacitor(s)
–
S-correction capacitor(s)
–
line output transistor
–
pins of the connector with wires to the deflection coil
–
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 AC power cord for external
damage.
•
Check the strain relief of the AC power cord for proper
function, to prevent the cord from touching the CRT, hot
components, or heat sinks.
•
Check the electrical DC resistance between the AC plug
and the secondary side (only for sets that have an
isolated power supply). Do this as follows:
1. Unplug the AC power cord and connect a wire
between the two pins of the AC plug.
2. Turn on the main power switch (keep the AC power
cord unplugged!).
3. Measure the resistance value between the pins of
the AC plug and the metal shielding of the tuner or
the aerial connection of the set. The reading should
be between 4.5 M
W
and 12 M
W
.
4. Switch the TV OFF and remove the wire between the
two pins of the AC plug.
•
Check the cabinet for defects, to prevent the possibility of
the customer touching any internal parts.
2.2
Maintenance Instructions
It is recommended to have a maintenance inspection carried
out by qualified service personnel. The interval depends on
the usage conditions:
•
When the set is used under normal circumstances, for
example in a living room, the recommended interval is
three to five years.
•
When the set is used 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 VDC). Discharge until the meter
reading is 0 V (after approx. 30 s).
Figure 2-1
•
All ICs and many other semiconductors are susceptible
to electrostatic discharges (ESD)
. Careless handling
during repair can reduce life drastically. When repairing,
make sure that 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. Adjustment of this unit during repair is therefore
not recommended.
•
Be careful during measurements in the high voltage
section and on the picture tube.
•
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.
2.4
Notes
•
Measure the voltages and waveforms with regard to the
chassis (= tuner) ground (
), or hot ground (
),
depending on the area of circuitry being tested.
•
The voltages and waveforms shown in the diagrams are
indicative. Measure them in the Service Default Mode
(see chapter 5) with a color 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 (
) and without (
) aerial signal. Measure the
voltages in the power supply section both in normal
operation (
) and in standby (
). These values are
indicated by means of the appropriate symbols.
•
The picture tube panel has printed spark gaps. Each
spark gap is connected between an electrode of the
picture tube and the Aquadag coating.
•
The semiconductors indicated in the circuit diagram and
in the parts lists are completely interchangeable per
position with the semiconductors in the unit, irrespective
of the type indication on these semiconductors.
V
CL 26532098/042
140792
