Philips 202P4, Service Manual

Page: 17 / 121

17
Warning and Notes
202P4 M25P
1. Safety Instructions for Repairs
2. Maintenance Instructions
3. Warnings
1.1 Safety regulations require that during a repair:
- The set should be connected to the mains via an isolating
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.
1.2 Safety regulations require also that after a repair:
- The set should be returned in its original condition.
- The cabinet should be checked for defects to avoid touching,
by the customer, of inner parts.
- The insulation of the mains lead should be checked for
external damage.
- The mains lead strain relief should be checked on its
function.
- The cable form and EHT cable are routed correctly and fixed
with the mounted cable clamps in order to avoid touching of
the CRT, hot components or heat sinks.
* Thermally loaded solder joints should be checked and
resoldered where necessary. This includes components like
LOT, the line output transistor, fly-back capacitor.
It is recommended to have a maintenance inspection carried out
periodically by a qualified service employee. The interval depends on
the usage conditions.
- During the maintenance inspection the above mentioned "safety
instructions for repair" should be carried out The power supply and
deflection circuitry on the chassis, the CRT panel and the neck of
the CRT should be cleaned.
When cleaning the monitor on the outside:
- Always disconnect the monitor from the mains.
- Always use a damp AND NOT WET lint-free cloth.
- To clean the screen, apply a household glass cleaner to a cloth and
then wipe the screen.
- Do not use solvents or abrasives on the monitor.
It might discolour the cabinet and/or affect the anti glare treatment
on your screen.
3.1 In order to prevent damage to ICs and transistors, all high-
voltage flash-overs must be avoided. In order to prevent damage to
the picture tube, the method shown in Fig 3.1 should be used to
discharge the picture tube. Use a high-voltage probe and a
multimeter (position DC-V). Discharge until the meter reading is 0V
(after approx 30s).
3.3 Be careful when taking measurements in the high-voltage section
3. 2 ESD
All ICs and many other semiconductors are sensitive to electrostatic
discharges (ESD). Careless handling during repair can drastically
shorten the life. Make sure that during repair you are connected by a
pulse band with resistance to the same potential as the earth of the
unit. Keep components and tools also at this same potential.
and on the picture tube panel.
3.4 Never replace modules or other components while the unit is
switched on.
3.5 When making settings, use plastic rather than metal tools.
This will prevent any short-circuit and the danger of a circuit
becomes unstable.
3.6 After repair the wiring should be fastened once more in the cable
clamps for this purpose.
3.7 Together with the deflection unit the picture tube is used as an
integrated unit. Adjustment of this unit during repair is therefore
not recommended.
The semiconductors indicated in the circuit diagram(s) and in the
parts lists are completely interchangeable per position with the
semiconductors in the unit, irrespective of the type indication on
these semiconductors.
4. Notes
Fig. 3.1
V
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