Philips 27VM34 U Service Manual page 5

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).
• All ICs and many other semiconductors are susceptible to electrostatic discharges
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)
– 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 (
voltages in the power supply section both in normal operation (
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.
Figure 2-1
) and without (
) and in standby (
5--60
(ESD)_ Careless handling
),
) aerial signal. Measure the
). These values are