Panasonic TX-PR65VT20, Service Manual

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1 Safety Precautions
1.1. General Guidelines
6
1.2.
1. W h e n co n d u ctin g repairs and servicing, do not a tte m p t to m od ify th e equipm en t, its parts o r its m aterials.
2. W h e n w irin g units (w ith cables, fle xib le cab le s o r lead w ire s ) are sup plied as rep air parts and on ly one w ire o r som e o f th e
w ire s have been broken o r discon necte d, do not a tte m p t to rep air o r re-w ire th e units. R e pla ce th e en tire w irin g unit instead.
3. W h e n c on du cting repairs and servicing, do not tw is t the F asten co n n e cto rs but plug th e m stra ig h t in o r unplug th e m straig ht
out.
4. W h e n servicing, ob serve th e origin al lead dress. If a sh o rt circu it is found, replace all parts w h ich have been o ve rhe ated or
da m ag ed by the sh o rt circuit.
5. A fte r servicing, see to it th a t all th e pro te ctive de vice s such as in sulation barriers, in sula tion papers shield s are p ro pe rly
installed.
A fte r servicing, m ake th e fo llo w in g le akage c u rre n t che cks to p re ve n t th e c u s to m e r fro m being exposed to s h o c k hazards.
Touch-Current Check
1. Plug th e A C cord directly into th e A C outlet. Do not use an isolation tra n s fo rm e r fo r th is check.
2. C o n n e c t a m ea surin g n e tw o rk fo r to u ch curre nts betw een each exp ose d m etallic part on th e set and a good earth ground
such as a w a te r pipe, as sho w n in F igure 1.
3. U se Le aka ge C u rre n t T ester (S im pson 228 o r e q u iv a le n t) to m ea sure th e po tential acro ss th e m ea surin g network.
4. C h e c k each exp ose d m etallic part, and m ea sure th e v o lta g e at each point.
5. R e serve th e A C plug in th e A C o u tle t and rep ea t each o f th e ab o ve m easure.
6. T he po tential at any po in t (T O U C H C U R R E N T ) e xp resse d as v o lta g e U
1
and U
2
, does not exce ed th e fo llo w in g values:
F or a. c.: U
1
= 35 V (pe ak) and U
2
= 0.35 V (peak);
F or d. c.: U 1 = 1.0 V,
Note:
T he lim it v a lu e o f U
2
= 0.35 V (pe ak) fo r a. c. and U
1
= 1.0 V fo r d. c. c orre spo nd to th e v a lu e s 0.7 m A (pe ak) a. c. and 2.0
m A d. c.
T he lim it va lu e U
1
= 35 V (pe ak) fo r a. c. corre spo nd to th e va lu e 70 m A (pe ak) a. c. fo r fre q u e n c ie s g re a te r tha n 100 kHz.
7. In case a m e a s u re m e n t is out o f the lim its specified, th e re is a po ssib ility o f a s h o c k hazard, and th e e q u ip m e n t should be
repaired and rech ecke d be fore it is returned to th e custom er.
Measuring network for TOUCH CURRENTS
COLD
WATER PIPE
(EARTH GROUND)
Rs=
1500Q
_ L Cs=
0.22|
j
F
10kQ
-1
k 1 -------
1
Ro=
----------------
J
500Q
'
U
1
=
r
= 0.022|
j
F ( V ) JQ LjJ JUUii U
1
—|— и.и^гф Г ^ V
J
| U
2
(V)
APPLIANCES
EXPOSED
METAL PARTS
Resistance values in ohms (Q)
V: Voltmeter or oscilloscope
(r.m.s. or peak reading)
Input resistance: > 1 MQ
Input capacitance: < 200 pF
Frequency range: 15 Hz to 1 MHz and d.c. respectively
NOTE - Appropriate measures should be taken to obtain the correct value in case of non-sinusoidal waveforms.
Figure 1
3