Servicing; Safety And Service Guidelines; Ac Leakage Test; And Zvm-135 Controls And Connectors. 11 3. Zvm-133 And Zvm-136 Controls And Connectors. 12 4. Ac Leakage Voltmeter Circuit - Zenith ZVM-131 Service Manual

Servicing
Safety and Service Guidelines
WARNING: No work should be attempted on any part of
the chassis by anyone not familiar with Zenith service pro-
cedures and precautions; otherwise, personal injury may
result.
WARNING: With the monitor power turned off and discon-
nected, discharge the high voltage anode lead at the CRT
using a jumper lead connected between the chassis and
a screwdriver (see Figure 32). Failure to comply could re-
sult in severe shock and/or personal injury.
WARNING: Do not operate the monitor with excessive
high voltage any longer than necessary or the monitor may
produce X-rays from the CRT.
Excessive high voltage will produce X-rays from the CRT;
always verify that the voltage is at normal levels when ser-
vicing the monitor.
WARNING: Carefully handle the cathode-ray tube when
you hold, remove, or install it; otherwise, implosion and/or
injury may result.
NOTE: Under no circumstances should the original design
be modified or altered without permiSSion from Zenith Elec-
tronics Corporation.
AC Leakage Test
To prevent electrical shock after reassembly, perform an
AC leakage test on all exposed metal parts of the monitor.
Do
not use an isolation transformer to perform this test.
1. Connect the test circuit as shown in Figure 4.
2. With the monitor turned on, measure the leakage
voltage between earth ground and an exposed moni-
tor metal part.
3. Repeat the measurement with the meter leads re-
versed.
4. Repeat steps 2 and 3 until all exposeq metal parts
are verified to have satisfactory AC leakage levels.
WARNING: Any leakage voltage measurement that ex-
ceeds 0.75 volts rms (0.5 milliamperes AC) constitutes a
potential shock hazard and must be corrected.
CAUTION: Some of the ICs (integrated circuits) used in
the monitor are electrostatic-sensitive devices (ESO).
These circuits can be damaged by static electricity. When
handling any IC, use a wrist grounding strap or be sure to
equalize the static charge before touching the IC.
A.C. VOLTMETER
(5KOHM/VOL T MINIMUM)
Page 18
ICLI
HE- 22-4384
.15jJF
A.C. TYPE
HE-
TO GOOD EARTH GROUND 63-10401-76
SUCH AS WATER PIPE,
CONDUIT, ETC.
1500n
10 WATT
PLACE THIS PROBE
ON EACH EXPOSED
METALLIC PART.
Figure 4
AC Leakage Voltmeter Circuit