Note On Electrostatic Shielding; Safety Precaution; X-Ray Radiation Precaution - Loewe CAL 2323 MB Service Manual

CAUTION:
These servicing instructions are for use by qualified service
personal only. To reduce the risk of electric shock do not per-
form any servicing other then that contained in the operating
instructions unless you are qualified to do so:

Note on electrostatic shielding

1. Electrostatically shielded MOS workstations
Components sensitive to electrostatic discharge must be
handled at workstation with electrostatic shielding. An elec-
trostatically shielded MOS workstation is fitted with discharge
resistor which earth all conductive materials, including the
technician working there. Dielectrics are discharged by air
ionisation. The use of soldering irons and measuring equip-
ment at shielded workstation is only possible in conjunction
with isolating transformer in each of the devices used. Meas-
uring equipment chassis are also earthed with discharge re-
sistors.
2. Shielded packaging using conductive materials
To protect against electrostatic charges, electrically conduc-
tive plastics are used for packaging and transport purposes.
Conductive plastics are available in the form of transparent
protective bags, foam plastic, film sheeting or containers.
Sensitive components requiring the use of protective pack-
aging must only be packed and unpacked at shielded work-
stations.
Safety instructions
Warning: Before servicing this chassis, read the "X-ray radi-
ation precaution", "Safety precaution" and "Product safety no-
tice" instructions below.

X-ray radiation precaution

1. Excessive high voitage can produce potentially hazardous
X-RAY RADIATION. To avoid such hazards, the high voltage
must not be above the specified limit. The nominal value of
the high voltage of this TV receiver is
current (minimum brightness) under a 120V AC power source.
The high voltage must not, under any circumstances, exceed
kV.
ß
Refer to table-1 for high voltage ,
0
(See Adjustments procedures on page 1-13)
Each time a TV receiver requires servicing, the high voltage
should be checked following the HIGH VOLTAGE CHECK pro-
cedure in this manual. It is recommended that the reading of
the high voltage be recorded as a part of the service record.
It is important to use an accurate and reliable high voltage
meter.
2. This TV receiver is equipped with a Fail Safe (FS) circuit which
prevents the receiver from producing an excessively high volt-
age even if the UB voltage increases abnormally.
3. The only source of X-RAY RADIATION in this TV receiver is
the picture tube. For continued X-RAY RADIATION protec-
tion, the replacement tube must be exactly the same type
tube as specified in the parts list.
4. Some part in this TV receiver have special safety-related char-
acteristics for X-RAY RADIATION protection For continued
safety, parts replacement should be undertaken only after
referring to the PRODUCT SAFETY NOTICE below.

Safety precaution

Warning: Service should not be attempted by anyone unfamiliar
with the necessary precautions on this receiver. The fol-lowing
are the necessary precautions to be observed before servicing
this chassis.
1. An isolation Transformer should be connected in the power
line between the TV receiver and the AC line before any serv-
ice is performed on the TV receiver.
2. Always discharge the picture tube anode to the CRT con-
ductive coating before handling the picture tube. The picture
tube is highly evacuated and if broken, glass fragments will
be violently expelled. Use shatter proof goggles and keep
picture tube away from the unprotected body while handling.
3. When replacing a chassis in the cabinet, always be certain
that all the protective devices are put back in place, such as;
non-metallic control knobs, insulating covers, shields, isola-
tion resistor-capacitor network etc.
4. The regulations of the country concerned must also be ob-
served.
Leakage current cold check
1. Unplug the AC cord and connect a jumper between the two
kV at zero beam prongs of the plug.
0
2. Turn on the receiver's power switch.
3. Measure the resistance value with an ohmmeter, between
the jumpered AC plug and each exposed metallic cabinet part
on the receiver, such as screw heads, aerials, connectors,
.
ß
control shafts etc. When the exposed metallic part has a re-
turn path to the chassis the reading should be between 4 MΩ
and 20 MΩ. When the exposed metal does not have are turn
path to the chassis the reading must be infinite.
Leakage current hot check
1. Before returning the set to the customer, always perform an
2. Connect a 2000 ohm 10 watt resistor, paralleled by a 0,15µF,
Place this probe
on each exposed
metallic parts.
Product safety notice
Many electrical and mechanical parts in this chassis have spe-
cial safety-related characteristics. These characteristics are
often passed unnoticed by a visual inspection and the protec-
tion afforded by them cannot necessarily be obtained by us-
ing replacement components rated for higher voltage, watt-
age. etc Replacement parts which have these special safety
characteristics are identified in this manual and its supple-
ments; electrical components having such features are identi-
fied by the international hazard symbols "
matic diagram and the parts list.
Before replacing any of these components, read the parts list
in this manual carefully The use of substitute replacement parts
which do not have the same safety characteristics as speci-
fied in the parts list may create shock fire X-ray radiation or
other hazards.
1 - 3
AC leakage current check on the exposed metallic parts of
the cabinet, such as antennas, temminals, screwheads, met-
al overlays, control shafts etc to be sure the set is safe to
operate without danger of electrical shock Plug the AC line
cord directly into a 120V AC outlet (do not use a line isolation
transformer during this check) Use an AC voltmeter having
5000 ohms per volt or more sensitivity in the following man-
ner:
AC type capacitor, between a known good earth ground (wa-
ter pipe, conduit, etc.) and the exposed metallic parts, one at
a time (Fig. 1). Measure the AC voltage across the combina-
tion of 2000 ohm resistor and 0,15µF capacitor. Reverse the
AC plug at the AC outlet and repeat AC voltage measure-
ments for each exposed metallic part. Voltage measured must
not exceed 0,5 volts rms. This corresponds to 0,25 milliamp.
AC. Any value exceeding this limit constitutes a potential shock
hazard and must be corrected immediately.
AC leakage current hot check circuit
AC Voltmeter
0,15µF
2000 ohm
10 watt
Good earth
ground such
as a water
pipe,
conduit,
etc.
Fig. 1
" on the sche-