Advertisement
Important Service Notes
1. X-ray Radiation Rrecaution
1) Excessive high voltage can produce potentially hazardous X-RAY RADIA-
TION. To avoid such hazards, the high voltage must not be above the spec-
ified limit. The nominal value of the high voltage of this receiver is
25.5kv(20" /21" ) & 23.5kv(14" )at zero beam current (minimum brightness)
under a 120V/220V AC power source. The high voltage must not, under any
circumstances, exceed 28kv(20" /21" ) & 26kv(14" ). Each time a receiver
requires servicing, the high voltage should be checked following the HIGH
VOLTAGE CHECK procedure on page 10 of this manual. It is recom-
mended as a parts of the service record. It is important to use an accurate
and reliable high voltage meter.
2) This receiver is equipped with X-RADIATION PROTECTION circuit which
prevents the receiver from producing an excessively high voltage even if the
B+voltage increases abnormally. Each time the receiver is serviced, X-
RADIATION PROTECTION circuit must be checked to determine that the
circuit is properly functioning, following the X-RADIATION PROTECTION
CIRCUIT CHECK procedure on page 6 of this manual.
3) The only source of X-RAY RADIATION in this TV receiver is the picture tube.
For continued X-RAY RADIATION protection, the replacement tube must be
exactly the same type tube as specified in the parts list.
4) Some parts in this receiver have special safety-related characteristics for X-
RAY RADIATION protection. For continued safety, parts replacement
should be undertaken only after referring to the PRODUCT SAFETY
NOTICE below.
2. Safety Precaution
WARNING: Service should not be attempted by anyone unfamiliar with the
necessary precaution on this receiver. The following are the necessary precau-
tion to be observed before servicing.
1) Since the chassis of this receiver has hazardous potential to ground when-
ever the receiver is plugged in (floating chassis), an isolation transformer
must be used during servicing to avoid shock hazard.
2) Always discharge the picture tube anode to the CRT conductive coating the
picture tube. The picture tube is highly evacuated and if broken, glass frag-
ments will be violently expelled. Use shatterproof goggles and keep picture
tube away from the body while handling.
3) When placing chassis in the cabinet, always be certain that all the protective
devices are put back in place, such as; nonmetallic control knobs, insulat-
ing covers, shields, isolation resistor-capacitor network, etc.
4) Before returning the set to the customer, always perform an AC leakage cur-
rent check on the exposed metallic parts of the cabinet, such as antennas,
terminals, screw-heads, metal 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 sensi-
tivi-ty in the following manner.
Connect at 1500 ohm 10 watt resistor, paralleled by a 0.15 mfd. AC type
capacitor, between a known good earth ground (water pipe, conduit etc.)
and the exposed metallic parts, one at a time. Measure the AC voltage
across the combination of 1500 ohm resistor and 0.15 mfd capacitor. Volt-
age measured must not exceed 0.3 volts RMS. This corresponds to 0.2 mill-
liamp. AC. Any value exceeding the limit constitutes a potential shock
hazard and must be corrected immediately.
AC VOLT METER
Good earth ground
such as d water
pipe, conduit, etc.
3. Product Safety Notice
Many electrical and mechanical parts in this chassis have special safety-related
characteristics. These characteristics are often passed unnoticed by a visual
inspection and the protection afforded by them cannot necessarily be obtained
by using replacement components rated for higher voltage, wattage, etc.
Replacement parts which have these special safety characteristics are identi-
fied in this manual and its supplements; electrical components having such fea-
tures are identified by shading on the schematic 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 specified in the parts list may create X-ray radiation or
other hazards.
4. Service Notes
1) When replacing parts or circuit boards, clamp or bend the lead wires to termi-
nals before soldering.
2) When replacing a high wattage resistor (metal oxide film resistor) in the cir-
cuit board, keep the resistor min 1/2 inch away form circuit board.
3) Keep wires away from high voltage or high temperature components.
DAEWOO ELECTRONICS CO., LTD.
C.P.OBOX8003 SEOUL, KOREA
Tel : 82-2-360-7798
Fax : 82-2-360-7877
E-mail : G7F00E@dwe.web.co.kr
Printed in Apr. 2000
0.15uF
1500 OHM
Place this probe
on each exposed
metallic part.
10WATT
Advertisement
