AV-25L33
AV-25L33B
SAFETY PRECAUTIONS
1. The design of this product contains special hardware, many circuits8. When service is required, observe the original lead dress. Extra
and components specially for safety purposes. For continued pro-precaution should be given to assure correct lead dress in the high
tection, no changes should be made to the original design unlessvoltage circuit area. Where a short circuit has occurred, those com-
authorized in writing by the manufacturer. Replacement parts mustponents that indicate evidence of overheating should be replaced.
be identical to those used in the original circuits. Service should beAlways use the manufacturer's replacement components.
performed by qualified personnel only.
9. Isolation Check
2. Alterations of the design or circuitry of the products should not be(Safety for Electrical Shock Hazard)
made. Any design alterations or additions will void the manufactur-After re-assembling the product, always perform an isolation check
er's warranty and will further relieve the manufacturer of responsi-on the exposed metal parts of the cabinet (antenna terminals, video/
bility for personal injury or property damage resulting therefrom.audio input and output terminals, Control knobs, metal cabinet, screw
heads, earphone jack, control shafts, etc.) to be sure the product is
3. Many electrical and mechanical parts in the products have specialsafe to operate without danger of electrical shock.
safety-related characteristics. These characteristics are often not(1) Dielectric Strength Test
evident from visual inspection nor can the protection afforded byThe isolation between the AC primary circuit and all metal parts
them necessarily be obtained by using replacement componentsexposed to the user, particularly any exposed metal part having a
rated for higher voltage, wattage, etc. Replacement parts which havereturn path to the chassis should withstand a voltage of 3000V AC
these special safety characteristics are identified in the parts list of(r.m.s.) for a period of one second.
Service manual. Electrical components having such features are(. . . . Withstand a voltage of 1100V AC (r.m.s.) to an appliance rated
identified by shading on the schematics and by (!) on the partsup to 120V, and 3000V AC (r.m.s.) to an appliance rated 200V or
list in Service manual. The use of a substitute replacement whichmore, for a period of one second.)
does not have the same safety characteristics as the recommendedThis method of test requires a test equipment not generally found in
replacement part shown in the parts list of Service manual maythe service trade.
cause shock, fire, or other hazards.(2) Leakage Current Check
Plug the AC line cord directly into the AC outlet (do not use a line
4. Don't short between the LIVE side ground and ISOLATED (NEU-isolation transformer during this check.). Using a "Leakage Current
TRAL) side ground or EARTH side ground when repairing.Tester", measure the leakage current from each exposed metal part
Some model's power circuit is partly different in the GND. The differ-of the cabinet, particularly any exposed metal part having a return
ence of the GND is shown by the LIVE : ( ) side GND, the ISO-path to the chassis, to a known good earth ground (water pipe, etc.).
LATED (NEUTRAL) : ( ) side GND and EARTH : ( ) side GND.Any leakage current must not exceed 0.5mA AC (r.m.s.).
Don't short between the LIVE side GND and ISOLATED (NEUTRAL)However, in tropical area, this must not exceed 0.2mA AC (r.m.s.).
side GND or EARTH side GND and never measure the LIVE sideI Alternate Check Method
GND and ISOLATED (NEUTRAL) side GND or EARTH side GNDPlug the AC line cord directly into the AC outlet (do not use a line
at the same time with a measuring apparatus (oscilloscope etc.).isolation transformer during this check.). Use an AC voltmeter hav-
If above note will not be kept, a fuse or any parts will be broken.ing 1000 ohms per volt or more sensitivity in the following manner.
Connect a 1500O 10W resistor paralleled by a 0.15?F AC-type ca-
5. If any repair has been made to the chassis, it is recommended thatpacitor between an exposed metal part and a known good earth
the B1 setting should be checked or adjusted (See ADJUSTMENTground (water pipe, etc.). Measure the AC voltage across the resis-
OF B1 POWER SUPPLY).tor with the AC voltmeter. Move the resistor connection to each ex-
posed metal part, particularly any exposed metal part having a re-
6. The high voltage applied to the picture tube must conform with thatturn path to the chassis, and measure the AC voltage across the
specified in Service manual. Excessive high voltage can cause anresistor. Now, reverse the plug in the AC outlet and repeat each
increase in X-Ray emission, arcing and possible component dam-measurement. Any voltage measured must not exceed 0.75V AC
age, therefore operation under excessive high voltage conditions(r.m.s.). This corresponds to 0.5mA AC (r.m.s.).
should be kept to a minimum, or should be prevented. If severeHowever, in tropical area, this must not exceed 0.3V AC (r.m.s.).
arcing occurs, remove the AC power immediately and determineThis corresponds to 0.2mA AC (r.m.s.).
the cause by visual inspection (incorrect installation, cracked or
melted high voltage harness, poor soldering, etc.). To maintain theAC VOLTMETER
proper minimum level of soft X-Ray emission, components in the(HAVING 1000&/V,
high voltage circuitry including the picture tube must be the exactOR MORE SENSITIVITY)
replacements or alternatives approved by the manufacturer of the
complete product.
7. Do not check high voltage by drawing an arc. Use a high voltage0.15?F AC-TYPE
meter or a high voltage probe with a VTVM. Discharge the picture
tube before attempting meter connection, by connecting a clip leadPLACE THIS PROBE
to the ground frame and connecting the other end of the lead through
ON EACH EXPOSED
a 10kO 2W resistor to the anode button.1500& 10WMETAL PART
GOOD EARTH GROUND
No. 520353 |
ACEC
