Sunstech PLF-77TD, Service Manual

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1. SAFETY PRECAUTIONS
Before returning a unit to the customer, always make a safety check
of the entire unit, including, but not limited to the following items:
a. Be sure that no built-in protective devices are defective and/or have
been defeated during servicing.
(1) Protective shields are provided to protect to protect both the
technician and the customer. Correctly replace all missing protective
shields including any removed for servicing convenience.
(2) When reinstalling the chassis and/or other assemblies in the
cabinet, be sure to put back in place all protective devices, including, but
not limited to, nonmetallic control knobs, insulating fishpapers,
adjustment and compartment covers/shields and isolation resistor
capacitor networks. Do not operate this unit of permit it to be operated
without all protective devices correctly installed and functioning.
b. Be sure that there are no cabinet openings through which an adult
or child might be able to insert their fingers and contact a hazardous
voltage. Such openings include, but are not limited to, excessively wide
cabinet ventilation slots, and an improperly fitted and/or incorrectly
secured cabinet back cover.
c. Leakage Current Hot Check - With the unit completely
reassembled, plug the AC line cord directly into a AC outlet. (Do not
use an isolation transformer during this test.) Use a leakage current
tester or a metering system that complies with American National
Standards institute (ANSI) C101.1 “Leakage Current for Appliances”
and Underwriters Laboratories (UL) 1410, (50.7). With the unit AC
switch first in the ON position and then in the OFF position, measure
from a known earth ground (metal water pipe, conduit, etc.) to all
exposed metal parts of the unit (antennas, handle bracket, metal cabinet,
screwheads, metallic overlays, control shaft, ect.), especially any
exposed metal parts that offer an electrical return path to the chassis.
Any current measured must not exceed 0.5 milliamp. Reverse the unit
power cord plug in the outlet and repeat test.
ANY MEASUREMENTS NOT WITHIN THE LIMITS SPECIFIED
HEREIN INDICATE A POTENTIAL SHOCK HAZARD THAT
MUST BE ELIMINATED BEFORE RETURNING THE UNIT TO
THE CUSTOMER.
DEVICE
UNDER
TEST
TEST ALL EXPOSED
METAL SURFACES
AC LEAKAGE TEST
2-WIRE CORD ALSO
TEST WITH PLUG
REVERSED (USING AC
ADAPTER PLUG A
REQUIRED)
LEAKAGE
CURRENT
TESTER
EARTH
GROUND
(READING
SHOULD
NOT BE
ABOVE
0.5mA)
d. Insulation Resistance Test Cold Check
(1) Unplug the power supply cord and connect a jumper wire
between the two prongs of the plug.
(2) Turn on the power switch of the unit.
(3) Measure the resistance with an ohmmeter between the jumpered
AC plug and each exposed metallic cabinet part on the unit, such as
screwheads, antenna, control shaft, handle brackets, etc. When the
exposed metallic part has a return path to the chassis, the reading
should be between 1 and 5.2 Megohm. When there is no return path to
the chassis, the reading must be “infinite”. If it is not within the limits
specified, there is the possibility of a shock hazard, and the unit must
be repaired and rechecked before it is returned to the customer.
2. PRODUCT SAFETY NOTICE
Some electrical and mechanical parts have special safety related
characteristics which are often not evident from visual inspection, nor
can be protection they give necessarily be obtained by replacing them
with components rated for higher voltage, wattage, etc. Parts that have
special safety characteristics are identified by a
¡ I
on schematic and
parts list. Use of a substitute replacement that does not have the same
safety characteristics as the recommended replacement part might create
shock, fire, and/or other hazards. Product Safety is under review
continuously and new instructions are issued whenever appropriate.
3. SERVICING PRECAUTIONS
CAUTION: Before servicing the unit covered by this service manual
and its supplements, read and follow the SAFETY PRECAUTIONS on
this page. NOTE: If unforeseen circumstances create a conflict between
the following servicing precautions and any of the safety precautions,
always follow the safety precautions. Remember: Safety First.
General Servicing Precautions.
a. Always unplug the unit’s AC power cord from the AC power
source before:
(1) removing or reinstalling any component, circuit board, module, or
any other unit assembly.
(2) disconnecting or reconnecting any unit electrical plug or other
electrical connection.
(3) connecting a test substitute in parallel whit an electrolytic
capacitor in the unit.
Caution: A wrong part substitution or incorrect polarity
installation of electrolytic capacitors may result in an explosion hazard.
b. Do not defeat any plug/socket B+ voltage interlocks with which
the unit covered by this service manual might be equipped.
c. Do not apply AC power to this unit and/or any of its electrical
assemblies unless all solid-state device heat sinks are correctly installed.
d. Always connect a test unit ground lead to the unit chassis ground
before connecting the test unit positive lead. Always remove the test
instrument’s ground lead last.
4. LASER PRECAUTIONS
WARNING!
1. When servicing (in case it is necessary to confirm Laser Beam
Emission), be sure not to place your eyes any closer than 1 ft or 30cm
from the surface of the Object Lens on the Optical Pickup Block.
HANDLING THE LASER PICKUP
2. Laser diodes are extremely susceptible to damage from static
electricity. Even if a static discharge does not ruin the diode, it can
shorten its life or cause it to work improperly. When replacing the
pickup, use a conductive mat on the floor and desk and wear a wrist
IMPORTANT SERVICE SAFETY INFORMATION
OM
ANTENNA
TERMINAL
EXPOSED
METAL
PART
OHMMETER