akira PTV-50H08 User manual

Projection TV
Service Manual

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Model No.: PTV-50H08
Version: 1.0
MODEL:
PTV-50H08

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Model No.: PTV-50H08
Version: 1.0
CONTENTS
SAFE NOTICE......................................................................................................................................... 4
SPECIFICATION ..................................................................................................................................... 7
TV SET OVERVIEW............................................................................................................................... 8
MAINTENANCE ADJUSTEMENT ....................................................................................................... 9
NOTICE FOR MAINTENANCE .......................................................................................................... 21
CIRCUIT DIAGRAM ............................................................................................................................ 35

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Model No.: PTV-50H08
Version: 1.0
SAFETY NOTICE
Use an insolating transformer during maintenance.
In this manual and the parts list of its annexed tables as well as the schematic circuit diagram, those
components with special safety functions are marked with “ ! ” need paying special attention upon
maintenance. Maintainers shall carefully read the “Safety Notices” and “Safety Precautions” in the
manual before maintaining the TV set core.
Important: In case the projection tube is replaced, only the same model or an equivalent model certified
by “CB” shall be used to ensure the protection function to the X-ray.
The maintenance of this product is only applicable to the qualified maintenance technicians, which
means that unauthorized maintenances are forbidden. The qualified technicians shall have necessary test
equipment and special tools, and shall have been trained with those complicated products said in this
manual to have the ability to maintain safely such complicated products as the projection TV set said in
this manual.
Improper maintenance may affect the safety and reliability of the product. If you are not qualified to
maintain the product, never take a risk trying to maintain it, find a qualified maintainer to maintain it
instead.
W a r n i n g
When maintain or handles the circuit plank to imply with the other a piece that soldering lead feet,
should avoid the soldering getting in touch with skin directly. At the same time, notice and do not
inhale welding a creation any smoke or airs.
Safety Precautions
1 Check and test the complete TV set maintained for safety before handing it to the costumer. The
items to be checked and tested are as follows:
a. Make sure that the safeguard devices and parts are in good condition, and not removed during
the maintenance.
i. The safeguard devices and parts of this TV set core for protecting the technicians and
costumers shall be all reinstalled properly, including those removed for maintenance
convenience.
ii. Always operate the TV set with all the safeguard devices and parts reinstalled properly
after the reassembly of the TV set core and other assemblies.
iii. Any maintenance negligent of the safety precautions or without safety check and test
may cause dangers.

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Model No.: PTV-50H08
Version: 1.0
b. Make sure there are no gaps with the shell so as to prevent adults and children from putting
fingers inside and touching the dangerous voltage. The gaps include but not limited in:
i. Gaps with the front frame are too large.
ii. The back cover is not installed properly or correctly.
c. Test of antenna cold junction: Connect the two pins of the TV set plug with a piece of
conductor, with the TV set switched on. Connect one end of the ohmmeter to the pin of the plug,
and the other end to the antenna input terminal of the tuner or the bare screw. Connect to the
coaxial cable if possible. If the resistance is less than 8 ohms or greater than 11 ohms,
abnormalities must exist, which shall be removed before the TV set is submitted to the
costumer. Repeat the above test with the TV set switched off.
d. Leakage current test: After the reassembly, insert the mains plug of the TV set into a 40Vsocket
(Do not use an insolating transformer during the test. The test connection is shown in Fig.1.).
Test with a leakage current meter or test system first with the switch on, then with the switch
off. Test the leakage current of the known groundings (metal pipes) to each of the bare metal
parts (the antenna, the knob supports, the metal front frames, the screw ends, the metal covers,
the control buttons, etc.) of the TV set, especially the bare metal parts connected to the core.
None of the currents shall be more than 0.7mA. Repeat the same tests with the polarity of the
plug exchanged. Any leakage current values beyond the limits may cause electric shocks, which
shall be tackled before returning the TV set to the costumer or connecting antenna or
accessories to it.
e. A high voltage limiting circuit (HVLC)is equipped with the TV set to control the high voltage
under the set value. Upon maintenance, do as specified in all the notes of the maintenance
manual, and the HVLC will function properly.
f. Maintenance warnings: At the largest contrast ratio, the high voltage of the TV set is lower than
31.0kV. In case parts affecting the high voltage are replaced, verify whether the high voltage of
the TV set is lower than 31.0kV at the largest contrast ratio. Use a voltage meter with a large
resistance and anti high voltage, to measure the high voltage. Connect the negative pole to the
grounding of the TV set core, and the positive pole to the high voltage connector. the connection
of the high voltage meter is shown in Fig. 2.
Note: Always turn off the powers of the TV set and the high voltage meter before connecting the positive
pole.
g. The X-rays (projection tube): The X-rays generated by the TV set are mainly from the
projection tube. Therefore the TV set takes use of the above said functions to reduce the
radiation hazard of the X-rays. In case the projection tube is replaced, only the same model or an
equivalent model certified by “CB” shall be used to ensure the protection function to the X-ray.
While troubleshooting or testing the TV set, avoid getting close to the projection tube and the
high voltage parts. Never run the TV set core for a very long time when troubleshooting the
causes of over high voltage.