How to enter the service mode, adjustments, troubleshooting, schematic– Using ICs LA76812, LA78040, LA7841, LA7845, LC863232A
Color TVs
using LA76812/LA76814/LC863232A-5V57, AT24C04, TDA7056Q, LA78040/LA7841/LA7845,
PC817, BSC2433553-6P/BSC25-3355-8/BSC29-3801-13R LOTs
Excessive
high voltage can produce potentially hazardous X-ray radiation.
To avoid such hazards, the high voltage must not be above 31.0KV(14") or 35.0KV(21") under any conditions. The normal value of the high voltage of this television is 22.5KV(14") or 26.5KV(21") at max beam current (maximum brightness) under a 90-260V, 50/60HZ AC power source.
To avoid such hazards, the high voltage must not be above 31.0KV(14") or 35.0KV(21") under any conditions. The normal value of the high voltage of this television is 22.5KV(14") or 26.5KV(21") at max beam current (maximum brightness) under a 90-260V, 50/60HZ AC power source.
Service should not be
attempted by anyone unfamiliar with the necessary precautions on this
television. The followings are the necessary precautions to be observed before
servicing.
1). Since the chassis of this television is directly connected to the AC-power line (HOT chassis), an isolation transformer should be used during any dynamic service to avoid possible shock hazard.
2). Always discharged the picture tube anode to the CRT conductive coating before handing the picture tube. The tube is highly evacuated and, if broken, glass fragments will be violently expelled. Use shatterproof goggles and keep picture tube away from the body while handing.
3). When replacing a chassis in the cabinet, it always is certain that all the protective devices are put back in place, such as non-metallic control knobs, insulating covers, shields isolation resistor-capacitor network, etc
1). Since the chassis of this television is directly connected to the AC-power line (HOT chassis), an isolation transformer should be used during any dynamic service to avoid possible shock hazard.
2). Always discharged the picture tube anode to the CRT conductive coating before handing the picture tube. The tube is highly evacuated and, if broken, glass fragments will be violently expelled. Use shatterproof goggles and keep picture tube away from the body while handing.
3). When replacing a chassis in the cabinet, it always is certain that all the protective devices are put back in place, such as non-metallic control knobs, insulating covers, shields isolation resistor-capacitor network, etc
4).
Before returning the set to the customer, always perform an AC leakage current
check on the exposed metallic parts of the cabinet such as terminals, screws,
metal overlays control shafts, etc., to insure that the set is safe to operate
without danger of electrical shock.
Many
electrical 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, rated for higher voltage, wattage, etc. Replacement parts with special safety
characteristics must be replaced with the same number. The use of substitute replacement parts that do not have the same
safety characteristics as specified in the parts list may create shock, fire,
X-ray radiation of other hazards.
Automatic Degaussing
A degaussing coil is mounted around the picture tube, so that external degaussing
after mobbing the TV should be unnecessary. But the receiver must be properly
degaussed upon installation. The degaussing coil operates for about 1 second
after the power is switched ON. If the set is moved or turned in a different
direction, the power should be OFF for at least 15 minutes. If the chassis or
parts of the cabinet become magnetized, poor color purity will result. If this
happens, use an external degaussing coil. Slowly move the degaussing coil
around the faceplate of the picture tube, the sides and the front of it, slowly
withdraw the coil to a distance of about 6 feet before turning power OFF.
Method of access to the service mode
Using
the remote control performs the following steps:
1.
Press the RECALL key on the remote control and the volume key minus (V-) on the
TV at the same time. The service mode screen will appear on the screen of the TV the word
FACTORY, indicating that it is in mode of service.
2.
To enter the B / W mode (white balance) flies to press RECALL on the remote
control and volume less on the TV at Same time
3.
For color adjustments, vertical, press RECALL again the remote control and
volume less on the TV at the same time
4.
To return to the original TV position press the KEY RETURT on the remote
control and turn off the TV. ".
Line Mode
After
being in service mode, you can RGB bias, pressed "0" to decrease
"S-BRI"; pressing "1" to increase "S-BRI".
Pressing
"2" to decrease "R-BIA"; pressing "3" to increase
"R-BIA". Pressing "4" to decrease "G-BIA";
pressing
"5" to increase "G-BIA". Pressing "6" to decrease
"B-BIA"; press "7" to increase "B-BIA".
B / W Balance Adjusts
After
setting RGB bias to, press "Mute" to return to the mode
"B
/ W BALANCE", then press CH + or CH- to select the items in the "B /
W BALANCE" table, press VOL + or VOL- to select the items.
ADJUST
Mode (Preset related to tube used)
En
el modo "ADJUST", ud puede ajustar size, picture position, sub picture
status, OSD position, AGC status etc. , press CH+ or CH- to select items in the
" ADJUST " Table, press VOL+ or VOL- to adjust selected item.
SETUP Mode
In
the "SETUP" mode, you can select the options, AV / TV option, OSD
option, power ON / OFF option etc. , press CH + or CH to select the items in
the "SETUP" table, pressing VOL + or VOL- to select the settings.
Troubleshooting
No grating, no picture, no sound
General, these failures are produced by power sources, because of which refer
to a wider area, so that can be divided them two conditions to explain: no +B
110 V and existing +B 110V.
(1) No +B (110V) voltage (voltage of network AC 90~ 260V ) These failures may be caused by power supply switch.
(1) No +B (110V) voltage (voltage of network AC 90~ 260V ) These failures may be caused by power supply switch.
Existing +B 110 V
These failures may be caused by abnormal operation of horizontal scan, to confirm which can observe the filament of tube whether bright on.
If determined horizontal scan in abnormal operation, look for the failure start from the horizontal drive stage. Search upward to LA76812 with method of checking DC voltage and waveform according to sequence: PIN27/H.OUT port→ PIN25 power supply→VD622 output
These failures may be caused by abnormal operation of horizontal scan, to confirm which can observe the filament of tube whether bright on.
If determined horizontal scan in abnormal operation, look for the failure start from the horizontal drive stage. Search upward to LA76812 with method of checking DC voltage and waveform according to sequence: PIN27/H.OUT port→ PIN25 power supply→VD622 output
Existing grating and no picture
Because of the picture video signals and OSD characters display are input from PIN44, PIN15, PIN16, PIN17 of LA76812(N201), so to observe characters on screen of faulted TV can determine the approximate area of fault.
Because of the picture video signals and OSD characters display are input from PIN44, PIN15, PIN16, PIN17 of LA76812(N201), so to observe characters on screen of faulted TV can determine the approximate area of fault.
Existing grating, no picture and sound
Processing according Existing grating and no picture” at first, let the picture display normally, then check sound.
Processing according Existing grating and no picture” at first, let the picture display normally, then check sound.
CPU non-operating
This
chassis is consisted of main chip LA76812 controlled by Sanyo I2C bus and CPU
LC863232A.
LA76812 is a performance and quality IC including PIF, SIF, AFC, V/C/D, etc circuits.
TDA7056B used in BTSC sound system is a power amplifier.
CXA2104S is a BTSC decode function IC.
LA4225A used in MONO sound system is another power amplifier
LA78040 is used for vertical power amplifier
LA76812 is a performance and quality IC including PIF, SIF, AFC, V/C/D, etc circuits.
TDA7056B used in BTSC sound system is a power amplifier.
CXA2104S is a BTSC decode function IC.
LA4225A used in MONO sound system is another power amplifier
LA78040 is used for vertical power amplifier