Some recent maintenance examples are now shared with everyone, for reference only, please ask the master to correct.
First, Lenovo V360 notebook computer, the fault does not start, there is no current on the power (current is less than 0.00A, my power is relatively garbage).
1. Check standby 3V\5V chip RT8223BGQW (screen printing DC=CB) 8th pin 3D3V_AUX_S5 normal 3.3V, 17th pin 5V_AUX_S5 normal 5V, 23rd pin POWER_GOOD no voltage, suspect RT8223 is bad.
2, check the information that some people said that TPS51123 can be replaced, no TPS51123 on hand, continue to check the data found that TPS51125\UP6182AG can replace TPS51123, use UP6182AG instead of RT8223, and then check PG signal is still not.
3. When the PG signal is measured, the power is automatically triggered, the current 0.6 is no longer rising, and the screen is not displayed.
4, online download EC BIOS brush into 25LD101 (128KB capacity), measured RT8223 23rd foot PG has 3.3V.
5, press the switch to trigger normally, the current rises all the way, the normal jump, the screen display, the maintenance is over.
Second, Lehua LED32C330 LCD TV, power-on standby bright red, boot black screen.
1. Test the motherboard boot pin PW_ON signal high level (standby low level), and keep it;
2. Measure the backlight turn-on signal BL_ON of the main board and keep it high. The 24V power supply of the constant current board is normal.
3, measuring the backlight constant current plate LED lighting voltage 25V, immediately after the boot to 50V or so, immediately dropped to 25V, no longer rising;
4. The resistance of the two ends of the lamp strip is several hundred K or more. It is suspected that the light bar is broken and the constant current plate is protected.
5, split screen check light bar, a total of 7 X18 lamp beads, each three groups, each group with a pointer multimeter RX1 file test found that a total of more than 20 lights;
6. Remove a good lamp bead from a 22-inch disassemble light bar (this process is completed with a return air furnace), all replaced bad, the test machine backlight is normally lit;
7, test the total voltage of the lamp about 63V, a single 9V or so, the end of maintenance.
Third, ASUS desktop board P8H61-M LX, failure phenomenon: no trigger.
1. Check the switch pin 3.3V high level, short to ground to become low level, do not trigger;
2, check I/O NCT6776F 61 pin is connected to the switch pin, the short switch will jump, indicating that the line is not broken;
3, check the 63rd foot of NCT6776F connected to the ATX power green line (boot line), 5V is normal, indicating that the middle is not broken;
4, short-circuit switch, 61 feet jump 0V, 63 feet voltage does not jump;
5, re-flashing BIOS is invalid, measuring I / O crystal 25MHz two feet have voltage (1V, 4V), check the waveform with an oscilloscope;
6, try to change the 25M crystal oscillator, power-on successfully triggered.
Fourth, Lenovo G465C laptop, fault: no trigger, standby current 0.23A.
1. Fully observe that the motherboard has lost 20+ capacitors (two repair machines), as if it was directly pulled out with pliers, I don’t know why;
2. The capacitor is energized and the fault remains unchanged. Hand touch the standby chip TPS51123 high temperature, replace it is invalid;
3, check the EC IT8502E 3.3V power supply pin to the ground short circuit, the material board to find a piece of IT8500E replaced, standby current dropped to 0.00A, does not trigger;
4. Rewrite the EC BIOS (two BIOSes of this machine), trigger normally, the current jumps normally, the external display is normally displayed, the internal screen is not displayed, and the screen is not bright;
5, check the LCD screen backlight power supply is normal, LVDS VCC no power supply, after the power supply MOS tube is turned on after the screen, the test machine appears after a day, and more and more serious;
6, brush the South Bridge BIOS, the boot is still a screen, the fault remains unchanged;
7, suspected that the screen line is abnormal, replace the screen line, the fault remains unchanged;
8. Measure the signal lines of each group of LVDS with an oscilloscope, and find that the amplitude of the waveforms of the 27th and 29th feet is too low, and the two signal lines are in phase waveforms (the other three groups are inverted waveforms);
9, from the LVDS interface all the way to the graphics card is not abnormal, after using the hot air gun to add the graphics card, the test machine does not boot;
10, after writing the EC BIOS, the boot does not light up, and the external connection has no signal;
11, with the hot air again plus welding graphics card (216-0809024) too high temperature directly leads to the core bursting tin;
12, re-purchase the new graphics card 216-0809024 (has planted tin), on the BGA rework station (first purchase use, three temperature zone, 4000 ocean, change the day to use the experience), do the graphics card boot normally bright screen;
13, the boot keyboard has been input "o" letter, press any key after normal, do not connect the keyboard, re-brush two BIOS, reinstall the system is still invalid (until now not resolved);
14. After booting into the system, I found no sound, and there was no sound in the external connection. The drive is normal, the speaker is good, there is no problem between the speaker socket and the sound card chip CX20671-11Z. The resistance between the 11th and 13th pins is 0, which should be the sound card damage;
15. Replace the sound card chip, start the sound normally, troubleshoot, and repair the whole machine.
Five, Lenovo G455 notebook computer, boot black screen is not obvious, the current is stable around 2.6-2.8A.
1, replace the memory, unplug, the current is unchanged, still not obvious.
2, disassemble, bare board boot current rises to 1.3A-1.4A, stable and does not jump, plus memory current is unchanged, AMD chipset, common disease is North Bridge virtual welding;
3, first use the hot air gun 330 to lightly blow the North Bridge for half a minute, cool and power up, the current jumps to around 1.8, the screen lights up.
4, remove the four corner sealant, on the BGA, up to 240 degrees plus welding North Bridge, boot normally. Master Lu reported that the temperature of each unit was normal and the machine was repaired.
Sixth, TCL L42E9FBE power board bare board repair, fault: no power, no standby voltage +3.3VSB. Board number: 40-IP42CS-PWJ1XG
1. Visually measure the U801 (DIP8 power chip) and blow it up. You can't see the model. The nearby R801 and R825 are burnt and you can't see the resistance value.
2, through multi-party query cases, drawings, etc., determine the power chip model is FSQ510, the burned resistance is 2R7;
3, because the FSQ510 is not stocked, the material plate has not been found, and finally found a Q0365R in the plasma Y board, the query data has the same function, the feet are different;
4, use FSQ0635R to change the pin position (do not move the peripheral circuit) instead of FSQ510, replace the burned resistor, power-on measurement standby +3.3VSB or no voltage;
5, measuring chip power supply 300V is only about 100V, remove the filter capacitor to see that one foot has rotted (is a common problem), after the replacement, +3.3VSB voltage is normal;
6. Short-circuit PW_ON to STB, measure the normal output of each group, and repair the board.
Seven, ASUS M4A77T SI desktop board boot 4 seconds power down, there are running code
1. Visually inspect the appearance of a triode PQ606 near the I/O for damage.
2. Measure the switch pin 5V normally. After triggering, it will become 1.2V and will not rise to 5V. When the diagnostic card runs to C7, it will not power down and the switch pin will return to 5V high level.
3, check the case, ASUS motherboard 822 exclusion has been criticized, the industry is well known, first start from the I / O. Online measurement of a no problem (no drawings, do not know the number), directly find a change, boot no longer lose power, the cat hit a dead mouse, the first one was caught by me;
4, the new problem comes out, after running the code to the DN, the machine does not light up, automatically reset and restart, after four or five times, the code can be run normally. The BIOS battery is 2.9V. After the new battery is replaced, the power is turned on once, no longer automatically reset. .
5, board repair.
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