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Lenovo y400 nm-a141 notebook maintenance without power on
Machine model: Lenovo y400 nm-a141
Fault phenomenon: the notebook does not power on
Maintenance process:
One Lenovo y400, nm-a141, can’t measure 3.3v5v in standby, pu4 main power supply 19, en and on signals, standby VL linear voltage is 5V, entrip1 and entrip2 are not measured, check the source of these two signals.
Lenovo y400 nm-a141 notebook maintenance without power on Figure 1.
Under the control of pq12, if the signal is changed to high level, pq12 2 pin 5 pin must be low level, 2 pin 5 pin is provided by VL to pull up VCC.
Lenovo y400 nm-a141 notebook maintenance without power on Figure 2.
Therefore, pq13 must be turned on. Pull down 2 pin 5 pin of pq12, mainpwon has signal, here there are two signals and a vs, which provide high level through a 100k resistor, but this signal is affected by mainpwon. If mainpwon is not available, vs will come to low level through pr57, and mainpwon must be repaired. The signal comes from temperature control chip PU2 through 0 ohm resistance pr51.
Lenovo y400 nm-a141 notebook maintenance without power on Figure 3.
Gt718tm’s 3 pin, 1 pin vcc5v is normal, 7 pin input is 4V, the third pin has no output. At the beginning of the forum, it is said that the thermistor Ph1 is out of order. Find this resistor.Boardview and Boardview are under control.
Lenovo y400 nm-a141 notebook maintenance without power on Figure 4.
This resistor is on the back of CPU, but there is no obvious fault Diode value is normal. It is suspected that the temperature control chip is broken, but there is no g718t in hand. I found another 8 pin chip on Parts motherboard, and compared the function of pin against the drawing, and installed the test No. 3 pin or no VCC.
If you want to get rid of pr23 without Current protection, the 3.3v5v will come out immediately. However, it is found that unstable can’t be started sometimes, but the reason can’t be found. Can it still be g718t? If you find the same chip written on the same chip from Parts motherboard, you can get 3.3V VCC by testing 3 pin, and the installation test is OK.
