Lenovo g410 booting up displays logo on auto power off repair

Lenovo g410 booting up displays logo on auto power off repair

First look at the board number:

Lenovo g410 booting up displays logo on auto power off repair Figure 1.

Start one booting up on auto power off,switch again, each time a logo is displayed on auto power off.The first thing I think about is BIOS CPU and so on. Changing CPU is still the same phenomenon. Next, when you brush BIOS, it is still the same. If you don’t put in memory, you can see that it is switch to 2.3A. Thus,auto power off and booting up are auto power off.short-circuit BIOS 5 / 6 pin makes the motherboard unable to read BIOS, or does switch to 0.54a not auto power off,At this time, all Inductor and VCC are normal, and the plaorm reset is also normal. Since VCC is normal, it is suspected that there is a BIOS problem. If the BBS finds a reliable BIOS and brushes it again and again, it is still the same to change a BIOS chip to continue to brush.The third board axe is finished. It seems that we can check it carefully.It is worth noting here that auto power off does not drop to zero directly after booting up, but drops to 0.2A after switch to 2.3A,Then it drops to 0 after a few seconds. When it drops to 0.2,VCC, such as memory, bus, CPU, graphics card, etc., are normal. It is found that there is only one Inductor without VCC.After the power is cut off, there are hundreds of normal values to the ground, and the output of pu601 is controlled by susp.

Lenovo g410 booting up displays logo on auto power off repair Figure 2.

Lenovo g410 booting up displays logo on auto power off repair Figure 3.

The measurement found that the 1.5V VCC at the moment from switch to booting up is normal, and the chip is extremely hot when the current goes up. When the current drops to 0.2A, the VCC will be gone, and other VCC will still be there.At this time, the measurement of its main VCC is also normal, no output?The chip should be broken.It may be that after switch runs out of code, the current required is relatively large, and the chip can’t carry it,Replace the chip results are still the same, oscilloscope grasp Inductor before and after the waveform is normal.

Lenovo g410 booting up displays logo on auto power off repair Figure 4.

The chip instantaneously high temperature, then changed the boost Capacitor, changed Inductor, found that pin was broken.

Lenovo g410 booting up displays logo on auto power off repair Figure 5.

The result is still the problem of auto power off and PCB layer?Think of the grafting, is the 1.5V conversion out of the secondary VCC Short circuit, along the drawing all the way down.Most of the 1.5V are directly into the bridge. When testing Inductor Diode value is normal, the key is to check the place where the VCC is converted. All the way to uv4, it is converted to the graphics card VCC.Find this convert transistor on the motherboard,An anomaly was found in the test.

Lenovo g410 booting up displays logo on auto power off repair Figure 6.

Lenovo g410 booting up displays logo on auto power off repair Figure 7.

The second level VCC has been completely Short circuit, this is for the graphics card VCC,booting up dropped, took a lot of detours to find the root.Remove the uv4 and start the machine, no longer auto power off, directly remove the field tube of uv4 without installation, and enter the system test, no problem, and repair the fault.