Lenovo T460 board no: NM-A581 rev. 2.0

[Zilicon]

Please, I need your assistance on the above motherboard.

The board powers on and dies in less than two seconds. no display on the screen. fan stops immediately the power led light goes off. No beep when RAM was removed.
I have reset the CMOS, but nothing still.

However, I noticed that when the board is turned on, there was a strange noise coming from the CPU area- a kind of light-deafening sound but stopped when the laptop dies.

Please help, I don't know the next line to take.

thank you

[mon2]

Re: Lenovo T460 board no: NM-A581 rev. 2.0

1) Post the voltage readings for the attached locations.

2) Power down, meter in resistance mode (200 ohms). Red lead on location 4, black to ground. What is the reading in ohms ?

At this time, interested to review the resistance to ground to check for possible capacitor shorts which will be with low resistance values.

If the resistance reading is not too low, consider to repeat the resistance check on each grey coil on your logic board. Each coil is linked to a local switching power supply rail. Often polarized caps are on such rails and they do fail over time. Post your values and locations.

The noise you are probably hearing is the audible range of the local switching power supply rail for the CPU. Switching power supplies turn ON & OFF the voltage rapidly. In general, they are not in the audible range for humans but could be due to a shorted cap, etc. A shorted cap will present a low resistance to ground = heavy load to the power rail and the power supply IC will sense this heavy load by the reading of the current sense resistor and then perform a quick shut off to prevent any damage.

[Zilicon]

Re: Lenovo T460 board no: NM-A581 rev. 2.0

1) Post the voltage readings for the attached locations.

2) Power down, meter in resistance mode (200 ohms). Red lead on location 4, black to ground. What is the reading in ohms ?

At this time, interested to review the resistance to ground to check for possible capacitor shorts which will be with low resistance values.

If the resistance reading is not too low, consider to repeat the resistance check on each grey coil on your logic board. Each coil is linked to a local switching power supply rail. Often polarized caps are on such rails and they do fail over time. Post your values and locations.

The noise you are probably hearing is the audible range of the local switching power supply rail for the CPU. Switching power supplies turn ON & OFF the voltage rapidly. In general, they are not in the audible range for humans but could be due to a shorted cap, etc. A shorted cap will present a low resistance to ground = heavy load to the power rail and the power supply IC will sense this heavy load by the reading of the current sense resistor and then perform a quick shut off to prevent any damage.

Thank you so much for responding.

Below are the readings taken as directed:

1- 20V
2- 20V
3- 19.6V
4- 19.6V

Resistances:

4- no reading bit it reads 1.1M when I adjusted the meter to 200M

On coils

PL301- no reading
PL101- no reading
PL201- no reading
PL202- no reading
PL404- 12.7ohms
PL401- 7.0ohms
PL402- 6.6ohms
PL702- 65ohms

Note: my multimeter reads 2.0ohms for ground to ground