THINKPAD T450S - NM-A301 no power

[Stunt]

Hi i've THINKPAD T450S - NM-A301 with no power when i diagnosed it i'm only getting 20v on the main power nothing else on U41 chip that generate 5v and 3v i only get 20v on VIN pin and 0v on EN, EN1 and EN2 pins when i check the schematic EN, EN1 and EN2 signals comes from SIO chip and there's no 3,3v around SIO chip there's only 20v on pin 65 that's. Is the SIO chip dead? please help

[Udemzy]

Re: THINKPAD T450S - NM-A301 no power

What do you have on pin 22,29,2?

You need the ic to generate vreg3 and vreg5 before talking about en1 and en2

[Stunt]

Re: THINKPAD T450S - NM-A301 no power

Hi on U41 Chip on Pin 2 = 0v. Pin 22 = 3.3v. Pin 29 = 0v

[Stunt]

Re: THINKPAD T450S - NM-A301 no power

What do you have on pin 22,29,2?

You need the ic to generate vreg3 and vreg5 before talking about en1 and en2

Hi on U41 Chip on Pin 2 = 0v. Pin 22 = 3.3v. Pin 29 = 0v

[Techtiger]

Re: THINKPAD T450S - NM-A301 no power

Hi i've THINKPAD T450S - NM-A301 with no power when i diagnosed it i'm only getting 20v on the main power nothing else on U41 chip that generate 5v and 3v i only get 20v on VIN pin and 0v on EN, EN1 and EN2 pins when i check the schematic EN, EN1 and EN2 signals comes from SIO chip and there's no 3,3v around SIO chip there's only 20v on pin 65 that's. Is the SIO chip dead? please help

What is the impedance on L4 /L3 coil ? Is the U41 getting hot when you touch ? Note down voltage on all pins of tps51220

[Stunt]

Re: THINKPAD T450S - NM-A301 no power

What is the impedance on L4 /L3 coil ? Is the U41 getting hot when you touch ? Note down voltage on all pins of tps51220

The impedance on L4 = 3.1 k ohms on L3 its not stable it keeps on jumping between Mili ohms and K ohms. The U41 is not getting hot. The Voltages on tps51220 pins there are all 0v except pin 22 which is 3.3v and pin 23 which is 20v

[mon2]

Re: THINKPAD T450S - NM-A301 no power

Remove all power. Meter in resistance mode (2k scale).

Measure the resistance to ground of VREG5 (pin 29) of U41.

Post the readings.

VREG5 will only enable if EN (U41, pin 12) is a logic HIGH.

EN (pin 12) of U41 receives this signal from the TQFP128 (Toshiba) part TB62D516FG (TQFP128 14X14) @ U101 (pin 96) = KBC ??

[Stunt]

Re: THINKPAD T450S - NM-A301 no power

Remove all power. Meter in resistance mode (2k scale).

Measure the resistance to ground of VREG5 (pin 29) of U41.

Post the readings.

VREG5 will only enable if EN (U41, pin 12) is a logic HIGH.

EN (pin 12) of U41 receives this signal from the TQFP128 (Toshiba) part TB62D516FG (TQFP128 14X14) @ U101 (pin 96) = KBC ??

VREG5 Pin 29 = 0.451 resistance to ground

[mon2]

Re: THINKPAD T450S - NM-A301 no power

VREG5 Pin 29 = 0.451 resistance to ground

This should not be the diode mode setting. Suggest the 2k ohm scale (or closest on your meter).

Can you confirm the resistance scale used for this measurement ?

[Stunt]

Re: THINKPAD T450S - NM-A301 no power

This should not be the diode mode setting. Suggest the 2k ohm scale (or closest on your meter).

Can you confirm the resistance scale used for this measurement ?

OK the resistance starts from 567.8 k omhs and keeps on droping rapidly until it reaches 457.6 k ohms that's when it becomes steady i don't understand it

[mon2]

Re: THINKPAD T450S - NM-A301 no power

The rather high resistance is ok and confirms there is no excessive load (ie. short circuit or a bad cap) on this rail. So this rail has no reason to turn OFF.

Now for this rail to enable, the EN pin of U41 needs to be a logic high as per the shared datasheet for this component.

This logic level for the EN pin comes upstream from the Toshiba component (pin 96).

Is the Toshiba component warm / hot to the touch ? Review if the power rails are present on this component.

[Stunt]

Re: THINKPAD T450S - NM-A301 no power

The rather high resistance is ok and confirms there is no excessive load (ie. short circuit or a bad cap) on this rail. So this rail has no reason to turn OFF.

Now for this rail to enable, the EN pin of U41 needs to be a logic high as per the shared datasheet for this component.

This logic level for the EN pin comes upstream from the Toshiba component (pin 96).

Is the Toshiba component warm / hot to the touch ? Review if the power rails are present on this component.

On pin 96 = 0v and resistance is 32k ohms. I get 20v on pins 99 and 65 only the rest of the pin are 0v. The toshiba component is not getting hot and there are no burnt signs on the chip