Lenovo b450 LA 14 no power up 13mA

[maxsim86]

hi ..have a lenovo B450 no power Up. have 19v,3.3 v,5 volt but 5volt drop to 4.5v


L15 = 1.5 K Ohm
L6 = 34 K Ohm
L30 = 7.4 OHM
L7 = 18MOHM
L8 = 15.6OHM
L9 = 15.5OHM
L17 = 1.7KOHM
L16 = 18.6OHM

Schematic: https://www.badcaps.net/forum/showth...54#post1244154

[mon2]

Re: Lenovo b450 LA 14 no power up 13mA

Where are you measuring this 5v rail?

Measure the voltage to ground at U20 mosfet. Measure each pin of interest.

Source (1-2-3)
Gate (4)
Drain (5-6-7-8)

For any rail that is not matching the schematic value, remove all power, meter in resistance mode. Measure the resistance to ground to confirm there is no partially shorted part on the rail.

[maxsim86]

Re: Lenovo b450 LA 14 no power up 13mA

where are you measuring this 5v rail?

c258 = 4.5v


u20 resistance mode value :

pin 123 = 45kohm
pin 4 = 9kohm
pin 5678 = 4.6 M Ohm

[mon2]

Re: Lenovo b450 LA 14 no power up 13mA

From the linked schematic, c258 = M_VCCA_DPLLA

Is this correct? That is not a 5v rail but is 1D05V_S0.

[maxsim86]

Re: Lenovo b450 LA 14 no power up 13mA

From the linked schematic, c258 = M_VCCA_DPLLA

I am wrong C528, not c258...c528 is 51125_VBST2

[mon2]

Re: Lenovo b450 LA 14 no power up 13mA

Measure the voltage to ground at L6, pin #2. This is 5V_PWR.

Then also L15, pin #1. This is 3D3V_PWR.

Post each measurement.

[maxsim86]

Re: Lenovo b450 LA 14 no power up 13mA

L15 and L6 = 0volt

[mon2]

Re: Lenovo b450 LA 14 no power up 13mA

Measure the voltage to ground of DCBATOUT_51125 (pin 16) on this IC. This is the high dc voltage used as the input to this dual switching regulator.

For safety, it will be easier to measure the same power rail at U28 (pins 5-6-7-8).

[maxsim86]

Re: Lenovo b450 LA 14 no power up 13mA

found 19v at this point . here i list on ic u47:-

1) 1.4v
2) 0v
3) 2.0v
4) 2.0v
5) 0v
6) 1.3v
7) 0v
8) 3.3
9) 4.5
10) 0v
11) 0v
12) 4.9v
13) 1.48v
14) 3.3v
15) 0v
16) 19v
17) 4.9v
18) 0v
19) 0v
20) 0v
21) 0v
22) 4.5v
23) 0v
24) 0v

[mon2]

Re: Lenovo b450 LA 14 no power up 13mA

This regulator is remaining OFF due to ENTRIP1 & ENTRIP2 pins being logic low. Respectively, PGOOD is a logic low since both of these rails are not within specifications.

(netnames are 51125_ENTIP1 & 51125_ENTIP2)

L15 and L6 = 0volt

Remove all power -> meter in resistance mode -> measure the resistance to ground of L15 and then of L6.

Post each measurement.

reference - regulator datasheet:
https://cdn.badcaps-static.com/pdfs/...abc8077401.pdf

[maxsim86]

Re: Lenovo b450 LA 14 no power up 13mA

L6 = 1.27kOhm
L15 = 420 ohm

[mon2]

Re: Lenovo b450 LA 14 no power up 13mA

To me, these are both low resistance values for these power rails.

Do you have hot air tools? If yes, flux and hot air L15 to lift one leg. Then check the resistance to ground again on each side of L15 pcb pads. Be patient to apply enough heat and time to melt the solder.

Which side is with the low resistance? Is it the regulator (producer) side or the consumer (downstream) side?

[maxsim86]

Re: Lenovo b450 LA 14 no power up 13mA

yes i have, here a result of L15 1.41kohm and another side is 1.29kohm. if i put black probe at ground the result 1.69kohm and another side 2.0kohm

[mon2]

Re: Lenovo b450 LA 14 no power up 13mA

This is the same coil that was reporting 420 ohms earlier?

[maxsim86]

Re: Lenovo b450 LA 14 no power up 13mA

This is the same coil that was reporting 420 ohms earlier?

yes L15,or i am doing something wrong?