Samsung NC110 - Does not turn on.

[bpjl]

Hello.

I have a motherboard (Lennon BA92-07684B) from the Samsung NC110. The motherboard does not turn on.



When the power is supplied, the green LED lights up, but the board does not draw any power. When you try to turn it on there is no reaction. Sometimes, however, the blue LED will blink and 120mA will be consumed. Then the TPS51125 chip (visible in the picture below) starts to heat up.



When I connect the battery to the motherboard and connect the power supply, the difference is that the green LED turns red, which indicates charging and when the board has already responded to the button, the current consumption jumps between 180 and 230mA.

I am asking you for help in solving the problem.

[piernov]

Re: Samsung NC110 - Does not turn on.

TPS51125 should not heat up. Measure resistance to ground on VREG3 and VREG5 pins.

[bpjl]

Re: Samsung NC110 - Does not turn on.

Thank you for the quick reply. Here are the results of these measurements:

• VREG3 = over 20MΩ (limit of my multimeter)
• VREG5 = over 20MΩ (limit of my multimeter)

[bpjl]

Re: Samsung NC110 - Does not turn on.

Yesterday I got the same MOB With similar issue no power at all it was the first MOSFET was not driving 19V to the Mob now it's working
Mesures voltage
Page 37 Schmatic
U521 ic
Pin 3.8.16.17 voltage
L8 coil
L9 coil
Page 38
Bat connect
Pin 6.7 voltage
Page 14 RTC
D523 pin 1.3 voltage (3.3V MICOM)
Page 36
Coil L7 voltage
U3 ic
Pin 1.6 voltage
This is your S5 state
And the rest of the gray coils multimeter diode mode red probe to GND black to coil For resistance
Report back

The first MOSFET AO4807 works rather well for me:

• D1 = 19V
• D2 = 19V
• S1 = 19V
• S2 = 19V
• G1 = 9.4V
• G2 = 2.3V

I do not have a schematic so I do not know which elements it is (especially that they are not described on the PCB)

I suspect that "U521 ic" is a heating TPS51125. Here are the measurement results:

• pin 3 = 2V
• pin 8 = 3.3V
• pin 16 = 18.9V
• pin 17 = 4.9V

Power button voltage?

[Techtiger]

Re: Samsung NC110 - Does not turn on.

try this Schmatic

[bpjl]

Re: Samsung NC110 - Does not turn on.

Page 37 Schmatic
L8 coil
L9 coil

Page 38
Bat connect
Pin 6.7 voltage

• pin 6 = 0.4V
• pin 7 = 0.4V

Page 14 RTC
D523 pin 1.3 voltage (3.3V MICOM)

There's no D523 on this schematic. On page 14 is D513 (BAT54C) and if it is this diode then:

• pin 1 = 3.3V
• pin 3 = 3.1V

Page 36
Coil L7 voltage
U3 ic
Pin 1.6 voltage

• L7 = look @ picture above
  
• U3 - can't find it on PCB

[Techtiger]

Re: Samsung NC110 - Does not turn on.

TPS 51125
PIN 1.6.13.23 Voltage
if TPS 51125 getting hot considering all the symptoms, it seems tps51125 is faulty itself. but I am not sure. you have to test caps & resreters near

Bios Pin 8 Voltage

KBC VCC pin14 Voltage
In addition to TPS 51125 KBC might me be faulty if it's not sending ENTRIP1 and ENTRIP2
may be some one else can take from this point

[bpjl]

Re: Samsung NC110 - Does not turn on.

TPS 51125:

• pin 1 = 1V
• pin 6 = 1.4V
• pin 13 = 1.2V
• pin 23 = 0V

Bios Pin 8 Voltage

• pin 8 = 3.2V

KBC

• pin 14 = 3.2V

[Techtiger]

Re: Samsung NC110 - Does not turn on.

TPS 51125:
pin 23 = 0V on the pin23 of tps51125 you must be +3v that is your 3v/5v power good signal correct if i wrong some one else do you get 3.3V in power button ? try to flash bios with a working on or change TPS51125

[bpjl]

Re: Samsung NC110 - Does not turn on.

For lack of time, I put off work with this netbook for later. Then suddenly came the opportunity to buy exactly the same computer, with a broken screen, for little money.

Further solution to the problem was simple

Thank you all for your help and best regards.