samsung R428 no power

[rickybucalan]

hello every one. i just wanna ask for help. i got samsung r428
model: suzhou-UL-DDR3
BA41-01214A

Can't power on.

checked : 19v line is ok

there is no 5v & 3.3v on coil

and i notice TPS51125 for 5v & 3.3v supply is getting hot.

i already tried to replaced it but no luck it was same

could anyone help me to find out what was the problem.

thanks.

tps 51125 checked Pin output voltage

pin 16 VIN 19V
Pin 13 ENO 4.8v
pin 17 VREG5 3.9v
pin 3 VREF 2v

[RethoricalCheese]

Re: samsung R428 no power

Check for short on +3.3V ALW.

[rickybucalan]

Re: samsung R428 no power

check for short on +3.3v alw.

there is no short at 3.3v line

[mielta]

Re: samsung R428 no power

Hi
Check Pin8 Vreg3

[mielta]

Re: samsung R428 no power

this goes to KBC Controller U516 Pin14,39 and some other
check for short

[rickybucalan]

Re: samsung R428 no power

hi
check pin8 vreg3

pin 8 2.2v

[rickybucalan]

Re: samsung R428 no power

this goes to kbc controller u516 pin14,39 and some other
check for short

there is no short in

pin 14 , 39, 40 ,119, 106, 84, 58, 68, 49.

[rickybucalan]

Re: samsung R428 no power

and i noticed tps51125 chip gets hot. i dont know what was wrong

[caspian]

Re: samsung R428 no power

here is the schematics:
https://www.badcaps.net/forum/attach...5&d=1500837159

how much resistance is at Pin8 and Pin17 and L6 and L7 relative to ground? the value of resistance is important.

[rickybucalan]

Re: samsung R428 no power

here is the schematics:
https://www.badcaps.net/forum/attach...5&d=1500837159

how much resistance is at Pin8 and Pin17 and L6 and L7 relative to ground? the value of resistance is important.

i got

04.15k ohm pin 8
083.0k ohm pin17
1.880k ohm L6
15.70k ohm L7

[caspian]

Re: samsung R428 no power

how much voltage is at pin1 and pin6 of tps51125?

[rickybucalan]

Re: samsung R428 no power

how much voltage is at pin1 and pin6 of tps51125?

no voltage at pin 1 and 6

[caspian]

Re: samsung R428 no power

considering all the symptoms, it seems tps51125 is faulty itself. but I am not sure. if tps51125 is available from scrap boards, replace it again.

[rickybucalan]

Re: samsung R428 no power

considering all the symptoms, it seems tps51125 is faulty itself. but I am not sure. if tps51125 is available from scrap boards, replace it again.

i just did but it still same.

[piernov]

Re: samsung R428 no power

Voltage and resistance to ground on PRTC_BAT?

[NIKHILKYOHANNAN]

Re: samsung R428 no power

check the impedance of smd capacitors around ICH(U517) and SIO(U516).

Once i got the same problem,that time my SIO was faulty. Replaced SIO. it got ready.

[mcplslg123]

Re: samsung R428 no power

I'll suggest to remove kbc, clean the pads on mb and connect ac adapter and check tps51125 is getting hot or not.

[dj_ricoh]

Re: samsung R428 no power

If that tps gets hot then there is something shorted to ground.

If kbc it's shorted then you can't power if you lift it right?
There need to be an output that tps it's giving that is shorted.