Toshiba Satalite P850 power goes off after 3secs

[Mag107]

Hello guys n girls I have a Toshiba Satalite P850 Part No. PSPKBA-04000U and mother board is QEKAA LA-8391P Rev: 1.0.

Looking at this for a family member.
It was working and after working away for some time and when returned home the LT then didn't start up - so I'm told. What it does is when the power button is pushed the light on the power button and LED on the front both light for say 3sec and goes off. With the power supply on a LED comes on orange and turns the white after the battery is charged, nothing comes on the screen and no fan spinning or noises when the power button is pushed and lit for those 3secs and I have just removed the mother board so far..

It does have 19v + 5v and 3.3v and now with just the bare board and it's power supply it still does the same when I short the 1st 2 pins on the left of the power connector.

[Techtiger]

Re: Toshiba Satalite P850 power goes off after 3secs

Check the RTCVCC line Remove RTC Bat & RAM with no power to MB hold down the PWRBTW for 10 Sec put back everything & check , if no change in the Schematic test TPS51125 LDO 3/5 PL332 PL352 for +3VALWP +5VALWP, in this MB typical Prob in UCL1 IC check the in puts & outputs voila !

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

Check the RTCVCC line Remove RTC Bat & RAM with no power to MB hold down the PWRBTW for 10 Sec put back everything & check , if no change in the Schematic test TPS51125 LDO 3/5 PL332 PL352 for +3VALWP +5VALWP, in this MB typical Prob in UCL1 IC check the in puts & outputs voila !

Thank you very much for the reply

I will test that later this afternoon and get back with the results..

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

Hello again,

Check the RTCVCC line Remove RTC Bat & RAM with no power to MB hold down the PWRBTW for 10 Sec put back everything & check, I did this and there was no change..
TPS51125 LDO, I don't know what that is and if I'm testing PL332 + PL352 correctly there is 3V/5V. The UCL1 IC I can't find that sorry but this well could beyond me..

The only TPS I'm familiar with are found in Cars

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

Ok I now do know what a TPS51125 is and does but just need to find where it is on the board

The UCL1 IC I still don't know where and what that is yet..

Thanks.

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

Ok I now do know what a TPS51125 is and does but just need to find where it is on the board

The UCL1 IC I still don't know where and what that is yet..

Thanks.

If I want to order a replacment UCL1 IC what part number could I use?

[Techtiger]

Re: Toshiba Satalite P850 power goes off after 3secs

Hello again,

Check the RTCVCC line Remove RTC Bat & RAM with no power to MB hold down the PWRBTW for 10 Sec put back everything & check, I did this and there was no change..
TPS51125 LDO, I don't know what that is and if I'm testing PL332 + PL352 correctly there is 3V/5V. The UCL1 IC I can't find that sorry but this well could beyond me..

The only TPS I'm familiar with are found in Cars

TPS51125 voltage regulate if you get the out put of +3VALWP +5VALWP your IC is good LDO is low dropout pin 8 17 is LDO for PBTWN & SIO (page 44 SIO) ect
can you check KB9012QF-A3 (SIO) pin 125 67 114 110 voltagebe care full if pins are short during test set DEAD , for UCL1 uplode close PIC of the both side we will try to locate it

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

TPS51125 voltage regulate if you get the out put of +3VALWP +5VALWP your IC is good LDO is low dropout pin 8 17 is LDO for PBTWN & SIO (page 44 SIO) ect
can you check KB9012QF-A3 (SIO) pin 125 67 114 110 voltagebe care full if pins are short during test set DEAD , for UCL1 uplode close PIC of the both side we will try to locate it

Many thanks techtiger

I managed to find the UCL1 with the part No. 3271V 2N002MX1

I will look at the others..

SIO = Serial Input/Output

LDO = low-dropout regulator I'm learning

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

TPS51125 voltage regulate if you get the out put of +3VALWP +5VALWP your IC is good LDO is low dropout pin 8 17 is LDO for PBTWN & SIO (page 44 SIO) ect
can you check KB9012QF-A3 (SIO) pin 125 67 114 110 voltagebe care full if pins are short during test set DEAD , for UCL1 uplode close PIC of the both side we will try to locate it

Hello update time,

on the SIO pins 125 =3.37v pin 67=3.37v pin 114=3.37v pin 110=3.37v

Now is that good news or bad news?

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

Hello update time,

on the SIO pins 125 =3.37v pin 67=3.37v pin 114=3.37v pin 110=3.37v

Now is that good news or bad news?

I have purchased a new muiltimeter as mine was very old and the display was going and a hot air station to remove faulty componants.

Do I need them for this board or have I wasted my money?

[Techtiger]

Re: Toshiba Satalite P850 power goes off after 3secs

Hello update time,

on the SIO pins 125 =3.37v pin 67=3.37v pin 114=3.37v pin 110=3.37v

Now is that good news or bad news?

now test all this pin SIO 106 115 101 100 6 14 116 114 with out press PWRBTN & again with press PWRBTN voltage will drop to 0V & back to 3V

[Techtiger]

Re: Toshiba Satalite P850 power goes off after 3secs

I have purchased a new muiltimeter as mine was very old and the display was going and a hot air station to remove faulty componants.

Do I need them for this board or have I wasted my money?

if you want to learn muiltimeter & hot air station is compulsory but if its just to repair one motherboard wasted my money , page 47 is your DC to DC test Q29 Q30 all pins as you press the PWRBTN

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

now test all this pin SIO 106 115 101 100 6 14 116 114 with out press PWRBTN & again with press PWRBTN voltage will drop to 0V & back to 3V

Thank you very much for replying to me yet again

I will test that tomorrow and " page 47 " is your DC to DC test, where would I find that? sorry to trouble you..

[Techtiger]

Re: Toshiba Satalite P850 power goes off after 3secs

[QUOTE=Mag107;986598]Thank you very much for replying to me yet again

I will test that tomorrow and " page 47 " is your DC to DC test, where would I find that? sorry to trouble you..

[/https://www.badcaps.net/forum/showthread.php?t=46309&highlight=LA-8391P

2nd post #Schematic

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

[QUOTE=techtiger;986606]

Thank you very much for replying to me yet again

I will test that tomorrow and " page 47 " is your DC to DC test, where would I find that? sorry to trouble you..

[/https://www.badcaps.net/forum/showthread.php?t=46309&highlight=LA-8391P

2nd post #Schematic

Ah yes I found it page 47

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

if you want to learn muiltimeter & hot air station is compulsory but if its just to repair one motherboard wasted my money , page 47 is your DC to DC test Q29 Q30 all pins as you press the PWRBTN

Hello again and hope all is well.

So far Q30 has on the drain pins 5.1v and 3.7v on the source pins with no change if PWRBTN is pressed.

Q29 has 3.4v on the drain pins and 0v on the source pins with no change when the PWRBTN is pressed.

Going to look at the SIO pins 106 115 101 100 6 14 116 114 now..

[Techtiger]

Re: Toshiba Satalite P850 power goes off after 3secs

Hello again and hope all is well.

So far Q30 has on the drain pins 5.1v and 3.7v on the source pins with no change if PWRBTN is pressed.

Q29 has 3.4v on the drain pins and 0v on the source pins with no change when the PWRBTN is pressed.

Going to look at the SIO pins 106 115 101 100 6 14 116 114 now..

check again Q30 Source side with out gate voltage it cannot trigger or bad component what is the voltage on both Q29 Q30 Gate then press PWRBTN

[Mag107]

Re: Toshiba Satalite P850 power goes off after 3secs

check again Q30 Source side with out gate voltage it cannot trigger or bad component what is the voltage on both Q29 Q30 Gate then press PWRBTN

Hello many thanks for putting up with me

I will do that and report back my findings thank you.

Ok Q30 on the gate with PWRBTN pushed 0v

Q29 on the gate with PWRBTN pushed also 0v