HP Pavilion Laptop Motherboard Not Starting Up DA0R53MB6E1

[Zentech]

Ok, I have an HP Pavilion Motherboard that is not starting up. The model is DA0R53MB6E1 REV E R53. I got the schematic from HERE. I went through the startup voltage sequence. and I have detected the following.
-- CHARGER CIRCUIT --
19V ok at charger circuit.
pu8 is giving out ACPRES (which if I'm not mistaken is charger voltage connected)
PU8 ACDET I'm getting 2.7v

-- POWER SUPPLY 5VALW/3VALW --
PU7 has 19v VIN
REF 2V
HAVE 19V on drain of PQ50 and PQ53, but no 5V or 3V output
could it be the chip? I don't have oscilloscope to see the lgate/ugate pulse to mosfet, just voltmeter. looking for advise here.
any help appreciated
thanks

[mcplslg123]

Re: HP Pavilion Laptop Motherboard Not Starting Up

This is how you should check a 3/5V regulator:
01.Check VIN
02.VREG3 & VREG5
03.ENABLE
04.POWERGOOD
05.ENTRIP1
06.ENTRIP2

Measute these pins and report back.

[Zentech]

Re: HP Pavilion Laptop Motherboard Not Starting Up

This is how you should check a 3/5V regulator:
01.Check VIN
02.VREG3 & VREG5
03.ENABLE
04.POWERGOOD
05.ENTRIP1
06.ENTRIP2

Measure these pins and report back.

ok.. I just measure the voltages and this is what I found (power bt off)

VIN 19V
VRE5 5V
VRE3 3V
EN0 3.2V
POWERGOOD 0V
ENC 0V
ENTRIP1 0V
ENTRIP2 0V

I didn't know which of the two EN was enabled, I assume is EN0, but just in case I measure ENC too... I guess POWERGOOD goes the the KBC saying we're good to go... but is not there!
any help appreciated. Thanks

[mcplslg123]

Re: HP Pavilion Laptop Motherboard Not Starting Up

ENC-This is the Enable for this IC and this signal comes from kbc pin48 as S5_ON. Since this is missing, you need to check the basic requirement of kbc like Pin11/121/124/18/21/69/123/14/4

You can remove the resistor PR93 and inject 3V on IC side of this resistor to see if you get 3v/5V on coil.

[Zentech]

Re: HP Pavilion Laptop Motherboard Not Starting Up

ENC-This is the Enable for this IC and this signal comes from kbc pin48 as S5_ON. Since this is missing, you need to check the basic requirement of kbc like Pin11/121/124/18/21/69/123/14/4

You can remove the resistor PR93 and inject 3V on IC side of this resistor to see if you get 3v/5V on coil.

pin 11 VCC = 1.2 should be 3V Acording to schematic
pin 121 VPCU = 3.2V
pin 124 ECPWROK = 1.1V

this are my findings.. I didn't continue b/c I'm missing VCC which is only 1.2 and it should be 3V. Where does this 3V comes from? is this 3VALW? does the 3V/5V VPC needs ENC from kbc in order to provide 3/5V? if this is the case where does 3V on pin 11 (vcc) come from?

[mcplslg123]

Re: HP Pavilion Laptop Motherboard Not Starting Up

C451 and R406 are connected with this pin. Try removing them and see if 3V appears there. What is the resistance on Pin11?? Note the resistance before removing C451/R406 and re-check the resistance after removing these components.

[Zentech]

Re: HP Pavilion Laptop Motherboard Not Starting Up

C451 and R406 are connected with this pin. Try removing them and see if 3V appears there. What is the resistance on Pin11?? Note the resistance before removing C451/R406 and re-check the resistance after removing these components.

for some reason R406 is not in the motherboard, I think this went through some revision and they removed it or something because the number is there but the actual resistor is missing. I've noticed this with several other components.... where does this 3V come from? is it 3VPCU or 3V_S5? or internally from EC?

this are the measurement from EC
11 VCC = 1.2 should be 3V According to schmtic
121 VPCU = 3.2V
123 RSMRST = 0V
124 ECPWROK = 1.1V
21 ACIN = 3.1V
69 AD_AIR = 2.7V
18 LID_EC = 3.2V
14 WRST = 3.1V
4 EC_RCIN = 0.4V do I need this in order for the EC to come on?

I also have 3V on SW1 (power on) and as soon as I press btn voltage drops on pin 125, which is what it should do; however the board is not coming on. I don't the the S5_ON for the ENC power supply.

[mcplslg123]

Re: HP Pavilion Laptop Motherboard Not Starting Up

With VCC remaing low at 1.2V , there is no question of board getting on. Try removing the kbc, clean the pads and then apply power and see if you get 3v at pin11 of kbc. If you have the skills and eqipment, then give it a try or else go to a professional repair shop.

[Zentech]

Re: HP Pavilion Laptop Motherboard Not Starting Up

With VCC remaing low at 1.2V , there is no question of board getting on. Try removing the kbc, clean the pads and then apply power and see if you get 3v at pin11 of kbc. If you have the skills and eqipment, then give it a try or else go to a professional repair shop.

My question here's where does the 3V on VCC pin 11 come from? these are not 3V vreg from PU7, which is 3V,5V power supply. on the schematic it doesn't say where those 3V come from. Usually you see a page number. Once you press power btn, KBC sends signal to PU7 which is 3V,5VALW and enable those, and from there South Bridge gets engage. But where does 3V come from?
PS: the reason that I come here, like many other, is because we lack specialized knowledge, like in this case laptop motherboard. Even if you have knowledge of electronic repair, you still need to understand how a laptop motherboard powers up. No one knows everything from start. I'm sure at some point you didn't know either.
thanks for the help

[paulo66]

Re: HP Pavilion Laptop Motherboard Not Starting Up

There is a boardview file for this board.

https://drive.google.com/file/d/1v4P...UsNkK88Xa/view

This one in particular offers limited info so you still need the schematics for parts names and values. For instance, R406 is zero ohms, and it leads to 116 other components.

The KBC_P+3V must be derived from the +3.3v linear output of pu7. Which reads normal, right? One of those 116 parts must be sinking a bit of current.

What is the voltage across pin 8 of the bios chip?

Good luck.

[mcplslg123]

Re: HP Pavilion Laptop Motherboard Not Starting Up

@Zentech, If you are interested only on knowing wherefrom +3V on VCC of kbc comes from- then the answer is +3V LDO. You have LDO voltage but still voltage at VCC pin is low and that's where you need to focus on. You didnt follow what is suggested and keep on asking the same question again and again. Remove the kbc, clean the pads and check voltage at VCC pin. If it is stable 3V, your kbc is bad else you need to put it back.

[paulo66]

Re: HP Pavilion Laptop Motherboard Not Starting Up

Is it safe to power up the unit without the kbc in place? On another thread I was told not to do that.

Ldo is vreg, right? If there's 3.3 present at pin 8 of pu7, and there's less than 2v at kbc, then there is some kind of isolation. Otherwise the voltage loss would come all the way down to pu7.
The fact that there is a 0.3v difference under normal conditions seems to point to a semiconductor drop.

[mcplslg123]

Re: HP Pavilion Laptop Motherboard Not Starting Up

It is absolutely safe to power up without kbc. Yes LDO is vreg. I've explained and advised steps to solve the problem. If you are not convinced, you can explore more opinion from learned members of this forum or elsewhere. Thats your choice and i respect that.

[Zentech]

Re: HP Pavilion Laptop Motherboard Not Starting Up

There is a boardview file for this board.

https://drive.google.com/file/d/1v4P...UsNkK88Xa/view

This one in particular offers limited info so you still need the schematics for parts names and values. For instance, R406 is zero ohms, and it leads to 116 other components.

The KBC_P+3V must be derived from the +3.3v linear output of pu7. Which reads normal, right? One of those 116 parts must be sinking a bit of current.

What is the voltage across pin 8 of the bios chip?

Good luck.

pin 8 BIOS 3.3V
thanks

[Zentech]

Re: HP Pavilion Laptop Motherboard Not Starting Up

There is a boardview file for this board.

https://drive.google.com/file/d/1v4P...UsNkK88Xa/view

This one in particular offers limited info so you still need the schematics for parts names and values. For instance, R406 is zero ohms, and it leads to 116 other components.

The KBC_P+3V must be derived from the +3.3v linear output of pu7. Which reads normal, right? One of those 116 parts must be sinking a bit of current.

What is the voltage across pin 8 of the bios chip?

Good luck.

if one of these parts is sinking current/voltage and they're all connected to vreg pu7 3.3V why do I have 3.3V on 3VPCU ON KBC pin 121? if it is drawing voltage to ground and is all connected to same place? that's why I thought it was from a different place... I'm going to lift KBC to see if that makes any difference... thanks all for help

[paulo66]

Re: HP Pavilion Laptop Motherboard Not Starting Up

Second and third paragraphs in post #12. No answers yet, just speculating. Still trying to learn how the motherboards work at component level.

I´ve had a similar case with 1.8v ax pin 8 of the bios chip. Didn´t read the kbc vin because I didnt know what to look for. But the vreg was 3.3. The bios was defective.

[paulo66]

Re: HP Pavilion Laptop Motherboard Not Starting Up

It is absolutely safe to power up without kbc. Yes LDO is vreg. I've explained and advised steps to solve the problem. If you are not convinced, you can explore more opinion from learned members of this forum or elsewhere. Thats your choice and i respect that.

It´s not a matter of being convinced or not. It´s just me trying to learn with the limited info available. Instead of just, you know, blindly following orders.
I´m sure you know the old saying "Give a man a fish..." Maybe your knowledge is only empirical, and I respect that. Or maybe that´s your thing, in which case I´m out.

[paulo66]

Re: HP Pavilion Laptop Motherboard Not Starting Up

One thing I forgot to mention: maybe your laconic approach is the type professionals want to read. Practical advice for a quick fix. No time for theory because of deadlines. No customer likes to wait. I respect that and maybe this forum is not the right place for hobbyists that like to zoom in.

[paulo66]

Re: HP Pavilion Laptop Motherboard Not Starting Up

Last post in a row.

What about injecting 3.3 at r406 (opposite side of the kbc) or at the kbc itself (pin 11)?

[paulo66]

Re: HP Pavilion Laptop Motherboard Not Starting Up

Is there any continuity between kbc vdd and the +3v_rtc?

Because there is only one point in the schematic where it´s clear the connection between +3vpcu and +3v. Page 7. Locate D11 and D12. D11 prevents the coin cell current from reaching the ldo output of pu7, or the low resistance would drain the battery quickly. D12 on the other hand prevents pu7 from charging up the coin cell. Which isn't rechargeable.

They´re Schottkys. So all this is at the cost of D11 voltage drop of 0.3V. Hence +3V < 3.3V.
Diodes fail open. If there is a connection between +3V_RTC and the KBC Vdd, maybe D11 is faulty and the remaining voltage comes out of a dying cmos battery.