HP Elitebook 8470P Dead not Powering on drawing 0 amps.

[platinumsteel]

Hi guys hope you all are fine.I have a HP Elitebook 8470P have me confused.Hoping you guys can help me figure it out.It draws 0.00 amps and does not power on at all.I notice something weird on the 19V rail tho.I have 3v and 5v on coils tho.I have no PGOOD Signal on Pin 23 of the 3V/5V TPS51123RGER IC. I have Vreg3 which is 2.4V and Vreg5 Which is 5V. I have voltage on the TRIP1 and TRIP2 lines which I was told that it should not have any voltage there.Or else the IC goes into Protection Mode.Not sure if that is true.But anyway I have attached 2 pictures.One showing the voltages in relation to the schematic.Can you guys check it for me and see if you can pick up anything wrong? I started from the first at ADP_EN to the 2nd mosfet I believe.




And below I have attached a picture showing between Pin 4 of the mosfet and the resistor in yellow which in diode mode shows to be shorted. Please feel free to correct me if any mistakes. I am a newbie.I suspect that the Mosfet may be at fault.But am having a hard time finding an exact replacement for it.I might have to order that mosfet.But wanted to make sure that's actually the issue.Thanks

I have attached the schematic for this board below.Thanks

[qayyum786]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

Remove ''R6000'' and check impedance on both point to make sure which area has shorted
once got the low impedance point inject voltage to find the short

[SMDFlea]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

Pin 4 is not short,you have 5.9V there which is the correct voltage,as its connected between 2 resistors which is called a voltage divider

Vreg3 is too low.Do you have a DC power supply to inject voltage with

[platinumsteel]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

Pin 4 is not short,you have 5.9V there which is the correct voltage,as its connected between 2 resistors which is called a voltage divider

Vreg3 is too low.Do you have a DC power supply to inject voltage with

Thanks for pointing this out to me.Yes I do have a DC Power Supply to inject voltage. And also tools to remove components. Possible if you can tell me where to inject voltage and how much voltage and amps I can start to inject? Thanks.

Remove ''R6000'' and check impedance on both point to make sure which area has shorted
once got the low impedance point inject voltage to find the short

I would like to try this.But can you tell me how much I can inject if i do find the point with low impedance? I went ahead and removed R6000 and checked the 2 points and below i have posted the results.Hope i have measured correctly.

[SMDFlea]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

Vreg3 is the P3V3AL 3.3V always on voltage.Start by injecting 1V at 1 amp into that line,slowly increase the amperage,if it doesnt rise then slowly increase the voltage up to 3- 3.3V maximum ,if the amperage starts to rise check if any parts are hot to touch .

[platinumsteel]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

Vreg3 is the P3V3AL 3.3V always on voltage.Start by injecting 1V at 1 amp into that line,slowly increase the amperage,if it doesnt rise then slowly increase the voltage up to 3- 3.3V maximum ,if the amperage starts to rise check if any parts are hot to touch .

Hi smd I just finished injecting with a minimum of 1V and 1 amp to a max of 3V and 2.5 amps into that line and well i didn't get any amp draw or voltage drop.So it looks like it's time for me to give up i guess.

[SMDFlea]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

There`s only one enable pin for both vreg3 and 5, and the tonsel voltage is too low to issue power good.Don`t give up ,first try to resolder around the U6100 pins using plenty of flux and reflow if you have a hot air,if pin 8 is still only 2.4V after that replace the chip.

[mcplslg123]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

Give up-Why?? Its not that a difficult problem to solve. its either bad soldering on pins of tps51123 or the IC itself is bad. Vreg3 should be stable 3.3V. Entrip1 and entrip2 are enable for 3.3 and 5v-so you should get voltages there. I dont know where you heard this. ENTRIP=ENABLE(EN)+TRIP . The voltage on entrip lines should be like this roughly-eg if you have 130k resistor connected on entrip,voltage should be 1.3V approx. Without voltage on entrip pins ,you wont get voltage on coils of 3.3/5V

[platinumsteel]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

Okay thanks mcplslg123 for your input.I replaced the exact IC from a donor board and am not sure if the IC is 100% ok...But now I have 3.3 on Vreg3 .But as you rightly said no voltages on Entrip1 and Entrip2 and i have no voltages on the coils now. EN0 is present.Still no Pgood. And it's not drawing any amps still.I have 1 more donor board with an exact IC .I will try that one and see how it goes.If confusion I will have to order new chips on ebay and see how it goes.

[platinumsteel]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

I have a final question tho..The original IC for this HP Elitebook on schematic is a TI_TPS51123RGER_QFN_24P . And the replacement chip or donor IC i have used is a TPS51123RGER-GP .Is that a good match?

[SMDFlea]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

I have a final question tho..The original IC for this HP Elitebook on schematic is a TI_TPS51123RGER_QFN_24P . And the replacement chip or donor IC i have used is a TPS51123RGER-GP .Is that a good match?

Its the same. Before you try the new one can you measure R6198 pin 1,and U6104 pins 1,2 and 4 voltage before and after pressing the power button

[platinumsteel]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

Hi guys i just wanted to report back here and close this issue.Ended up in a kind of rabbit hole with this Model Board.Ended up getting the 19V rail and 3v/5v rail working by making a slight mod to the dc jack 3 pins so that it will detect the center Pin..then all voltages came up..Then powered it on and then it stayed at 0.27 amps ..no matter what we did it will always keep drawing 0.27 amps.Spent an entire day troubleshooting looking for issues and nothing.So apparently there is some kind of defect with this model board.When i look online for it on ebay.There are a ton of them selling as parts only.And the issue is ''will not Power on'' ..So i decided to not fight up with this board anymore.So thanks a lot to you all for the help and useful information as always.

[mcplslg123]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

We respect your decision but i still beleive the issue could be resolved with little bit more digging.

[Sametbey]

Re: HP Elitebook 8470P Dead not Powering on drawing 0 amps.

The general working principle is as follows, TPS51123 comes in 19v and outputs LDO 3.3v. It starts the KBC with LDO and comes with a 3.3v enable signal. TPS51123 sends the POWER_GOOD signal to KBC. It outputs 3.3v ALW and 5v ALW voltages. With the start command, other power units output 1.05v, 1.35v, 0.9v. the processor runs pch and RAM s. Step by step in as little as 0.5ms. When there is a problem, the current drawn can give an idea.