HP - LA-D704P Rev 1.0 No Power Motherboard HELP

[mon2]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

It is important to note again that the mosfets attached to pu301 are dual mosfets inside the single package.

Post your measurements and the pins used for each resistance check.

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

It is important to note again that the mosfets attached to pu301 are dual mosfets inside the single package.

Post your measurements and the pins used for each resistance check.

I will share the measurements soon.

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

It is important to note again that the mosfets attached to pu301 are dual mosfets inside the single package.

Post your measurements and the pins used for each resistance check.

PQ301(Mosfet removed. values taken from the pad)

Source(5,6,7) to drain(2,3,4) -----> 6.38kohms
Source(5,6,7) to Gate1(1)-----> No value
Source(5,6,7) to Gate2(8)------> No Value
drain(2,3,4) to Gate1(1)-----> No value
drain(2,3,4) to Gate2(8)------> No Value
D2/S1(pin9) to ground-----> 0.4ohms (this is the short I guess)

PQ302(Mosfet is on the board)

Source(5,6,7) to drain(2,3,4) -----> 6.36kohms
Source(5,6,7) to Gate1(1)-----> No value
Source(5,6,7) to Gate2(8)------> No Value
drain(2,3,4) to Gate1(1)-----> No value
drain(2,3,4) to Gate2(8)------> No Value
D2/S1(pin9) to ground-----> 8.07kohms

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

🙄

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Any luck

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

waiting for a reply

[mon2]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Putting out our own local fires so immediate replies are not always possible. Have an ipad from h*ll that almost burnt the owner's hands - good job Apple / Foxconn. Wage bonus for the design engineers. Just purchased the over priced thermal camera from Qianli which is not really helping. Any metal object is showing a higher temp than the parts. My hands are on 'fire' from the thermal view. Perhaps a learning curve here...

D2/S1(pin9) to ground-----> 0.4ohms

Not good. So the short is either INSIDE the power supply IC @ PU301 if it is still soldered onboard OR could be downstream since the inductor PL302 is onboard.

Start with lifting one leg of PL302 coil / inductor. Once this leg is removed, check the same pin # 9 of the dual mosfet resistance to ground.

If the short is gone, then the short is INSIDE the power supply IC PU301.

Post your test results.

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Ops. sorry to hear about that.


actually PU301 already desoldered. still short on the pads.

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Not only the PU301. the power supply also removed from the board. So we can make sure the short isn't because of the power supply

[mon2]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Do you see a solder blob @PJ330 ? As a quick test, lift up one leg of PC309 capacitor.

Check if the short is still there. This power rail feeds all over the board but check this cap first.

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Do you see a solder blob @PJ330 ? As a quick test, lift up one leg of PC309 capacitor.

Check if the short is still there. This power rail feeds all over the board but check this cap first.

It's really hard to find components because the schematics part numbers are different from the what I see on the PCB.

Already removed that Capacitor but still short present.

[mon2]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

With care, inject 1v onto this shorted line and check to see which part heats up.

Again, we want to keep the voltage low so that it does not kill the CPU, in case this rail reaches the CPU due to a leaking mosfet. It is possible the CPU is the fault but you will know from the heating up of the component.

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

With care, inject 1v onto this shorted line and check to see which part heats up.

Again, we want to keep the voltage low so that it does not kill the CPU, in case this rail reaches the CPU due to a leaking mosfet. It is possible the CPU is the fault but you will know from the heating up of the component.

Already Injected 0.8v @ up to 5A and no one was heated. you can see that on our past messages. I removed the heat sink to test cpu as well. nothing found with my finger tips.

unfortunately I don't have a thermal camera to see a better view.

Do I need to inject again or whats next?

[mon2]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

We just purchased a $1k thermal camera - so far not impressed with the results. The only thing heating up is my body heat and fingers as they traverse under the camera.

Trying to locate a part that may be causing the ipad to stall @ 467mA - others are reporting this fault as well. Some videos claim a bad cap but so far unable to find one.

Remove all power. What is the resistance to ground of your CPU Vcore rail ?

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Remove all power. What is the resistance to ground of your CPU Vcore rail ?

I see 4 Inductors.

1---> 18.2ohms
2----> 17.6ohms
3----> 32.7ohms
4-----> 0.4 ohms

See the attachment.

[mon2]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

When you inject the voltage at the earlier 3v3 site, do you see any voltage at the coil with the 0.4 ohms ?

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

When you inject the voltage at the earlier 3v3 site, do you see any voltage at the coil with the 0.4 ohms ?

1v with 2.4A injected again.

No voltage at any of those 4 coils.

[mon2]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Yet, someone is consuming this current when you inject the voltage. The part is just not warm or hot enough for you to sense the location. Perhaps the part is on the bottom side?

At your discretion, this is risky, but you can consider to dial up the voltage to a higher voltage but must remain under the expected 3v3 (max). Suggest, perhaps 1v5. Test again with the injection. The risk is if some mosfet is leaking and hits a low voltage rail at which point this higher voltage will kill that part.

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Injected upto 2.7V at max 5A. I'm afraid to go more. however nothing heats up. How is that possible. I checked both sides of my board. nothing heats up.

However after 2-3 minutes My DC power supply fan gets on. I guess he is the person who heat by seeing this.

What can we do?

[harshana]

Re: HP - LA-D704P Rev 1.0 No Power Motherboard HELP

Still I have no Idea whats wrong with this. can't we disconnect sections one by one from 3v and test. worst thing is, there is no actual Schematics and also boardview file