HP Probook 470 G4 - Power and Charging Problem

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

BQACN/ACP continuity to CLR checked? ACDRV wont work untill CMSRC is 19V.

Hello, thank you. Are you able to explain where I would check this please? Looking up CLR shows Current Limiting Resistor, but I'm unsure how to identify this on the board? Looking at the board view, it shows BQACN connects directly to PR227, and there is continuity measured successfully between the two, and it shows BQACP connects directly to PR226, and again there is continuity between them.

[Sametbey]

Re: HP Probook 470 G4 - Power and Charging Problem

charge control chip voltages are attached, it will help, good works ,

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

charge control chip voltages are attached, it will help, good works ,

Thank you for posting that, that gives me a good idea of what I should be expecting.

I've been examining the board view and tracing back the BQACP and BQACN, and I can now see what I believe is the CLR, as both ACP and ACN connect back to PR237



I can see PR237 on my board just below the 2nd MOSFET here:



so I plugged my charger in and tested the voltage on either side of PR237 - 19.6v?? I was expecting to see 0v, based on my readings at the BQ chip ANC and ACP pins. So then I checked both the source and drain of BOTH MOSFETS PQ26 and PQ27 - 19.6v as well?! I then checked the gate of both MOSFETS and right enough, 25.74v!!

I couldn't understand this as I have done NOTHING since yesterday when I replaced the PQ26 MOSFET, which testing afterwards, had made no difference. I took a picture testing the gate voltage of PQ26



I'm glad I did. I then removed the power adapter and plugged in the fan, just to give a visual indication if i managed to turn the board on. After plugging the fan back in, and powering on the board, I am back to getting no voltage beyond the first MOSFET again. No more voltage on the PR237 and same readings as when I first started troubleshooting.

I removed the fan again, and tried the same tests, and still no voltage present. I've tried wiggling the DC IN connector while measuring voltage at the PR237 and cannot get it to happen again, however after leaving things for a minute, I did briefly get 19v back for a few seconds, but then it disappeared.

So other than being an intermittent issue, does the fact that I could get the correct voltages at these MOSFETS for a good few minutes actually confirm that certain components must be ok? Or am I left no further forwards and have to determine the intermittently failing component/s?

I never managed to get these readings before replacing the MOSFET, so whether that has improved things slightly I'm not sure.

[mon2]

Re: HP Probook 470 G4 - Power and Charging Problem

Flux and carefully remove the mosfet Q7. Power up again to test.

Be sure that your power adapter is the original and that the polarity of the power connector to the logic board is factory. Center pin will be positive.

HP power adapters use an analog voltage to detect the power rating of the adapter. If this reading is not suitable, the logic board can shut down. The EC usually monitors and makes this decision.

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

OK I will remove that mosfet and retest. Just to confirm, it's mosfet Q7 relating to the power button circuit here?



The dc in connector is genuine and original - I've owned the laptop from new and it hasn't been opened before. Also using the original HP charger - I've even just bought a new genuine HP charger from HP as a spare, which I'm currently using to test with. Centre pin is indeed positive.

[mon2]

Re: HP Probook 470 G4 - Power and Charging Problem

No. Q7 is the mosfet that is between the 2*DCin mosfets. See the earlier post #22 of the charger schematic.

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

Are you referring to the schematic that Sametbey posted in #22? If so, that must be from a different board model to mine, as I don't have a mosfet between the two DCin mosfets? The only reference to Q7 on my boardview is the one I mentioned relating to the power button, which is why I wanted to check if that's what you meant. Sorry if I'm missing something here. My power schematic is in post #23 which shows my board.

[mcplslg123]

Re: HP Probook 470 G4 - Power and Charging Problem

This is difficult to trace as board is working intermittently.Observe under microscope whether there is any corroded trace/element. Sometimes replacing the caps connected to dc-in fets gate helps in getting back the gate voltage. The replacement caps must be of same value and any random value replacement may make it worse.

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

Thanks, I'll need to invest in a microscope setup in order to progress and make things easier going forwards. I've been looking into various options recently so have an idea of what to look at for starting out.

The intermittent nature fits with the failure symptoms I was seeing prior to dismantling the laptop - where it would randomly just not turn on, the battery would deplete even with the charger plugged in, and some white charge port LED blinking occasionally, over the course of a couple of weeks, before finally just refusing to show any signs of life, at which point I dismantled and started to troubleshoot.

Strangely, this whole time of testing with my meter and taking various readings over the weeks, I have NEVER managed to see these correct voltage readings anywhere other than at the drain of the first MOSFET - yesterday was the first time, after seemingly nothing had changed. Although I'm enjoying the process, and extremely grateful to everyone that has assisted me so far, it's perhaps not the best board to start out on, having what seems to be some kind of intermittent issue - where the correct behaviour is witnessed very rarely...

In the meantime, I will carry on and remove the ~4k resistor which isolates the 2 DC IN mosfets from the ACDRV pin of the BQ chip and test the voltage on that pin - unless the most recent behaviour suggests it's no longer worth doing this? Can one of the 2 DC IN mosfets work/fail 'intermittently' in this fashion?

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

OK another update, with, what I think is good news.

Set up the meter again this morning, after changing nothing since yesterday. Plugged the charger in. Straight away, I'm getting the 19v power rail present on both mosfets, and around 25v on the gates!

The board hasn't moved position since testing yesterday. I kept the +ve meter probe on the PR237 leg as it's an easy test point to maintain, and gently started moving the DC IN port/cable around, like I was doing yesterday. After a few minutes of trying to move it in every possible rotation/flex position, i finally caught a voltage fluctuation on PR237. Honing in on the movement I was able to reproduce voltage drops down to around 5 or 6 volts and back up again.

I think after all this, it's looking like I may have finally found the culprit. Even though this was the first thing I checked, I obviously didn't manage to replicate the very specific position in which the voltage breaks - no doubt the areas that twists around the board around the hinge area, as they are quite tight turns.

I'm going to order a replacement DC IN adapter. I can't believe after all this - it's going to be down to something so simple. I'll obviously wait to replace and retest thoroughly before confirming - but I finally have some hope...

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

OK so new HP DC IN connector/jack arrived today, and fitted it straight away. Initially I thought great, I couldn't get the voltage to fluctuate/drop like I was getting with the old DC IN connector. Things seemed stable on the 19v power rail. I plugged the fan back in, and still getting the 19v power rail at PR237.

I plugged the power button back into the board so I could try power it up. The small white led on the power button board started flashing - in time with the clicking noise from the board, for 8 clicks/flashes, a second or so apart. Sometimes the white LED would stay on, and I seemed able to make it turn off from pressing the power button or holding it in. Nothing from the fan though, so nothing was trying to boot to bios.

I can maintain the 19v power rail for 30 minutes or so, but randomly I still lose it, WITHOUT MOVING ANYTHING - therefore I don't know if the old DC IN connector/jack was a bit of a red herring, or if it was one of multiple faults, however, the power rail is still temperamental, as is the clicking from the board.

I cannot seem to determine a pattern, and on one occasion something definitely tried booting to BIOS, as the board and heatsink started getting hot - typically i didn't have the fan plugged in otherwise I would have seen it before i felt it!

Will have to keep going trying to find a pattern, but it's proving taxing currently

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

Trying a different approach this morning. Removed the laptop charger and power button, and applied power at the charging port with my bench power supply - at the same entry point as the charger would provide the 19v so as not to introduce any voltage after any of the initial components on the board. There appears to be a minor fluctuation in amps, only 10mA comes and goes back to 0 every second or so, no change in the 19v. I'm not sure if this indicates that there isn't a short or not, but thought it might be worth ruling out any current draw.

I've then removed the power, and started checking the capacitors so see if any of them are short to ground, although I expect this would show by some amps being drawn continuously on my bench power supply? Please correct me if that's wrong but that's my understanding.

I straight away noticed that EACH of the first 3 capacitors that I checked gave a continuity beep to ground on BOTH sides. They are the ones around the area of my 2 DC IN mosfets, highlighted yellow here EC1023, EC51 and EC53:



I continued down the board, and each cap that I checked that relates to the 3v power rail was showing continuity to ground on both sides, however other caps such as the 3 at the very bottom of the above picture, which are GND one side and +VIN the other side, all measure correctly, so the issue does seem to point to the 3v rail. Am on on the right track here? If so, how do I find which component on the 3v power rail is causing the whole rail to short?

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

Resistance between any of the +3v caps and GND is 0.6 Ohms.

I forgot to mention that throughout this whole time, even with the new DC IN cable, I have not once had the LED on the DC IN Jack light up. Only the white LED on the power button yesterday. I believe the jack LED should light up amber when the battery is present and charging, but it should light up white to show the charger is present/providing voltage I believe.

[Sephir0th]

Re: HP Probook 470 G4 - Power and Charging Problem

Well, 3V_DEEP_SUS shorted to GND. This likely means it is a no fix, but let's check first. Inject 1V up to 3 Amps into this rail and see whether the PCH is getting warm/hot.

A short inspection of all inductors present on your board would have made it clear in seconds, but Well. Now it is too late anyway. So let's go into the final round...

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

Well, 3V_DEEP_SUS shorted to GND. This likely means it is a no fix, but let's check first. Inject 1V up to 3 Amps into this rail and see whether the PCH is getting warm/hot.

A short inspection of all inductors present on your board would have made it clear in seconds, but Well. Now it is too late anyway. So let's go into the final round...

Thanks. Before I started with the troubleshooting I did a visual inspection of the board for any signs of burn damage - using a loupe - and could not see anything at all. I did not however take any readings of any of the inductors - is this normally a good first step in these cases, or as a matter of course? If so, what readings should I have been looking for when checking the inductors?

I will do some test with the 1v injection on the +3V rail like you suggest and report back. In the meantime, I have noticed what looks like some sort of heat marking on top of one of the inductors - which, after checking my original photos of the board, wasn't there originally. So it seems this has come about at some stage through my testing, and I'm wondering if this is linked to the 3v rail issues I am seeing now perhaps. It's inductor PL37 (3R3727CL1), and it currently measures 1.5 Ohms to GND - see before and after pic's showing some sort of heat build up on top:



Just before I do the 1v injection testing, here are some more measurements, in case they help or suggest that the voltage injection may not be worthwhile for any reason:

Checking 3v rail

+3V_ALW = OK no short to ground
+3VPCU_VIN = OK no short to ground
+3V_RTC = SHORT TO GROUND
+3V_RTC_0 = OK no short to ground
+3V_RTC_1 = OK no short to ground
+3V_RTC_2 = OK no short to ground
+3V_SRC = SHORT TO GROUND

IC:

PU25
pin 8 51285_SW2 = SHORT TO GROUND
pin 10 51285_DH2 = SHORT TO GROUND
pin 11 51285_DL2 = OK no short to ground


INDUCTORS:

PL37 - 1.5 Ohms to GND
pin1 51285_SW2 SHORT TO GROUND
connects to mosfet PQ46 (Drain) which is a 7752 GA7S2D N CHANEL
This mosfet reads 0.004v between source and drain both ways, and 1.6 Ohms across
+source -gate = 0.637v / 2.3M Ohms
-source +gate = 1.098v / 6.5M Ohms

+drain -gate = 0.639v / 2.3M Ohms
-drain +gate = 1.113v / 6.5M Ohms

This mosfet reads between source and drain 0.487v and OL - seems OK 3M Ohms
Drain connects to +3VPCU_VIN - OK no short to ground

PL16 - 0.4 Ohms to GND
pin1 1237LX = SHORT TO GROUND

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

Just to clarify, as I didn't format my above post very clearly - results of testing the 2 mosfets near the inductor PL37:

Mosfet PQ46 is a 7752 GA7S2D N CHANNEL. The Drain of this mosfet connects to pin 1 of the PL37 inductor.

This mosfet reads 0.004v on diode mode between source and drain both ways (both polarities of test leads), and 1.6 Ohms across in resistance mode.
Also, on diode mode and resistance readings between gate pin and both the source and the drain (with lead polarities included):
+source -gate = 0.637v / 2.3M Ohms
-source +gate = 1.098v / 6.5M Ohms

+drain -gate = 0.639v / 2.3M Ohms
-drain +gate = 1.113v / 6.5M Ohms

So based on the Source -> Drain readings, it appears this mosfet is faulty?

Mosfet PQ44 is a B20N03 E0206 N CHANNEL. The Drain of this mosfet connects to +3VPCU_VIN.
On Diode mode and resistance mode, this mosfet reads:
+source -gate = 0.637v / 2.3M Ohms
-source +gate = 1.098v / 6.5M Ohms

This mosfet appears to show correct expected readings.

Is there any point at this stage removing/replacing the suspected faulty PQ46 mosfet? Could this be affecting the reading on PL37, or is that suspect faulty now also?

[Sephir0th]

Re: HP Probook 470 G4 - Power and Charging Problem

The "burned" Inductor is really near to the RT6575A, your 3V/5V Controller. So yes, if the Inductor has continuity with Pin8 then it is at least one of your shorted 3.3V rails. A shorted +3V_RTC in addition is already worse. And actually I don't understand from where the idea comes to still play with the Mosfets.
There are already many indications leading to a dead Platform Controller Hub. So just clarify the questions above, inject and see whether the PCH is getting hot to finally come to an end here.

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

The mosfet testing was simply because it was something else I thought I could check in the meantime, while looking at the shorted 3.3V rails.
This is my first ever board repair attempt, so I am learning as I go, with practically no experience in this field. Which is why I am probably checking things that are a waste of time at this stage, as it's all a learning experience.

Regarding the voltage injection - is there a 'best' place to inject the voltage on this rail, or can it literally be anywhere on the 3.3V rail as it doesn't make any difference?

[Sephir0th]

Re: HP Probook 470 G4 - Power and Charging Problem

The mosfet testing was simply because it was something else I thought I could check in the meantime, while looking at the shorted 3.3V rails.
This is my first ever board repair attempt, so I am learning as I go, with practically no experience in this field. Which is why I am probably checking things that are a waste of time at this stage, as it's all a learning experience.

Regarding the voltage injection - is there a 'best' place to inject the voltage on this rail, or can it literally be anywhere on the 3.3V rail as it doesn't make any difference?

Yeah, Chip-Level isn't kindergarden and it needs months till you reach a somehow acceptable success rate, also depending on how fast you learn and the sources you learn from.

Confirm, the Inductor is linked to the Controller as assumed, then you can inject into the inductor directly.

But don't expect miracles. A dead PCH/CPU/GPU are common outcomes with recent devices.

"Thanks. Before I started with the troubleshooting I did a visual inspection of the board for any signs of burn damage - using a loupe - and could not see anything at all. I did not however take any readings of any of the inductors - is this normally a good first step in these cases, or as a matter of course? If so, what readings should I have been looking for when checking the inductors?"

If you want to speed up your repair attempts then this is a great way to get a basic overview about the health of the whole board. Of course only, If you understand what to expect where.

[Scoff]

Re: HP Probook 470 G4 - Power and Charging Problem

Thanks for explaining. OK so I set the max current on my power supply to 3A, and set the voltage to 1v. Ground lead to board ground, and positive lead onto the inductor PL37.

I can hear a slight 'hissing' form my power supply, and the current draw shows as 840mA - nothing seems to get hot though, checking various inductors by feel, as well as the heatsink above where the PCH is.

Are you able to help explain what this result means please? I do have some 'freeze spray' as well as some IPA if it helps to check for a component getting warm, as I couldn't feel anything. Perhaps I need to keep the power injected for longer - I am currently holding it for around 10 seconds, as a bit unsure about the slight hissing noise from the power supply when doing so. Never heard that noise before, and don't get that when shorting the bench power supply pins together in order to set the max current initially.

Just to confirm, yes pin 8 does have continuity to that inductor.