HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

[Rbkfix]

Hello - this laptop originally as it had no power at all, battery was flat and wouldn't charge.

I traced the problem back to the connection to the screen, the positive supply for the LED backlight was shorted (not a direct but low resistance) to ground and was stopping the backlight from working and draining the battery quickly.

After taking these wires out of the connector, I connected them directly to a point on the PCB and then the backlight worked and the laptop booted up.

However an hour or so later something has happened to the laptop and now it won't boot up, I've checked my connections and nothing is shorted to anything, unsure if it is anything I have done or possibly a legacy fault caused by the original problem which has now surfaced.

What is happening is when the AC adapter is connected or the battery reconnected the laptop turns itself on automatically and the fan runs at full speed, the charge light then flashes orange 8 times, then lights up white and the orange LED flashes again 8 times. All LEDs light up on the keyboard solid without any flashing and then the laptop turns off. Several seconds later it turn back on again with the fan on full, keyboard LEDs on and then the charge light starts flashing orange and it tuns itself off again. The cycle continues to repeat.

I have measured the AC supply and it draws no more than 10 watts, so the battery is not charging and the processor is stone cold. There is no flicker or anything from the screen either.

Any advice would be greatly appreciated, and I don't have a schematic.

[app82]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

May be try to fix its bios battery. 10watts is hot, may be you can find something from it.

[Rbkfix]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

Thank you for your reply.

I've checked the BIOS battery and it is full at 3.08V, this is when connected to the board.

I don't think 10 watts is all that much, the power supply itself uses a few watts even when not connected and the fan at full consumes a few watts.

The only components which get slightly warm is an inductor next to the power jack and one near the battery area, this is after leaving the laptop for about half an hour just switching itself on and off.

Is there anything else I should check?

[Sephir0th]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

Probably you were dealing with a dying PCH, caused by the mentioned short, which you was able to revive, at least for a while.

However, the given informations are way to general to assume anything. We have to know on which signals/rails exactly you have worked before.

Additionally I agree that 10W are pretty much consumption, especially if the CPU is not supplied. But we don't know at this point, since you doesn't mentioned which voltages are present in the bootloop state and also whether the resistances are fine

[app82]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

Thank you for your reply.

I've checked the BIOS battery and it is full at 3.08V, this is when connected to the board.

I don't think 10 watts is all that much, the power supply itself uses a few watts even when not connected and the fan at full consumes a few watts.

The only components which get slightly warm is an inductor next to the power jack and one near the battery area, this is after leaving the laptop for about half an hour just switching itself on and off.

Is there anything else I should check?

the one near power jack is 12v bus supply and battery charger it should be ok. the other near the battery, you need to check it further for something shorted caps or it may doing overvoltage. if there is switching activity at mosfet side of inductor and no voltage at the output,
something is shorted. if the output present probably an overvoltage protection switch off the system.
edit: sorry I forgot it. if fan is spinning fast while the processor is off. probably something is wrong in pch or ec. warm inductor could be caused by the fan. but where did you connect the lcd cable?

[Rbkfix]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

Thank you for your questions/help so far

Sephir0th - I really hope the PCH wasn't dying, but could well be the case,I don't know the history of the laptop.

However the shorted pins were supplied by the 12V rail so I'm hoping the PCH is okay....

app82 - As you say the 12V bus looks okay and I have checked for shorts and I can find none, the battery area sees okay too, both inductors are conducting.

To help I've added a picture and written on the voltages I can find. The only voltages I have are 12, 5, 3.3, 1.2 and 1.02. The only difference when the mains AC is connected is the 12V bus jumps up to 13.3V.
There are no voltages present around the inductors above the processor.

The only work I have done is solder the black wires from the LVDS cable to a test point marked LED on the panel, I know this test point is connected to the 12V bus as I found continuity between where the black wires would connect to the connector and this test point and the backlight illuminated after making this connection.

[app82]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

To help I've added a picture and written on the voltages I can find.

1.2v is present but it is likely EC is missing powergood state from 1.2v or something similar to enable power to the cpu, and may need to be examined carefully. because no schematic available yet.

[Sephir0th]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

At least the whole CPU circuitry isn't up but there are even more coils in question. The lower right one I don't know the purpose and the most left 1.04V coil where I'm not sure it shows correct voltage. However, we could start with resistance to GND measurements of all coils without voltage

[Rbkfix]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

I'm going to try and find the EC chip on this board and hopefully a datasheet at least exists and I'll find the POWER OK signal

I've measured the resistances of the coils to ground and added them to the attachment. No shorts that I can see.

I also reapplied power and can confirm using a different multimeter the coils with 1.06V and 1.04V are still showing the same values.

[Sephir0th]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

Your 5VALW is partially shorted which points to a shorted controller or switch, or semiconductor in general.

First step is to lift the coil to confirm whether the short is located on buck converter or load side. If on load side, Inject 1V and look whether any component is at least getting warm. If not, you need to guess. Rule out each semiconductor on non powered rails and signals which should enable the rails, like load switches and so on.

Additionally I don't like the 16 Ohms of the 1.06V coil. Hopefully there is nothing already irreparable damaged.

Good luck.

[Rbkfix]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

Is the 5VALW the one at the bottom left coil? The one reading 5.18V?

I can lift the coil and inject 1V, but there is already 5.18V here when plugged in, this would cause the faulty component to heat up more anyway? Or should I be looking for 5V at another coil?

I'll keep probing and see if anything changes, many thanks

[Sephir0th]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

Yes, You could even look whether anything is significantly heating up without injecting. Sometimes you'll be lucky in these cases.

You need a basic idea what is supplied by this rail. Can be almost any controller present on your board, so concentrate on the first one without power, which seems to be the RAM supply. From location I'd say either the rail with 180 Ohms or 55 Ohms to GND. You can clarify by re-measuring Resistance without RAM module present. The coil who changes the value is the rail in question.

[kingjay]

Re: HP 840 G6 Laptop CRESCENT-6050A3022501-MB-A01(A1)

Yes, You could even look whether anything is significantly heating up without injecting. Sometimes you'll be lucky in these cases.

You need a basic idea what is supplied by this rail. Can be almost any controller present on your board, so concentrate on the first one without power, which seems to be the RAM supply. From location I'd say either the rail with 180 Ohms or 55 Ohms to GND. You can clarify by re-measuring Resistance without RAM module present. The coil who changes the value is the rail in question.

Has anyone found the solution to this? i also have the same problem. my started when updating the bios, the laptop whent off in the middle of the update. i have tried resetting the laptop and recover from bios using the USB stick but to no avail. Your help will be highly appreciated

[azhitko]

Hello - this laptop originally as it had no power at all, battery was flat and wouldn't charge.

I traced the problem back to the connection to the screen, the positive supply for the LED backlight was shorted (not a direct but low resistance) to ground and was stopping the backlight from working and draining the battery quickly.

After taking these wires out of the connector, I connected them directly to a point on the PCB and then the backlight worked and the laptop booted up.

However an hour or so later something has happened to the laptop and now it won't boot up, I've checked my connections and nothing is shorted to anything, unsure if it is anything I have done or possibly a legacy fault caused by the original problem which has now surfaced.

What is happening is when the AC adapter is connected or the battery reconnected the laptop turns itself on automatically and the fan runs at full speed, the charge light then flashes orange 8 times, then lights up white and the orange LED flashes again 8 times. All LEDs light up on the keyboard solid without any flashing and then the laptop turns off. Several seconds later it turn back on again with the fan on full, keyboard LEDs on and then the charge light starts flashing orange and it tuns itself off again. The cycle continues to repeat.

I have measured the AC supply and it draws no more than 10 watts, so the battery is not charging and the processor is stone cold. There is no flicker or anything from the screen either.

Any advice would be greatly appreciated, and I don't have a schematic.

I think it's worth updating the BIOS, for starters.
Most likely you will have to unsolder 2 BIOS memory chips. This is the simplest and very first thing to do.

[Nurshad]

Hp Elitebook 840 g6 6beep 3log beep 3short beep help me

[SMDFlea]

Hp Elitebook 840 g6 6beep 3log beep 3short beep help me

https://www.manualslib.com/manual/15...page=92#manual