ASUS X550CL - Works only with battery ?

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

Power is nothing without control. What are the gate voltages,where do they come from ?

I think , that i have replied to anything that matters on the mosfets ? (both of them) .
Power (19V) doesn't go from MOSFET 1 to MOSFET 2. But the line between the 2 is clean and connected.
Now,the 19V come to the first MOSFET but "never" leave this MOSFET ( even with the replacements ).
So the 2nd MOSFET , to the pins that SHOULD Have 19V doesn't have any Voltage.

[SMDFlea]

Re: ASUS X550CL - Works only with battery ?

I think , that i have replied to anything that matters on the mosfets ? (both of them) .
Power (19V) doesn't go from MOSFET 1 to MOSFET 2. But the line between the 2 is clean and connected.
Now,the 19V come to the first MOSFET but "never" leave this MOSFET ( even with the replacements ).
So the 2nd MOSFET , to the pins that SHOULD Have 19V doesn't have any Voltage.

Pin 4 of the mosfet is the gate,the voltage has to 25V .Measure it,where does this gate voltage come from,what generates it

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

Pin 4 of the mosfet is the gate,the voltage has to 25V .Measure it,where does this gate voltage come from,what generates it

As i said , above. There is NO other, voltage shown in the meter.

Mosfet one , 19V comes in (single pad).
Never leaves the "mosfet"

Mosfet two , nothing comes on it.

If you see above the pictures are shown what is coming ,and nothing is "going"...

Even with different mosfet.

[SMDFlea]

Re: ASUS X550CL - Works only with battery ?

As i said , above. There is NO other, voltage shown in the meter.

Mosfet one , 19V comes in (single pad).
Never leaves the "mosfet"

Mosfet two , nothing comes on it.

If you see above the pictures are shown what is coming ,and nothing is "going"...

Even with different mosfet.

Measure the voltage on PR8809, both sides.Then with no power test the resistance ,it should measure 4.02K Ohms

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

Measure the voltage on PR8809, both sides.Then with no power test the resistance ,it should measure 4.02K Ohms

0 voltage on both sides.


4.11K Ohms resistance.

[SMDFlea]

Re: ASUS X550CL - Works only with battery ?

0 voltage on both sides.


4.11K Ohms resistance.

Pin 2 connects to PU8802 ,pin 4 .Read the description for pin 4 in the datasheet and tell me what voltage you expect to see on PR8809

https://www.ti.com/lit/gpn/bq24725a

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

Pin 2 connects to PU8802 ,pin 4 .Read the description for pin 4 in the datasheet and tell me what voltage you expect to see on PR8809

https://www.ti.com/lit/gpn/bq24725a

Good morning SMD!

Just checked it.
Only (Pin 1 has 19volt) all the other are "dead" .

( I have the old - factory mosfets which used to work with battery only , just in case i need to explain myself :P )

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

Suddenly the laptop was alive.
It posted windows, it still holds charge (2 hours left on battery).

But again , doesn't detect the DC-Jack charger ...
(It doesn't charge the battery ,even though it shows that "19volt are coming in the dc-in)

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

So maybe the "CHARGE MANAGE IC BQ24725ARGRR
TI QFN-20" is the problem ? That doesn't detect the charger ,and charges it up ?

[SMDFlea]

Re: ASUS X550CL - Works only with battery ?

So maybe the "CHARGE MANAGE IC BQ24725ARGRR
TI QFN-20" is the problem ? That doesn't detect the charger ,and charges it up ?

Maybe,you have been probing voltages around it.Put lots of flux around it and solder around all the pins

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

Maybe,you have been probing voltages around it.Put lots of flux around it and solder around all the pins

Did it ,again nothing.
The strange thing is that the laptop working but the mosfets on the side that we said that they should have 19v ,they still don't have.
Even though it's working , i re-tested with new mosfets again doesn't change anything ,and the mosfet still remains dead on the opposite side (both of them)

I removed the chip BQ24725ARGRR, just in case its going to change anything but again nothing ,the mosfet keep doing the same thing.

What can possible make the mosfet not to create the voltage that should create?

[SMDFlea]

Re: ASUS X550CL - Works only with battery ?

You should not start the board up with an IC removed. Why change the mosfets again ? ,the mosfets cannot pass any voltage without voltage on pin 4,it should be 25V ,that voltage comes from PU8802 pin 4.
Test PU8802 voltage on pin 6 and look at the boardview,see what that pin is connected to,test all resistors,look for corrosion .

If you`d prefer to just swap parts then replace PU8802
.

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

You should not start the board up with an IC removed. Why change the mosfets again ? ,the mosfets cannot pass any voltage without voltage on pin 4,it should be 25V ,that voltage comes from PU8802 pin 4.
Test PU8802 voltage on pin 6 and look at the boardview,see what that pin is connected to,test all resistors,look for corrosion .

If you`d prefer to just swap parts then replace PU8802
.

I changed them ,just in case they were the problem.
But again it didn't change anything.
From battery the laptop turns on , detects the battery , but it doens't charge, if you remove it ,it doesn't turn on.

You are saying that PIN4 on the PU8802 ,should be 25V ?

[SMDFlea]

Re: ASUS X550CL - Works only with battery ?

You are saying that PIN4 on the PU8802 ,should be 25V ?

yep

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

yep

It's Zero (0) and the resistor that is connected to PR8809 ,has 4.11K Ohm resistance, but on both sides is zero voltage the PR8809 as well.

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

yep

One question.

Let's say i remove both mosfets , regardless the volt that should stay.

According to datasheet
https://datasheetspdf.com/pdf/1402884/UBIQ/QM3024M3/1

The "D" Drain ,that all pins are as one, should be 19V. which it is ,even the MOSFET if it's removed.

Shouldnt the 2nd MOSFET be 19V as well ? (The "D" Drain)

Or as it is connected,the 19V comes from the first drain ?

[mon2]

Re: ASUS X550CL - Works only with battery ?

No.

Think of each mosfet like a switch or a relay but with no moving part. Actually is much like a water tap.

The turn dial of the water tap controls the flow of the water.

On a mosfet, the GATE lead controls the flow of the current between SOURCE & DRAIN pins.

If the GATE meets the specs for FULL ON, the voltage passes between the SOURCE & DRAIN pins. If the GATE meets the specs for FULL OFF, the SOURCE & DRAIN pins are isolated from each other and there is no flow.

Your logic board has NO mosfets present so do not expect voltage where you are reading 0 volts. However, the 19v on PQ8801 makes sense since the DC adapter interfaces with this side of the mosfet pads FIRST.

If the mosfet is installed AND the GATE voltage is proper to enable the mosfet, then you will see the 19 volts travel to the other side of the mosfet - just like a switch or a relay.

Next, same idea for PQ8802 - the voltage, if present on one side of the mosfet AND the GATE voltage for PQ8802 is present, only then will PQ8802 enable and continue to allow the flow of the 19 volts to the next stage of the logic board.

Consider this to be like 2 relays in series and each relay is controlled individually.

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

No.

Think of each mosfet like a switch or a relay but with no moving part. Actually is much like a water tap.

The turn dial of the water tap controls the flow of the water.

On a mosfet, the GATE lead controls the flow of the current between SOURCE & DRAIN pins.

If the GATE meets the specs for FULL ON, the voltage passes between the SOURCE & DRAIN pins. If the GATE meets the specs for FULL OFF, the SOURCE & DRAIN pins are isolated from each other and there is no flow.

Your logic board has NO mosfets present so do not expect voltage where you are reading 0 volts. However, the 19v on PQ8801 makes sense since the DC adapter interfaces with this side of the mosfet pads FIRST.

If the mosfet is installed AND the GATE voltage is proper to enable the mosfet, then you will see the 19 volts travel to the other side of the mosfet - just like a switch or a relay.

Next, same idea for PQ8802 - the voltage, if present on one side of the mosfet AND the GATE voltage for PQ8802 is present, only then will PQ8802 enable and continue to allow the flow of the 19 volts to the next stage of the logic board.

Consider this to be like 2 relays in series and each relay is controlled individually.

The explanation was really good (learned something extra).

So the MOSFET2 should "get" something to "turn on" the "tap of water to flow current". But it doesn't....
So we begin from MOSFET1 why it doesn't "show" any life.... It has "DRAIN" 19V but the "Source" and "GATE" remain at 0 volt.

So the problem begins earlier than that ? (it's strange for me because it doesn't have anything BEFORE those 2 mosfets")....

[mon2]

Re: ASUS X550CL - Works only with battery ?

Review the voltage of ACDET pin on PU8802 -> pin # 6.

What is the reading with the external power adapter connected ?

[AccountSaver]

Re: ASUS X550CL - Works only with battery ?

Review the voltage of ACDET pin on PU8802 -> pin # 6.

What is the reading with the external power adapter connected ?

With MOSFETS on board.

PIN 1 - 19V
PIN 4 - 0,35V
PIN 6 - 0.1V