Original subtitles

Hello way back and this time we have a

nice laptop to repair. This is a Lenovo

Idea Pad Slim 5

and I can see the laptop just hurt.

They are sending me good laptops for

repair.

Anyway, the problem with this one, the

customer open a ticket and he's saying

actually the laptop is powering on or

low life u it has left but doesn't

charge. When checking on inline type-c

meter again is saying 20 volts but no

accepting power. At some point we got 5

volts and accepting power. a gentleman

called Dale and indeed we have a email

and he explained me basically the same

um the same behavior of the laptop. So

what do I think? Can we help Dale?

Charging ports. He sent me charging port

but we don't need them because he said

20 volts. So the PD controller is fine.

The charging port is fine.

But it's very nice to see when uh you

know the customer is sending you even

the charging ports. This is a computer

business by the way. I will say let's

plug the charger and see if it's

charging. Let me take this out

and this. Let me grab a charger. So,

plug in the charger

and

the meter is coming on 19 volts. You can

see there nothing what we can do. No,

the PD controller is fine. No, the fault

is the fault is somewhere else.

Where can we default? On the power

supply which is creating the main power

L and also it's charging the battery.

Yeah, there is the problem.

So let's uh open the laptop quickly. We

seen 20 volts but we know current. Yeah.

Also don't forget this is a Lenovo. Not

sure. I don't think I repaired this

board before.

What screws are here?

Bulanova it's well known having you know

the felling monsters on the board

can be that that issue also

we have a case today like 10 minutes 10

15 minutes ago

uh with a gentleman on discord and he is

saying has a Lenovo he replaced the PD

controller has 20 volts but he's taking

no current. You can see 20 volts in no

current. Then he's attaching the picture

and when I check the picture Yeah.

actually like no MOSFETs. There were not

no MOSFETs on the on the on the

motherboard because the MOSFETs fell

down. Yeah. So he knew where the MOSFETs

are. He said the MOSFETs went to the

ninth dimension.

Okay. Happily. So the MOSFETs are

falling down then you can't find the

MOSFETs. Yeah, I mean those problems are

so common. Of course I advise him to do

like a professional repair and you know

just solder two bridges there and yeah

you fix it. Don't bother with the

MOSFETs and the laptop. It's open.

Yeah, that's a nice motherboard.

But like I said, I uh I don't remember

to see this motherboard before.

So check here. Yeah. Check here. Uh

we spoke we made videos about the Yeah.

Can you spot a coil with four MOSFETs?

No, you can't. Anyway, can you spot a

coil with two dual MOSFETs? Yeah, we

can.

Let me unplug the battery.

You have like a big coil because the

coil creating a main power rail is big.

So you have a big coil with two dual

MOSFETs. You can see there. Yeah.

Yeah, that's the one. Look.

Coil to dual MOSFETs.

Now, let's plug the charger and let's

check the voltage. So, this power supply

has to take the voltage which is coming

from the USBC 20 volts and has to output

the battery voltage.

The meter is coming only 20 volts. Yeah,

but you can't see it. Sorry. The meter

is coming only 20 volts. Let's check the

the voltage at the input of that power

supply. Yeah,

very simple.

So, one is the input, one is the output.

I'm assuming this is the output here.

But the input should be here. And here

we have

here we have 0 volt.

I will say let's go and check under the

microscope. Yeah, we go. I can't see

anything. So under the microscope I

checked there you have the dual MOSFET

then you have a capacitor a current

sensor so definitely here should be 20

and it's not or maybe this is the input

on this case 20 has to be here but it's

not it's 10.5 which is the battery

voltage. Yeah. So this is the output you

can see it's a dual MOSFET has two gates

and this one it's a dual MOSFET has two

gates. So you see the problem is not

even here

and you'll say sorry but yeah but I

don't believe you. I mean you can say a

lot of things which I don't understand

but I still don't believe you. We can

check that. Yeah. So if I'm right

if we are coming with a power supply

with 20 volts on the same point on the

same spot 19 volts. Yeah.

So same spot I said here. Okay.

and

not sure what's what is happening.

What was that? One second. I don't have

current. One second.

Okay, let's try that one more time.

It's taking 3.2 amps and 1.7 volts.

Okay, I take my words back.

Um the the the input is shorted.

But that's how you can check. Yeah. So

we are taking the mind out from the PD

controller. So the PD controller is not

delivering voltage because here is short

right. So here we ground check check the

zero ohms. So here is short.

Then uh of course here is short. Then of

course if you are checking the MOSFETs

because here is ground. If you check the

MOSFET from here to here is short zero

ohms. Check there. So here is something

shorted

but we don't know what. So how we can

find out what is shorted

thermal camera of course

let's bring the the terminal camera

because you'll say n sorry is the moset

is shorted but you don't know that

that's the thing you don't know that and

you cannot assume you have to be sure

I'm not going to replace that moet

uh based on assump assumption so

lowering the the power supply voltage to

like one volt

Okay, a little bit of current

and uh we have the thermal camera.

Great. Coming with current here. Uh

something is getting hot. Check there.

What is that?

Wait, it's a capacitor. One second.

No way. This is a capacitor job. I

really had like high expectation from

this repair because it's coming from a

computer shop and I said must be

complicated

but anyway coming with current here

and what is getting hot

one of this

they're not even cracked you can see

that let me lower the current

so lowering the current now we can spot

better you can See that?

We can spot better.

This one. Wait, which one? This one? No,

it's not this one. Is this one?

It must be this one.

Let's comb with some alcohol

with alcohol here.

So, which capacitor is getting

evaporated? The first one, you can see

the first one is dry already. Yeah. So

that capacitor is gone. Uh what will

happen now is better to not see

but you know say hello to my little

friend. There is one more capacitor. So

we are fine.

What do you think about that? And now if

we are connecting the battery

connecting the charger and the meter is

coming on. Charging light. You can't see

a charging light. It's taking 200

milliamps. That's the pre-charge

current.

Let's wait for the laptop.

200 milliamps.

3.6 amps. See, it's working. I can't

believe. And we cannot use the customer

charging ports because the charging port

is fine. Yeah. The other charging port.

This one. Yeah. Okay.

We have the charging light. is taking

3.6 hours.

I mean we made a video

special dedicated for this case. Yeah.

Like this this scenario this schematic

like you have USBC PD controller then

you have the power supply which is

creating the main power rail and I

explain it's so easy to be found. I mean

you have a coil and two dual MOSFETs. So

you have 20 volts on the PD controller.

It's working. Then you have the power

supply which is creating the main power

and charging the battery on the same

time

and it's not charging. Okay. But I have

20. Why is not charging? Because this

power supply which is creating a main

power is not working. But why is not

working? Because it's not taking the 20

volts from the PD controller because

it's a shorted capacitor at the input.

Yeah. So now if I check uh the output of

this power supply.

So checking the output I said here

and you can see the main power is the

battery voltage and obviously the main

power voltage is going up on the same

way like the battery is charging. Yeah.

And it's working fine. So this power

supply is now outputting a constant

voltage. It's outputting a constant

current. Okay. So just ignore the

laptop. Just think this is the charging

circuit and charging the battery. So it

will provide a constant current. So the

laptop it will take power

from uh from basically this connection

from this power supply to the battery.

Yeah. You disconnect the charger, you

have voltage from the battery, current.

You plug the charger is coming from this

power supply. Really simple. I mean I

don't like the design, don't get me

wrong. It should be better like how it

was before. Just forget about this power

supply and connect the 20 volts from the

PD controller to the main power

and you skip this. Yeah, you skip this.

Skipping this is like you know you lower

the probability to have a fault. You

remember like the old like the old

design old design you don't have this 20

volts straight to the main portal. The

main portal is 20 volts. Then you have a

charging circuit to the battery and

let's say the charging circuit is

getting faulty. You will say okay sorry

if you have the old design the charging

circuit can get faulty can get faulty

but you plug the charger and the laptop

is working with the power from the

charger you still have a working laptop.

I mean I understand it will not charge

but it will still be working.

So yeah like I said every time rising

the complexity you rise the you know

probability to be to have a fold there.

Anyway, I'm happy I held the customer,

Dale, right? Yeah. Yeah, that's the

that's the gentleman. Um, happy I held

them.

We didn't have to replace the the USB

port.

Yeah, it was quite an easy job, so not

sure what shall I say. Well, maybe next

time we'll have a more complicated one.

Anyway, I'm going to stop here. I will

say thank you for watching. you know,

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