Laptop Zenbook UX480 Fuse L

[corrize]

Hello, on this laptop, there is a black fuse 0603 with letter « L », it is blow up (close LVDS connector). I can't find it nor equivalent on alixpress. Can you help pls ?

[corrize]

Re: Laptop Zenbook UX480 Fuse L

Maybe, it’s this one.

https://fr.aliexpress.com/item/4000812956401.html

The 1.75A ?

[hardware1]

Re: Laptop Zenbook UX480 Fuse L

Hello, on this laptop, there is a black fuse 0603 with letter « L », it is blow up (close LVDS connector). I can’t find it nor equivalent on alixpress. Can you help pls ?

I think it should be that one (0603, 1.75A, 32V).
If you can't find it, you can use (0603, 2A, 32V) with letter (N), it's the closest one.

Also you must measure and see if there's any short to ground before or after the fuse.

[mon2]

Re: Laptop Zenbook UX480 Fuse L

Can you post a pic of the area where this fuse is on the logic board?

In comparing a mix of other Asus logic board, there is a polyswitch fuse of 0.5A in 0603 package. Also found 0.75A in 0805 package on a few boards.

P/N SMD0603P050TF

So the concern is on the actual rating of the component.

Also, if you really had a polyswitch fuse onboard then that fuse will reset after a period of time once the power and excessive load event is removed.

[corrize]

Re: Laptop Zenbook UX480 Fuse L

Thx for reply, I will order it so.
It’s not a reset fuse, the laptop is off long time ago.
It’s a screen fuse, see picture, it is below, at left of LVDS connector

[mon2]

Re: Laptop Zenbook UX480 Fuse L

Actually, a "P" means Polyswitch / polymer switch. They self-heal after a period of time. If the fuse has a lot of wear then yes, the fuse will no longer self-heal.

Remove all power. Check the resistance across the fuse pads.

To me, the part looks larger than an 0603 -> perhaps a 1206 size?

https://www.aliexpress.com/item/32804658202.html

https://p-nt-www-amazon-ca-kalias.am.../dp/B0B6DJBPBT

1206 SMD fuse with code K:

https://www.littelfuse.com/media?res...206l-datasheet

To check the size:

a) measure it with a micrometer

OR

b) review that the part beside is a SOT23-6 device. Hunt down any part in SOT23-6 package and review the length of the part.

Then compare the fuse length to validate if the fuse is 0603 / 0805 or 1206.

My bet is on 1206.

[SMDFlea]

Re: Laptop Zenbook UX480 Fuse L

Actually, a "P" means Polyswitch / polymer switch. They self-heal after a period of time. If the fuse has a lot of wear then yes, the fuse will no longer self-heal.

I don`t think it is. The forward slanted P is the logo for Polytronics

[mon2]

Re: Laptop Zenbook UX480 Fuse L

Well noted. Still shows up a PPTC.

https://www.pttc.com.tw/smd.aspx

[SMDFlea]

Re: Laptop Zenbook UX480 Fuse L

Still shows up a PPTC.

It does

1206 Marking K SMD1206P010TF/30

0603 SLR series Marking K SMD0603P050SLR

0805 SLR series Marking L SMD0805P200SLRT ,it could be a different part from a different manufacturer though

The datasheets are quite good,each one has a useful cross reference

[corrize]

Re: Laptop Zenbook UX480 Fuse L

The fuse marked « P.. » is good, I saw it, I know what it is now.

There is another issue.

I plugged the laptop, no light, nothing.
19v ok at first mosfets, and 24v at gates
+5v and 3.3v présents

but when I plug the battery (empty), no charging. At the coil closest : 0.86v, it should be 12v ou 15v (battery charge voltage). I guess the charging chip is dead.
19v present feeding this charging chip but voltages around the chip are low.

I noticed that often the charging chips can be dead but not shorted. Have you a tips for quickly check if the chip is dead pls (without check all voltages) ?

[mon2]

Re: Laptop Zenbook UX480 Fuse L

Which charger IC is onboard?

Review the HIGH side mosfet that is linked to the charging of the battery. The charger makes use of 2 external mosfets to 'dial' down the voltage from the 19v main power leg.

Respectively, both of these mosfets - high and low side must switch on/off to provide a desirable charge voltage.

Remove all power -> meter in resistance mode.

Check the resistance of each of the battery charger mosfets:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement.

On the battery, connect the adapter and measure the voltage to ground of each of the battery pin connector. Interested in the SMBUS SCL and SDA voltage readings.

[corrize]

Re: Laptop Zenbook UX480 Fuse L

The chip is BQ24780S

I guess the mosfets are good because there is 19v at drain (of the first mosfet) and 0.86v at gate and I saw 0.86v at a component a the out of the charging chip. So mosfets provide 0.86v because there is only 0.86v at gate

The values of mosfets :

Mosfet 1
source (1-2-3) & drain (5-6-7-8) : 33 MOhms
source (1-2-3) & gate (4) : 180 K
gate (4) & drain (5-6-7-8) : 20 M

Mosfet 2
source (1-2-3) & drain (5-6-7-8) : 5.5M
source (1-2-3) & gate (4) : 156 K
gate (4) & drain (5-6-7-8) : 3.6 M

I can't understand why the battery connector values are useful ? That should be the same than the mosfets provide ?

[corrize]

Re: Laptop Zenbook UX480 Fuse L

The measurements of the charging IC : BQ24780S (DC jack plugged, battery unplugged)
The chip is dead ?

1 - ACN : 19v
2 - ACP : 19v
3 - CMSRC : 18.8v
4 - ACDRV : 24.6v
5 – ACOK : 5.94v
6 – ACDET : 2.62v
7 – IADP : 0v

8 – DCHG : 0v
9 – PMON : 0v
10 – PROCHOT : 0v
11 – SDA : 3.29v
12 – SCL : 3.29v
13 – CMPIN : 0.17v
14 - CMPOUT : 6v

15 – BATPRES : 0v
16 – TB_STAT : 0.16v
17 – BATSRC : 0.86v
18 – BATDRV : 0.89v
19 - SRN : 0.86v
20 – SRP : 0.86v
21 –ILIM :1.16v

22 - GND : 0v
23 - LODRV : 0V
24 - REGN : 6v
25 - BTST : 5.8v
26 - HIDRV : 0.86v
27 : PHASE : 0.86v
28 : VCC : 19.04v

[mon2]

Re: Laptop Zenbook UX480 Fuse L

I can't understand why the battery connector values are useful ?

On the battery, connect the adapter and measure the voltage to ground of each of the battery pin connector. Interested in the SMBUS SCL and SDA voltage readings.

..

[corrize]

Re: Laptop Zenbook UX480 Fuse L

OK, found. It's a basic data bus (battery speaking with charging chip I guess ?)
I measured 3.27v at the SCL and SDA pins of charging chip, and at the white and yellow wires on the connector of battery (plugged and the adapter too).
0v at the + of battery

[corrize]

Re: Laptop Zenbook UX480 Fuse L

Found this bad guy close the audio amp chip, it's shorted ; 0 Ohms. I will remove it tomorrow but I dont know the value (no schematics for this model). And I guess it's not the issue, I already find a shorted cap on the main power rail on this board and there is no coil shorted.

[corrize]

Re: Laptop Zenbook UX480 Fuse L

Not the guilty, I compared to another board very similar (UX481) and it’s an inductor and not a capacitor, so it’s is good. So, back to the charging chip.

[Sephir0th]

Re: Laptop Zenbook UX480 Fuse L

Since the charging controller asserted ACOK and a few secondary power rails are present, I'd more suspect fault later in the sequence.

I didnunderstood it like, even without battery the board isn't coming on, so...

[corrize]

Re: Laptop Zenbook UX480 Fuse L

So what pls ? What do you mean ?

Do you supect a little component after the charging chip or a main big chip ?

The original issue for this laptop was a bad cap close the dual mosfet of CPU VRM. But the dual mosfet is not shorted and after replace the cap, no short nowhere but oxydation at some places. I guess the CPU is ok, and I see no reason to suspect Super IO or chipset (even I was expecting a light on after plug the adapter).

[corrize]

Re: Laptop Zenbook UX480 Fuse L

I have a new way. Around a 5E= chip, a resistor without any resistance (oxydation) and 3 caps shorted so I will see that…