Asus C433T not powering on or charging

[Richard_MQ]

Hi All
New member here with a friend's Asus C433T not powering on or charging. No sign of physical or electrical damage, machine was put to sleep one evening and just wouldn't come back on. With charger disconnected, only very small voltages (<1V) anywhere; with charger connected 5V and 3-ish V appear in multiple locations (including battery red & black) but "charge" LED remains Off (as do all others) and power button (and hard reset sequence) have no effect.

Is it possible that the battery is too flat for the charging circuitry to work and for some reason (probably safety, given what these batteries can do...) that prevents charging? I found this thread on Badcaps which suggested similar, and made an initial post there before realising that that sub-forum is for schematics only...

With the battery removed, I measure < 1V between its red and black leads (+ and -). Is it possible to simply connect an external charger there and see if it takes any charge? Or am I likely just to start a fire by doing that? If it is just that the battery is dead, a second-hand one seems to be at least UKP 15 or is it just money wasted?

Thanks
Richard

[Techtiger]

Re: Asus C433T not powering on or charging

Richard, is the Asus C433T disassembled? If so, upload clear pictures of both sides of the motherboard, near the adapter connector there are 2 N-MOSFETs. Is it possible to provide us with the voltage on the Source, Gate, and Drain pins?"

[Richard_MQ]

Re: Asus C433T not powering on or charging

Will take a day or two while I get hold of a USB Microscope but will post back here as soon as I can, thanks.

[Richard_MQ]

Re: Asus C433T not powering on or charging

I'm really struggling to identify the Mosfets - there are very few 3 terminal devices on the board. I can see an Intersil ISL9238 which is an NVDC interface but nothing anywhere near it that looks like a Mosfet to me.

Two pictures uploaded and happy to provide more.

Any advice very welcome please.

Cheers,
Richard

[Sephir0th]

Re: Asus C433T not powering on or charging

Yepp, NVDC. And since you can even measure 3.3V and 5V supplies there is probably no issue in the charging circuit, but later in the sequence. I recommend to share a overview of the board instead. Resistances and voltages of all inductors of the board present. There might be (partial) shorted power rail further down the sequence

[Richard_MQ]

Re: Asus C433T not powering on or charging

I'm reasonably sure I can identify 6 SMT inductors here

Inductor # / Volts / Ohms across / Ohms to GND
1 / 0 (< 5mV) / 0R1 / 330k
2 / 0 (< 5mV) / 0R1 / 8R2
3 / 0 (< 5mV) / 0R1 / 12R
4 / 5.14 V / 0R1 / 53k
5 / 0 (< 5mV) / 0R1 / 24R
6 / 0 (< 5mV) / 0R1 / 630R

(#6 is the one not marked in the photo, close to #2)

Volts measured wrt USB-C shell, with battery connected and USB-C high current charger connected.
Ohms measured with charger and battery disconnected

BTW the reverse side of the board has very few components mounted.

[Richard_MQ]

Re: Asus C433T not powering on or charging

Is a ping allowed on this forum?
Apologies if not...