No Power : Acer Swift 7 Pro (Board model ZDL)

[Benchaton]

Problem : When plugged into power the laptop shows no signs of life but a small periodic tick noise, no battery charging indicator.

Observations :

- The laptop makes a tick sound at regular intervals when plugged in via the charger.

- The laptop negociates with the Power Delivery charger to 20V as expected but shuts back down to 0 then 5 at regular intervals (same as ticking noise)

- 4 Ceramic capacitors have 1 Ohm resistance to ground on both poles (Anotated on the pictures)

- After removal of the Battery Charging IC short is still present (Could have been the cause, it's back in there now. Now being the last thing I did before reassembly of the laptop)

- Injection of 1V @ 5Amps max (Probably a bad idea) shows the short to dissapear on 2 of the 3 tested caps (the two in one circle on the front view of the PCB) as in doesn't pull the max allowed amperage of 5 amps but "only" 3 on one side the other being directly ground still triggers the short light on my Lab PSU. 1 Of the 3 caps (the one circled alone in the front view of the PCB) shows no direct connection to ground on both poles at this amperage and pulls -+2.8, 2.5 amps.

- After power injection multimeter still shows the same shorts even though they weren't there anymore when giving the caps 5amps to eat through.

- MOSFETs seem fine around these caps but I don't really know how to test them

From the last time I had such a problem with an Acer Laptop (Aspire 7736zg) it was a bad MOSFET but I didn't need to find it, searching google was enough because of a thread I found here about the issue. Beware I can only test and give further information on weekends as I'm only free then.

[reformatt]

You should provide the laptop model, and/or motherboard part number at the very least, and links to the schematic/boardview if available. ZDL is insufficient. You need to remove the board and check for it.

At face value, looks like your short is after the 2 DC input FET's, suggesting your main power rail is shorted. Check resistance to ground at the current sense resistor above the BQ chip and go from there.

[Benchaton]

Well, board part number is under a sticker I didn't remove, but exact laptop model / revision is SF714-52T. I didn't provide a boardview because I didn't find any free ones, thought it's on laptop schematics ***********. Also by sensing resistor you mean the big one or the resistor group "the wide" one.

[reformatt]

Motherboard is probably DA0ZDLMBCE0, this should be visible somewhere on the motherboard. No free versions available, but you can request it in the schematics requests forum. It's not exactly new so someone may have it to post. Some cheap options are:

******

Current sense resistor is usually a low value (0.05 ohms for example) 1206 SMD resistor. There are usually 2 on each board, one for the BQ chip the other for the battery. That's a good place to measure for your main power rail. If it's shorted, it's easier to find with a thermal camera if you have access to one. Otherwise, look for discoloured or corroded caps near the edges of the board or near a fan and use voltage injection (1V only) and IPA.

[SMDFlea]

Sorry to be a pain but links to paid schematic sites are against forum rules..

[Benchaton]

Just remembered something I forgot to mention, the inductor has no connections to ground, can't remember the settings I tested with but for sure 200ohms and 2Kohms, which isn't supposed to be the case I'm pretty sure (it already was that way before any injection shenanigans I did). Also if you know better should I inject after the sensing resistor or before (as in higher up in the power circuit), because I tested all caps for connection to ground on both poles coming down from the type C jacks and the battery and only those 4 were "shorted" to ground.

EDIT : Also, from the lesser quality pictures of the board I have, I can confirm that it's a Quanta DA0ZDLMBCE0 - ZDL main board. Watched and read some more about the BQ and Voltage injection, from what I've read if the Mossfets are good nothing went further than the area injected through the caps, a bit more worried about the 1v @ 1.5amps max that went in the inductor which bypassed the BQ's security and thus might have damaged the SoC :/ thing is I can't be sure because I have no schem but geographicly I Hope it's only for the nvme as it's non essentiel and can be swaped though not for cheap.