Acer Aspire 5920 no power, ticking sound

[Dannyx]

Good day folks. I just busted my Aspire 5920 while working on it. Truth be told, it's entirely my fault because I wanted to install a bluetooth module and in doing so, I powered it up with the case open to see if it works and one of the SMA connectors for the wi-fi antennas dangled around and touched the motherboard somewhere and the laptop shut down....I know, I'm an idiot

Now it's not doing anything....like AT ALL ! No power light, no nothing. There is however a faint clicking sound coming from the area I pictured up close at around 2 second intervals...something obviously died, but with so many components it's tough to tell what could've gone wrong, especially since I didn't see exactly what that connector touched and there are no burn marks or visible signs of damage. The input fuse is OK and I couldn't find any shorts, at least with the brief measurements I took...

Hopefully some laptop mavericks out there have encountered this issue or at least have some general idea of what I should be looking for....VERY difficult fix I imagine. I attached the schematic. Sorry if the pictures are not great - I took them in a hurry.

The reason I'm hanging on to this laptop, since it's a piece of junk by today's standards, no doubt about it, is because it's not technically mine - it's the laptop from my workplace and I'm really disappointed I broke it in such a stupid way, despite my superiors not caring about it and not charging me anything for the damage at all. Cheers and thanks.

[piernov]

Re: Acer Aspire 5920 no power, ticking sound

At the center of the picture is the charger IC. If the clicking sounds come from here, you may have an issue on the B+ line (called VIN on the schematics) at least.
Check the voltage on this line and its resistance to ground.
If it's there, check what you get on +3VPCU and +5VPCU.

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

I'm not getting any shorts to GND from what I recall, though additional testing is required. You mean PU1 ISL-something on page 32 of the schematic I assume

[dellxps15]

Re: Acer Aspire 5920 no power, ticking sound

on the 3rd picture there is the winbond ec. check if it get hot when power plugged in. if it get hot replace it.

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

As far as I remember, no, nothing gets even warm, plus if you mean the large IC under the plastic sheet (which is indeed a Winbond), that calls for a replacement motherboard right there. Not because I don't know how to replace it, but because I wouldn't be able to find one, at least not cheap I reckon and also because the effort would outweigh the price of a replacement board. Still, I don't think that's the issue, since my brief knowledge tells me that at least the "AC in" LED should've come on...there's a "VCC" issue somewhere IMO.

[dellxps15]

Re: Acer Aspire 5920 no power, ticking sound

that winbond costs 1.5€ i replaced many on 5920g . they fail very easlily. another thing that fail is the fds6990 near psu plug

if winbond dont get hot then it should be fine. focus on 19 volt rail .

check if 3.3 5 volts are present, check voltages on charger ic.


u dont have any light on power botton when connecting power supply ?

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

No, no light whatsoever. I located the trannies you're talking about, though they're not exactly that: they're FDD6685 in my case. They're not shorted. Could the ISL itself be faulty ? What exactly is generating the 3.3v and 5v rails ?

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

Another thing I remember is that there's a large electrolytic PC88 in the area we assume is faulty. When I measured it, the voltage goes from 0 to around 18v in time with those clicks (can't remember exactly whether the reading is present when the click is heard or in-between clicks). Thought I'd mention this too. The power adapter's voltage is steady all throughout though - it never cuts out or dips.

[dellxps15]

Re: Acer Aspire 5920 no power, ticking sound

from the last picture, more to the left there is 8 pin fds6990. check voltage there too,

3.3 and 5 volts generated from opposite side of the board, near front leds. 2 coils are for that volts. check them.

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

Found the area you're talking about: bottom-left corner of the board, underneath the express card slot. I limited my searches close to the area around where the power jack is connected, but apparently the power circuit is spread all over the board, all the way to the opposite corner. I assume I should measure the positive leg of caps PC76 and PC78 for what they call 3.3vPCU and 5vPCU. Looks like a buck converter topology based on knowledge of electronics.

[dellxps15]

Re: Acer Aspire 5920 no power, ticking sound

check 3.3 and 5 volts there on red marked zone.

edit: ofcourse negative on a metal place...

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

Yes, I believe it's the same thing, since those caps also connect to those coils - typical buck converter

[piernov]

Re: Acer Aspire 5920 no power, ticking sound

Yes, those are synchronous buck converters, as it is almost always the case for generating the various power rails. (sometimes when the rail only needs a very low current - like standby power for EC - it is generated by an LDO)

So you have pulsing VIN rail? Sounds like an over-current situation to me.
But first please write down the exact voltage you get on those coils (with pulsing if applicable).
Also write the exact voltage of VIN line (with pulsing if applicable).

Btw the boardview for this motherboard should be available on the web. Try to find it, it'll help you to locate the components.

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

Here's what I measured: PC78 gives me 5v on its + leg, so I am getting 5v.
However, PC76 gives me nothing, so I have no 3.3v.
Also, PC88 (which I believe is connected to VIN) goes up to 18.23v WHEN I hear the ticking sound then slowly drops down as the cap discharges and the cycle repeats with each tick. So no 3.3v, yet I couldn't identify any shorts still...

[caspian]

Re: Acer Aspire 5920 no power, ticking sound

measure resistance on the two pins of PC88 once without power and once with power connected. I mean one probe on one pin and the other probe on the other pin.

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

Resistance is around 20m ohms+ and dropping slowly as the cap charges up - definitely no short there, as the meter would pick it up instantly.

Now with power connected to the board, if I put the plus probe on the negative leg and the minus probe on the positive leg, the meter beeps and I get 0 resistance (ONLY with power connected, not otherwise), however the clicking sound made by the board also becomes quicker now, like 2 times a second so I don't think it likes that. If I put positive to positive and negative to negative (either on the chassis or on the negative leg of the cap, since it's the same thing), I get random readings and the "low battery" symbol shows up on my meter, so it's not quite liking that either...

[caspian]

Re: Acer Aspire 5920 no power, ticking sound

replace PC88. It is just a good try.

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

replace PC88. It is just a good try.

The cap ? Could a cap just go poof like that ?

[caspian]

Re: Acer Aspire 5920 no power, ticking sound

I do not know if the main problem originates from PC88. But I think PC88 should be replaced since it seems kind of damaged on the upper side.

[Dannyx]

Re: Acer Aspire 5920 no power, ticking sound

I doubt it's damaged in any way - would've definitely shown some signs of failure until now. I'm tracking down that VIN line trying to figure out what's loading it and causing it to shut down, but can't find any shorts....I already ordered another board, since they're relatively cheap, this being an old model, but it would be nice if I could fix this one as well to hopefully make up for at least some of the money spent on buying the replacement one