Acer aspire 5920 short circuit

[scooby01]

Hi My acer aspire 5920 has a short. I can not see any visible damage on the pcb. The charger led just flashes when I insert it. Has anyone come across this and what ip may be the cause.
Thanks

[Dimitrios]

Re: Acer aspire 5920 short circuit

I have experienced this issue! I was lucky I just had to remove battery and then insert chargers plug. Try it. Is your charger official with tip diameter 5.5mm x 1.7mm?

[scooby01]

Re: Acer aspire 5920 short circuit

Thanks for the response. I found the issue, capacitor p033 had gone short circuit. Replaced now fine. hope this may help someone in the future, it is under the wifi card.

[dj_ricoh]

Re: Acer aspire 5920 short circuit

how do ppl find bad caps(SMD) omg.
i understand that others inject voltage but damm where?
no pics?

[Th3_uN1Qu3]

Re: Acer aspire 5920 short circuit

There are multiple ways, the quickest and most entertaining one being using a low voltage, high current supply (1 volt max, to not damage any chips), and 10A or more... The problem will be where the smoke comes from.

[Ozito]

Re: Acer aspire 5920 short circuit

Would 5A be too insufficient?

[fikus]

Re: Acer aspire 5920 short circuit

There are multiple ways, the quickest and most entertaining one being using a low voltage, high current supply (1 volt max, to not damage any chips), and 10A or more... The problem will be where the smoke comes from.

Thanks!

[dj_ricoh]

Re: Acer aspire 5920 short circuit

There are multiple ways, the quickest and most entertaining one being using a low voltage, high current supply (1 volt max, to not damage any chips), and 10A or more... The problem will be where the smoke comes from.

The problem is that I got a cheap PSU ( you saw it on the Logitech tread).

It can go max 5 amp and its not adjustable. It takes only how much it needs.
Now I see why need a pro PSU.
Dammm

[rievax_60]

Re: Acer aspire 5920 short circuit

Keep in mind that what might look like a short on the +Vbat rail might be a shorted HighSide Mosfet in one of the Buck regulators. So whatever voltage you apply to the +Vbat is actually being applied to the CPU, GPU, NB or RAM.
This is a reason to not exceed 1 volt.
I find shorted caps using only 0.5A and measure voltage drops with a Fluke 85V in HiRes mode. Bit hard to explain though.

[dj_ricoh]

Re: Acer aspire 5920 short circuit

Keep in mind that what might look like a short on the +Vbat rail might be a shorted HighSide Mosfet in one of the Buck regulators. So whatever voltage you apply to the +Vbat is actually being applied to the CPU, GPU, NB or RAM.
This is a reason to not exceed 1 volt.
I find shorted caps using only 0.5A and measure voltage drops with a Fluke 85V in HiRes mode. Bit hard to explain though.

does it drop from 1v to 0.7 and stay there or it just drop from 1v to 0.something (like droping droping)

[Th3_uN1Qu3]

Re: Acer aspire 5920 short circuit

You can make a high-current low voltage supply out of a dead video card, use the core VRM.

[rievax_60]

Re: Acer aspire 5920 short circuit

does it drop from 1v to 0.7 and stay there or it just drop from 1v to 0.something (like droping droping)

By "voltage drop" I mean the usually very small voltage difference that develops along the length of a conductor that has a current flowing through it.
For example, where the probes are shown positioned in the photo, I got a reading of 0.12mv. The capacitor is shorted circuited with 0.5A of test current flowing through it.
I measure the voltage drop on various parts of the ground plain to get close to the shorted part.

[opamp]

Re: Acer aspire 5920 short circuit

You can make a high-current low voltage supply out of a dead video card, use the core VRM.

Have you made one? what would be the output current?

[3d0]

Re: Acer aspire 5920 short circuit

Would it be possible to use a computer PSU and modify it for such low voltage and current. There's a bunch of videos on youtube, but they solder all the +5, +12 cables together and get 20A or more on them. Would a PSU be safe enough for this kind of work?
Has anyone here made his on bench supply?

[Th3_uN1Qu3]

Re: Acer aspire 5920 short circuit

An unmodified computer PSU cannot produce this low voltage. By removing turns from the transformer and replacing the voltage reference, yes, it would be possible.

[rievax_60]

Re: Acer aspire 5920 short circuit

Keep in mind that what might look like a short on the +Vbat rail might be a shorted HighSide Mosfet in one of the Buck regulators. So whatever voltage you apply to the +Vbat is actually being applied to the CPU, GPU, NB or RAM.
This is a reason to not exceed 1 volt.
I find shorted caps using only 0.5A and measure voltage drops with a Fluke 85V in HiRes mode. Bit hard to explain though.

That should read "Fluke 87V". For the HiRes mode.

[Th3_uN1Qu3]

Re: Acer aspire 5920 short circuit

Another way of locating shorts (or at least narrowing down on them), is isolating the individual blocks of the board.

It is highly recommended you have a schematic for this. It's very hard (but not impossible) to do this without one. First remove everything from the board. RAM, CPU, Wifi, etc. If it is still shorted, follow:

• Follow the rail that you find shorted on the schematic.
• Look for jumpers and/or inductors connecting that rail to the rest of the circuit. Unsolder jumpers/remove inductors.
• Check which end of the jumper/inductor still shows a short.
• Repeat until you isolate the short to just one block.
• Test MOSFETs on that block.
• If you found shorted ones, replace them.
• Remove all large ceramic caps.
• Short cleared? Congrats. Replace caps, put the inductors back in, resolder the jumpers and you're good to go.

I have just fixed an Acer Aspire 5315 by this method, B+ was short to ground. A large ceramic cap in the battery charger circuit was responsible for the short.

[rievax_60]

Re: Acer aspire 5920 short circuit

This photo shows voltage readings at and near the shorted capacitor that I found today in a Dell.
The high cost of the 87V takes some of the fun out of this method though.

[dellxps15]

Re: Acer aspire 5920 short circuit

hi, when u talk about jumpers u are referring to dell mainboard? on many acer (quanta mainboard i have not seen any jumper.)

ps: have a acer 5920g with some short problem.

different problem but we can compare our voltage.


once i had a asus laptop. when inserting psu in it it turns off for some time till i think it coem back from protection. it was the flat cable plus some corrosion on the board.

Another way of locating shorts (or at least narrowing down on them), is isolating the individual blocks of the board.

It is highly recommended you have a schematic for this. It's very hard (but not impossible) to do this without one. First remove everything from the board. RAM, CPU, Wifi, etc. If it is still shorted, follow:

• Follow the rail that you find shorted on the schematic.
• Look for jumpers and/or inductors connecting that rail to the rest of the circuit. Unsolder jumpers/remove inductors.
• Check which end of the jumper/inductor still shows a short.
• Repeat until you isolate the short to just one block.
• Test MOSFETs on that block.
• If you found shorted ones, replace them.
• Remove all large ceramic caps.
• Short cleared? Congrats. Replace caps, put the inductors back in, resolder the jumpers and you're good to go.

I have just fixed an Acer Aspire 5315 by this method, B+ was short to ground. A large ceramic cap in the battery charger circuit was responsible for the short.

[senndogg]

Re: Acer aspire 5920 short circuit

i use a standard 12V 7Ah sealed battery and a 60W hi beam car lamp for gaining a 5A current. typically after 4 seconds the responsible cap goes on smoke.
but please pay attention to the B+ contact. find a thick trace somewhere near the battery controller or you risk seriously damaging the mainboard.