Acer NITRO 5 AN515-54-52UH Not booting

[mr.Data]

I can use some help figuring out where the problem is. I do not have any schematics.

I do have 19V on the first 2 mosfets but I don't have 3.3V on the BIOS chip.

It seems that I don't have voltage on the (marked in red) 5V and 3.3V power supply, at least I think it must be there.

I have attached images of the motherboard.

What should I measure now to figure out what isn't working?

[volinakis]

Re: Acer NITRO 5 AN515-54-52UH Not booting

Schematic

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

Thank you. I am not able yet to read these but I will look into it and try to figure it out.

[mon2]

Re: Acer NITRO 5 AN515-54-52UH Not booting

Review the power up rail sequence on page # 5 of the shared schematic.

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

I noticed that some capacitors were shorted as marked in red so I desoldered these. After the caps were desoldered there still was a short so I soldered them back on (although not that clean but I fix that later)

After further searching I noticed some of the caps around a chip were shorted as well. The UA1 which appearantly is the HD Audio Codec.

How likely is it that this is the issue?

[mcplslg123]

Re: Acer NITRO 5 AN515-54-52UH Not booting

Measure voltage on pin17 of PU301. If not present, measure resistance on Pin17.
Dont measure directly on IC pin to avoid accidental damage. There should be a cap nearby connected to this pin. Measure on the cap.

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

On the motherboard itself it's a square IC but in the schemetics the IC looks more like a rectangle. How do I know which pin 17 is?

[mon2]

Re: Acer NITRO 5 AN515-54-52UH Not booting

The chip will be square.

Locate the laser etched white dot. That is pin #1 to the left of this dot.

Now count counterclockwise for the next pin, etc.

Being a 20 pin package, each side will have 5 pins.

Post a clear picture of this part on your logic board for verification.

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

I dont understand. On the schematics I count 49 pins. To verify, it's the IC in the image right?

I have marked the pin that needs to be measured with an arrow. Is that the pin we are talking about?

[mon2]

Re: Acer NITRO 5 AN515-54-52UH Not booting

In post # 6 -> the test is of the 3 volt rail on PU301 (not the audio HD codec IC).

PU301 = 20 pin QFN device.

Share a picture of the 20 pin QFN device for a verification.

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

That makes sense. I have measured right after the cap behind the pin which I have marked with a red square.

There was no voltage and the resistance was 0.1 OHm

[mon2]

Re: Acer NITRO 5 AN515-54-52UH Not booting

Yes, this is the IC of interest (PU301).

The capacitor pin that has been measured for the voltage is very likely the GROUND pin so it will be 0 volts and the resistance also sounds correct.

Be sure that when you measure resistance - REMOVE ALL POWER - then meter in resistance mode to take your measurements.

Can you proceed to check the voltage on the other side of this same capacitor?

After this voltage check -> remove all power -> meter in resistance mode.

Check the resistance to ground of this other capacitor pin. Checking to see if there is a possible short on the other pin of this capacitor.

PS: Nice picture. Is this through a microscope or a standard phone camera? Which one do you have?

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

No voltage there. On the other side of the pin its showing 2.4 OHm.
When I put the multimeter on continuity mode it beeps on both sides, this is usually how I figure out there is a short.
Does this means that the IC is probably shorted or can it be that the cap itself is shorted... Or neither of both

I have a microscoop attached to a monitor but the foto's I take are with my Samsung S10

[mon2]

Re: Acer NITRO 5 AN515-54-52UH Not booting

pin its showing 2.4 OHm.

That is a low resistance.

As a quick test, yes, remove this capacitor and check the resistance again but on the actual PCB surface mount pad only to ground. Then we will know if the low resistance is from this capacitor or the IC itself.

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

I first desoldered the IC and measured the cap which dropped from 2.4 to 2, the other side was the same. It was still shorted.

Then I soldered back on the IC and desoldered the cap where the resistance dropped to 1 but still shorted from both sides.

[mon2]

Re: Acer NITRO 5 AN515-54-52UH Not booting

The '1' reading on your meter may be because the reading is actually higher than the meter scale.

Many models of the meter will show '1' to inform the tech that the resistance is higher than the selected meter scale.

Switch the meter scale to a higher resistance scale till you have a reading.

Post the measurements. Even better if you can post the picture of the meter with the measurements.

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

It's an automatic range detector but I put it on manual now and got the exact same readings.

This is measured on the cap from both sides. The one with the highest resistance is the side where the chip is.

Both the IC and the cap is soldered on now. I have measured shortage on the cap itself when it was detached from the motherboard but there was no short.

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

The '1' reading on your meter may be because the reading is actually higher than the meter scale.

Many models of the meter will show '1' to inform the tech that the resistance is higher than the selected meter scale.

Switch the meter scale to a higher resistance scale till you have a reading.

Post the measurements. Even better if you can post the picture of the meter with the measurements.

Does the reading I posted not make any sense?

[mon2]

Re: Acer NITRO 5 AN515-54-52UH Not booting

The readings are good but with a 2R4 (2.4 ohms) value, there is a short.

See the solder blob inside the white rectangle nearby at PJ302. Remove this solder blob to isolate the main LDO rail producer from the load (consumer side). This PJ302 is acting like a short circuit to pass the voltage downstream.

Then check the resistance to ground again of this capacitor.

[mr.Data]

Re: Acer NITRO 5 AN515-54-52UH Not booting

I have desoldered the blob but the resistance stays the same. The short is still there.

At the chip side of the blob there is no short.

This does indicate that the IC is shorted right?