Acer LA-G521P Short 3V3

[madjid911]

hI, I have an acer motherboard LA-G521P that won't start, the 3V3 is shorted, I changed the PU401 chip (5X=) and I also changed the microcontroller in short too, now the fan blows very hard, I found the 5V but not the 3V3.

(The micro controller is very well welded, and programmed for the motherboard)

I have no more shorts, the chip PU401 not receive EN2 (0V12);
I have 3V3 on DB1 pin1, but 0V2 pin2, I tested the diode, it is good, so I do not understand why, resistors RB17 = 1Mohms and RB16 = 1Kohms are good.

Can you help me please ? I'm almost there, but not competent enough

I put the diagram, a maintenance document and the brd file if necessary

[Sephir0th]

Re: Acer LA-G521P Short 3V3

PU401 creates 3.3V not only at Pin 3 (LDO) but also at pin 8 (Buck Converter). Which one was shorted before and did you check all enables, outputs for being shorted to GND? It would be helpful when you share exact measurements.

[madjid911]

Re: Acer LA-G521P Short 3V3

PU401 creates 3.3V not only at Pin 3 (LDO) but also at pin 8 (Buck Converter). Which one was shorted before and did you check all enables, outputs for being shorted to GND? It would be helpful when you share exact measurements.

looks like the shorts were on +3VLP (the chip PU401 and UB1 were destroyed

MEASURES :

+19VB : 18V71
+5VLP : 5V17
+5VALWP : 5V17
5V_EN : 3V27
+3VLP : 3V3
3V_EN : 0V3
+3VALW¨: 0V
+3VALP : 0V
MAINPWON : 3V28

I don't understand why I don't have the correct voltage on 3V_EN

[mcplslg123]

Re: Acer LA-G521P Short 3V3

https://www.badcaps.net/forum/showthread.php?t=116394

Read this thread. It may help you.

[madjid911]

Re: Acer LA-G521P Short 3V3

https://www.badcaps.net/forum/showthread.php?t=116394

Read this thread. It may help you.

this is exactly what I wanted to do, shunt DB1 by removing RB16 and 17, but I don't understand why, a thermal protection problem?

So after shunt DB1, I have 3V_EN at 3V3, and therefore I now find the 3V3 on +3VALW, but no start no light no reaction.

I only have 0V2 on the battery +12.6_BATT+, will I have a problem with PU301? Or a power problem with PL402? Value 9 KOHMS