Acer V5-551G no power on

[Bad_IC]

Hello,
I have an Acer V5-551G that not powering on, motherboard DA0ZRPMB6C0

PU6:
Pin 16 VIN→19.4V
Pin 11→ 3.3V Pin 20→ 5V
Pin 23 (pgood)→ 0.036V
I've checked 3.3v always on on PL5 and it's ok, and 5v on PL4 ok.

No 3.3V on the power on button...
On the BIOS chip (25Q32Q8SIG) pin 8 no volt.
Checked continuity between bios pin 8 and 3.3V (PL5 inductor) but no continuity...
How is it possible?
Can someone give me some help?
Can i check something else?
Thanks in advance.

[Bad_IC]

Re: Acer V5-551G no power on

Sorry, i've attached the schematic: Acer V5-551 Quanta ZRP DAOZRPPC6C0 RevA1A schematic, because i can't find the right DA0ZRPMB6C0 rev C

[rediii]

Re: Acer V5-551G no power on

check electrolytic caps for 3.3 v and 5 v and 19 v. check power supply.

[mcplslg123]

Re: Acer V5-551G no power on

PL5 stands for +3VPCU-so there cant be direct connectivity between bios chip pin8, which is powered by +3V_S5. +3VPCU becomes +3V_S5 with PQ25.

You need to check working of PQ16/15/14/13/23/24/33/25 to get some clues.

[Bad_IC]

Re: Acer V5-551G no power on

check electrolytic caps for 3.3 v and 5 v and 19 v. check power supply.

Thanks for your reply, the 3.3v 5v and 19v are present.

[rediii]

Re: Acer V5-551G no power on

Thanks for your reply, the 3.3v 5v and 19v are present.

that doesn't mean anything . the device is very old, please check at least the 3.3 v and 5 v caps. sayin' this, because i had similar problems in a few cases

[Bad_IC]

Re: Acer V5-551G no power on

PL5 stands for +3VPCU-so there cant be direct connectivity between bios chip pin8, which is powered by +3V_S5. +3VPCU becomes +3V_S5 with PQ25.

You need to check working of PQ16/15/14/13/23/24/33/25 to get some clues.

Thanks for your reply,
On pin 1 of PQ25 there are 0V and it is connected with BIOS pin 8.
On Pin 3 of PQ25 there are 3.3v...

I've found only
PQ33 drain 3.3v source 0V
PQ23 drain 5.10V source 0V
PQ24 drain 5.10V source 0V
PQ13/14/15 all pins 2 to 9.2v all pins 1 and 3 to ground
PQ16 pin 0?→ 9.2v and continuity to ground ? When check continuity to ground the motherboard led 1 switches on. Is there a problem on PQ16, can be shorted?
Thanks

[Bad_IC]

Re: Acer V5-551G no power on

that doesn't mean anything . the device is very old, please check at least the 3.3 v and 5 v caps. sayin' this, because i had similar problems in a few cases

i've Checked caps:
PC52→ 3,3v
PC46→ 5V

thanks

[mcplslg123]

Re: Acer V5-551G no power on

So this proves that you'll get voltage on pin8 of bios chip only after it turns on-thats how acer has designed it.

PQ16,pin3 at 9.2V is again correct as there is a voltage divider between PR58/59(Both being equal, you will get half the input voltage). So nothing suspicious here.

You should follow @rediii's suggestion to remove those electrolyte caps and replace them with 330uF Tantalum caps. If you have a scope ,no need to remove both this caps and you can check for glitch on output. In the absence of scope, just replace them to rule out a possible issue on relatively old laptops.

The problem lies perhaps in SYS_HWPG. This later becomes HWPG thru an array of diodes. I'll suggest to remove D5/6/7/8 and see if it turns on.Just desolder the diodes on one end only so that you dont loose them and reverse polarity by mistake.

Hope this will help you. Goodluck

[rediii]

Re: Acer V5-551G no power on

Thanks for your reply,
On pin 1 of PQ25 there are 0V and it is connected with BIOS pin 8.
On Pin 3 of PQ25 there are 3.3v...

I've found only
PQ33 drain 3.3v source 0V
PQ23 drain 5.10V source 0V
PQ24 drain 5.10V source 0V
PQ13/14/15 all pins 2 to 9.2v all pins 1 and 3 to ground
PQ16 pin 0?→ 9.2v and continuity to ground ? When check continuity to ground the motherboard led 1 switches on. Is there a problem on PQ16, can be shorted?
Thanks

be careful measuring those diodes and transistors with the multimeter. acer machines are very very sensible at those smds. i had a case where the super i/o got shorted while measuring this thingies. i only had this on acer boards though... please follow mcplslg123 guidance, he is a good guy!

[mcplslg123]

Re: Acer V5-551G no power on

be careful measuring those diodes and transistors with the multimeter. acer machines are very very sensible at those smds. i had a case where the super i/o got shorted while measuring this thingies. i only had this on acer boards though... please follow mcplslg123 guidance, he is a good guy!

@rediii, its not so. You have accidentally touched somewhere. I nver faced any problem in acer in measuring whatsoever component.

[rediii]

Re: Acer V5-551G no power on

@rediii, its not so. You have accidentally touched somewhere. I nver faced any problem in acer in measuring whatsoever component.

i swear i dind't touch anything. i did it a second time just for reproduction. it happened again... was a funny one

[Bad_IC]

Re: Acer V5-551G no power on

I've noticed that on power switch there aren't 3.3v and i think the switch have some problem.
Can't find on motherboard R124 o C156 that are connected with power switch... Jumpered CN10 pin 24 (NBSWON#) to ground and the laptop starts on , but the PL6 and PL7 and GPU chip becomes very hot. After 15 minutes the display goes off
Is it possible there is a GPU problem?
Injected 1v to PL6 it absorb 1.4A...