Dell E5550 LA-A911P R.1 ZAM80 - switch on for a second

[rbvndonh]

Hello,

I try to learn laptop repair myself. I have some basic experience.
Laptop is Dell E5550 LA-A911P R.1 ZAM80.
Laptop switch on just for a 1-2 seconds and switch off. No self-restarts.
I can switch on agin, but situation repeat.

PL101 3.3V
PL102 5V
PL700 19.08V
PL701 13.60V

On rest coils 0V jumping up just for a while when i push power button.

I found near pin 4 of PQ200 something like side-melted housing. I found that there is a short between pin 4 and 5 of this chip.

My plan for tomorrow is to unsolder PQ200 and check also PQ201, because now it also show low resistance.
How to check if PU200 also need replace and maybe it is no-brainer when PQ200 is faulty, then PU200 also?
Maybe replace some small resistors/capacitors in it's area also, as i see there is PWR_SRC, so 20V on this line and can go straight on leg PU200?

Plan for tomorrow also:
I found some hint to check Measure voltages on pin 2, 4, 7, 8, 11, 12, 13, 18 of PU200 but don't know what values will be proper one?

2- shall be 0,67V?
4- VDDR ref. As DDR is 1,35V, so there shall be that voltage?
7- 0,675V_DDR_VTT - but DDR is 1,35V, so what i shall get here?
8- _1.35V marked on line
11-5V
12- 5V
13- 1,35V
18 -1,35V

Thank you for hints.

[rbvndonh]

Re: Dell E5550 LA-A911P R.1 ZAM80 - switch on for a second

No luck. It was just resin on PQ200.
Any ideas?

[mon2]

Re: Dell E5550 LA-A911P R.1 ZAM80 - switch on for a second

Remove all power. Meter in resistance mode (2k is ok).

Check each coil on the board for a low resistance value which may indicate a bad cap on that rail which could cause the power supply to shut off as observed. Low resistance = too high of a load and the current sense circuit will trip and disable the switching power supply. Some rails are low voltage and will be with a low resistance but check and post your findings.

[rbvndonh]

Re: Dell E5550 LA-A911P R.1 ZAM80 - switch on for a second

PL101 11,8KR
PL102 22KR
PL200 460R (with RAM module) 591R without RAM
PL301 1,48KR
PL500 44R
PL700 40KR
PL701 3,2KR
I think that values are quite OK. CPU with 44R i5-5300U is OK?

Same behavior on AC adapter and battery only.
PU100 shall be OK, as there is stable 3/5V
PU200 and PQ200 replaced, however between PQ200 and PQ201 connection there is only 550R to ground.
PQ200 and PQ100 sometimes show short (after power disconnected) and sometimes not. Like some protection on board is switched on.
Maybe some PU is malfunction? I hear of some PU700 poor quality soldering. Will look on that tomorrow..

Edit: pic attached. One pin looks poorly soldered. The solder don't look best on one side of chip. Will resolder it tomorrow.