Fujitsu Lifebook A557 power-cycling

[laadya]

Unfortunately, the A555 schematics does not help when it comes to issues I am dealing with in my FSC Lifebook A557 laptop.

The symptoms:
1. The power supply can turn the laptop on, it can charge the battery fully
2. The laptop is power cycling – it flashes the status LEDs and can hold the wi-fi + power-on LEDs on, it spins the fan for approx. 5 secs. After 20-30 secs it turns off and immediately on again with the same pattern
3. When “running”, I also found out that 2 of the 3 USB3 ports on the right side of the laptop do not work - the third one does (5V present, meanwhile for the 2 not being on)
4. Even being sceptic about possible outcome, I also flashed the BIOS (out of the board) – yes, with no impact

I focused to the Vcore, since I consider this the core of the problem.

The measurements (see the photo):
a. Voltages:
i. The main power rail of 19V is up
ii. The rails of 1.2 / 3.42 / 5 volts are also up
iii. There is no voltage present in the red circle
iv. There is 6.11V in the blue circle
v. There is steady 1V in the green circle
b. Resistances on the 4 coils, from left to right:
i. 16 ohms (green circle)
ii. 16 ohms
iii. 35 ohms
iv. 11 ohms (all three in the red circle)

Any advice how to proceed with repair is hearthily welcome. 😊

Thank you.

[mcplslg123]

Re: Fujitsu Lifebook A557 power-cycling

Ram is onboard? IF not, try replacing ram stick. Does the mb remains on when ram removed? 1.8V/2.5V present(assuming ddr4 is used)? DRAMRST# rises for the brief time when it remains on?

[laadya]

Re: Fujitsu Lifebook A557 power-cycling

Thank you for the ideas.

Yes, RAM is in and no change observed. Three sticks tested.

I would like to search for the DRAM RST signal, however I do not have schematics of the board available. The A555 (FH9) schematics found here does not match the A557 (FH9U) layout, so hard to track something down.

I will continue searching.

[laadya]

Re: Fujitsu Lifebook A557 power-cycling

I also found more users observed very similar troubles with the A557. See this link in the FSC forum:
https://forum.ts.fujitsu.com/forum/v...c.php?p=154275

Would like to know what the guy mentioned as the one who succeeded repairing the laptop had done.

[mcplslg123]

Re: Fujitsu Lifebook A557 power-cycling

Should be DRAM_RST# = 1.2V PIN 108 as long as the ram is DDR4.

[laadya]

Re: Fujitsu Lifebook A557 power-cycling

Thank you a lot for your support.

There on PIN 108 (which I believe is THE pin, since without schematics it is hard to be sure - I derived it from some video on YT) is just 1.1-1.2 milivolts, and not the expected 1.2V. I checked it with 2 different sticks in both slots individually and then both of them populated.

Now we are getting somewhere it seems. So please can I ask you what to do next? How to get those needed 1,2V on this PIN back?

Thank you.

[mon2]

Re: Fujitsu Lifebook A557 power-cycling

Remove all power. Meter in resistance mode.

Measure the resistance to ground of this missing power rail.

Post the measurement.

Next, switch the meter to diode mode.

Red meter probe, yes red to ground.
Black meter probe to this missing power rail.

What is the diode mode measurement?

Each check must be without power to the logic board.

[Sephir0th]

Re: Fujitsu Lifebook A557 power-cycling

In my opinion there is no point to look at DRAM_RST# when it is Stuck so early in the sequence: The CPU isn't powered at all. And from my experience DRAM_RST# usually isn't routed to the EC. So if you want to check this line, then check at the memory connector itself, pinout is standardised.

However, 1Volts and 16 Ohms at the coil circled in Green at the same time is probably bad luck since it is likely the +1.05VALW for the PCH. Points into the direction if a partial shorted PCH in my opinion.

[mcplslg123]

Re: Fujitsu Lifebook A557 power-cycling

@Sephir0th is right. DRAMRST# will come later. I asked whether 1.8V/2.5V is present or not and you didnt answered that. Its very difficult to conclude PCh is defective with a resistance of 16 Ohms as we all have seen resistance even lower then this on 1V rail and mb seems working.