A1708 820-00840-A no power

[hgoncalves]

Hi.

I have an A1708 820-00840-A with no power and no signs of liquid or corrosion.

It has 20V on ampmeter, but only puls 100mA.

No big coil seams to be shorted.

PP5V_S0 = 5V

PP3V3_S0 = 3.3V

PP3V3_G3H = 0V and 0.370 on diode reading

Client said it stoped working overnight.

Can you help?

 

[2informaticos]

How is possible to get S0 voltages without 3V3_G3H?
Please re-check...

 

[hgoncalves]

Hi.

I'm sorry. Not sure how I get those readings.

Actualy, after re-cheking it, PP3V3_G3H starts at 3.4V and then drops to 0V after 2~3 seconds

PP5V_S0 = 0V

PP3V3_S0 = 0V

 

[2informaticos]

USB-C ports stay at 20V when 3V3_G3H drops?
Test the board alone, without battery connected.

 

[hgoncalves]

Hi.

Yes. USB-C stays at 20V when 3V3_G3H drops, and I'm already testing the board alone at the bench.

 

[2informaticos]

That's really strange.
You can't detect any fluctuation at USB-C meter, at same time?
3V3_G3H is required by CD3215 chips to work.

 

[hgoncalves]

Hi.

I've replaced ampmetter. It had some defect.

After re-cheking it, PP3V3_G3H stays steady at 3.4V

PP5V_S0 = 5V

PP3V3_S0 = 3.3V

However, still no power on, and only 0.04A

 

[2informaticos]

If you get S0 voltages, should also get voltage on various big coils.

 

[hgoncalves]

Hi.

L7670 = 5.1V
L7690 = 3.3V
L8410 = 0.010V
L7030 = 12.37V
L7730 = 1.0V
L7430 = 0V and 0.007 on diode reading
L7410 = 0V and 0.007 on diode reading
L7420 = 0V and 0.007 on diode reading
L7210 = 0V and 0.011 on diode reading
L7220 = 0V 0.011 on diode reading
L7370 = 0V 0.016 on diode reading
L8060 = 1.0V
L7900 = 1.0V
L7960 = 0V and 0.118 on diode reading
L8030 = 1.2V

 

[2informaticos]

Try known good BIOS.

 

[hgoncalves]

Hi.

Tried with a new CleanME BIOS, but with same result.

However, now it goes to 0.130A, but still no power on.

 

[2informaticos]

Then bad PCH/CPU...