A1708 820-00875 20v, 0.03A, doesn't power on

[Eduardo&Macs]

Not sure if this is relevant but board came from customer machine that I installed new battery on. This was 3 months ago. They used it two times and on the third time it didn't turn on.

This machine was babied by the owner. The board is super clean, no corrosion, liquid spill or noticeably damaged components.

Tested the charge, it takes 20v and 0.03A. Removed the board and connected to power. Below are the measurements.

USB Meter: 20v 0.03A
20.11v PPDCIN_G3H
0.002v PPVBAT_G3H_CHGR_REG (F7000, C7051, C7050 all show the same)
0.002v PPBUS_G3H (F7000)


What do?

 

[2informaticos]

First of all, welcome to the forum!

Test the board alone on the desk; nothing connected, just USB-C port.
Do you get 3V3_G3H at least (R6999)?
If not check R7020 voltage.

Post U7000 basic voltages; P_IN, VDDA/P, AUX_DET, EN_VR1, SMC_RST*, AUX_OK.

Check diode mode to ground at 3V3_G3H and PPBUS_G3H.

 

[Eduardo&Macs]

Thank you, I'm excited to be here. ?

The readings above were with the board alone on the desk, nothing connected with just USB-C port charger & USB digital tester.

3.422 3v3_G3H @ R6999
20.11 R7020 on all pins


U7000 Voltages:

20.11 P_IN (measured PPDCIN_G3H_CHGR)
5.09 VDDA
5.09 VDDP
5.014 AUX_DET
5.09 EN_VR1 (measured PM_EN_P3V3_G3H)
3.423 SMC_RST (measured SMC_RESET_R_L)
3.423 AUX_OK (measured SMC_AUX_OK)

For Diode mode do I need to measure all components in that circuit? I measured around 10 for each.
Diode Mode:
2.783 3V3_G3H
0.7 PPBUS_G3H

3v3_G3H was strange because it would start at 0.8 then down to 0.7, 0.6, 0.5, shut off and then reappear at 2.783k is that normal?

 

[2informaticos]

No need for diode mode at 3V3_G3H, if already get proper voltage.
BTW, read how to properly check diode mode.

HOW TO collection

I hope this "How to" collection will help our members. I will possibly modify this post in time, if updates available. Trigger SMC_ONOFF_L (PMU_ONOFF_L): It reffers to simulate power button function, when the keyboard is not connected. We need to do this when we work with the board...

boards.rossmanngroup.com

Check BUF_SMC_RESET_L.
Just in case, remove F7000 and check R7060 voltage.

 

[Eduardo&Macs]

I see now. It's meant to check the test points, not the specific components in that circuit. Thank you for that.

3.421 BUF_SMC_RESET_L

Removed F7000
13.06v R7060

Computer now takes 20v with 0A compared to 20v with 0.03A

F7000
13.06v Pin 1
0.00v Pin 2

 

[2informaticos]

"2.783 3V3_G3H"
Read that post carefully.
You cannot get such reading with red probe at ground!

 

[Eduardo&Macs]

I remeasured in diode mode. Red probe at ground. Black probe on test point for 3v3_G3H next to R5168. No power connected. Board by itself on desk.

2.753

Tried putting red probe on USB-C shield, screw holes, RAM shield, etc. All measured the same 2.753.

Tried black probe on 5-8 components that are on 3V3_G3H and all measure the same so far.

 

[2informaticos]

Really strange...
I get 374 in two 00840/75 boards.
Did you check at L6995?
If yes, check if R6999 is not open.

 

[Eduardo&Macs]

Checked L6995.

2.750 Pin 1
2.753 Pin 2

Checked R6999 using continuity mode. Beeps. Doesn't look damaged.

2.740 Pin 1
2.743 Pin 2

I have another 00875 board that takes 20v and 0.05A. I checked L6995 in diode mode. ~2.8
00840 board that takes 5.18v with 0.03A and L6995 in diode mode has ~2.7

Can this be a clue?

 

[2informaticos]

Did you really check in diode mode, or ohm (resistance)?

 

[Eduardo&Macs]

This is so embarrassing. ?

I was using resistance. Switching over to diode mode we get 374.

With F7000 still removed I get 0 on PPBUS_G3H

EDIT:
Reinstalled F7000. I made sure it was installed by using continuity mode and putting each probe on the opposite pads.

Still get 0 on PPBUS_G3H for diode mode.

 

[2informaticos]

"0.7 PPBUS_G3H"
Was this 0hm reading?
0.7 ohm is pure short; 0.700 in diode mode, not at all.
Do you now understand the difference?
You just wasted 2 days with a short on PPBUS_G3H...

Now check if any big coil gives you the same ohm reading like PPBUS_G3H to ground.

 

[Eduardo&Macs]

Yep, I understand now.
0.7 was in Ohms. In diode mode it gives me 0 for PPBUS_G3H

By big coils are you referring to L7030, L7210, L7220 and other “L” components on the board?

 

[2informaticos]

Not L7030, as you get voltage on R7060, when F7000 is removed.
Your problem is after the fuse...