820-3787-a

[Bunuffin]

Hello

I have orange light on the charger, get 20v at the u7100 DCIN, i have 1 volt on ppbus_g3h even without the u7100 on the board, don't see any short on the coils

I replaced the u7100 since it was blown.

 

[2informaticos]

First of all, welcome to the forum!

What is the diode mode to ground reading on PPBUS_G3H?
Check resistance (ohm scale) between pins 17/18, 19/20 and 27/28 of U7100.

 

[Bunuffin]

Ppbus has no continuity
17/18=3ohm
19/20=4.8ohm
27/28=4.9kohm

Ps: these measures were made without the u7100 being on the board

 

[2informaticos]

"27/28=4.9kohm"
Fix the problem; check R7121/22 and their traces.

"Ppbus has no continuity"
I didn't ask that...

 

[Bunuffin]

"What is the diode mode to ground reading on PPBUS_G3H?"
I get 0L reading on my multimeter, sorry I miss read...

I have tested the rails and I don't see disconnects or high ohm.

I see 778ohm across R7121 and 3.9khom across R7122.

I'm sorry but I'm a noob so please be patient with me

 

[2informaticos]

Resistors value marked on the schematic.
Seems that both are bad in this case.

"I get 0L reading on my multimeter"
Learn how to properly use the multimeter in 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

 

[Bunuffin]

I'm gonna get me the schematic, board viewer it's not enough, will scavenge resistors from the donor, then I will report.

This is my reading, reverse is the same, it reads something for a second then I get this...

 

[2informaticos]

Be aware of using auto mode on multimeter; select proper scale.
Do not make confusion between ohm and diode...

 

[Bunuffin]

Ok so, diode mode gives me 0.444v with positive on ground, 2.315v with negative on ground...

 

[2informaticos]

These are correct values; doesn't seem to have any problem with PPBUS_G3H rail.
Just fix R7121/22 problem...

 

[Bunuffin]

Am I reading it right? Both are 0ohm resistors right?

 

[2informaticos]

I would say 10 ohm, as per schematic.
However, even 0 ohm will work...

 

[Bunuffin]

Oh yeah I see the 10, sorry

 

[Bunuffin]

Perfect, fan spin and picture... God bless you, I learned so much.

Thanks!