820-00840 with shorted PP3V3_G3H

sekidata

Member
Liquid damaged 820-00840 board with 35Ω to ground on PP3V3_G3H. With plugged-in charger, I get 3.3V on PP3V3_G3H and 20V.

When I inject 3V into PP3V3_G3H, the SMC warms up. Probably a shorted SMC, agreed?
 

2informaticos

Administrator
Staff member
Not really short, as you get even correct voltage.
But very low resistance for that power rail.
Do you note another hot spot on the board?

Check resistance to ground at C5010/21.
 

sekidata

Member
C5010: 4kΩ to ground
C5021: 2MΩ to ground

Hard to say if anything else heats up b/c the injection only draws 0.1A and I don't have thermal imaging.
 

sekidata

Member
The machine actually starts in its current state, but runs super slow. Apple Diagnostics report SMC and PM errors (PFM006 and PPN001).
 

2informaticos

Administrator
Staff member
Very likely problems with trackpad flex/board.
Battery may be involved too.

Try first to disconnect battery and reconnect it after 10 minutes.
If still same problem, test with known good trackpad.
 

sekidata

Member
I installed this board in a different, known-good topcase. Same issues: throttled performance and fan on high speed. PP3V3_G3H still 33Ω to ground.
 

2informaticos

Administrator
Staff member
Check AVREF_SMC voltage.

You may need to change the SMC.
Once removed, check diode mode to ground at 3V3_G3H power rail.
 

sekidata

Member
Removed the SMC and short has disappeared (diode mode reading 0.350).

Do you have a suggestion on how to get started on reballing? Source for stencils and materials for Apple boards?
 

2informaticos

Administrator
Staff member
You can't reball a dead chip!
Do you think wooden foot massage helps for something???

Get another SMC from donor board, same model.
Aliexpress has necesary stencils for any kind of SMC.
Just do NOT buy flux there; avoid "chinese honey" use on repair process.

I personally reball with solder paste and direct heat stencil.
Many videos available on Internet; practice on scrap boards/chips...
 

sekidata

Member
Of course I was implying that I would get an SMC from a donor board.

Thanks for the tips on what tools to get. I'll give it a go!
 

2informaticos

Administrator
Staff member
Isn't that flux?
Don't buy flux on Aliexpress.
You can do the job even with cheap "chinese honey", but I don't recommend it at all.
I use ECOFREC TF49.

You may find more sellers on Aliexpress.

I still use chinese solder paste.
Buy in small recipients 35-50g.
Not very expensive and much better quality here:
 
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