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A1706 no power

2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

As you've said, USB-C meter is a must have.
Until you get it, tell us actual PPBUS_G3H and 3V3_G3V voltages; only charger, battery disconnected.
If any missing, check diode mode on that rail.

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 boards.rossmanngroup.com

I recommend you to practice soldering on similar scrap boards; before touching any board you plan to repair.
 
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students_t

Member
Thanks! I've ordered the USB-C meter from your store. I opened the case and disconnected the battery.

I have basically zero background in this, so I am trying to find some kind of explicit example of things before I do them. I the case of the actual PPBUS_G3H actual voltage, I used this video (
- link includes timestamp to 10min30sec; close up of contact point also shown at 12min40sec here
) to figure out where to place the multimeter probes. I found a voltage of 0.002 V.

For 3V3_G3V I am having some problems (sorry). I tried to find a schematic that might help me figure this out (I found one at the following link but I am pretty sure it is not the exact board I have despite it being for the same A1706 model of macbook https://www.badcaps.net/forum/troub...hematics-for-820-00239-a-macbook-pro-touchbar). I guess the board number should be written on the board somewhere? I tried searching a bit to try to figure out where, but no success yet. I installed openboardview to be able to look at the .brd file. However, I couldn't find anything about "3V3_G3V" when searching the .pdf of the schematic and the .brd file component list. I'm sure this is some super basic thing that I ought to be able to figure out, but when I do an explicit phrase Google search for "3V3_G3V" I actually only get this forum thread as a result (https://www.google.com/search?q="3V3_G3V")... is there a typo there? Sorry; I'm sure there should be some straightforward way to figure this out, but I haven't found it yet and worry that I'm not looking in the right places.
 
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students_t

Member
Thanks! I have been extremely busy with work-related travel and have not been able to work on this, but I have more time now and will move forward with figuring out the 3V3_G3H voltage. Also, I received the USB-C meter, so if that opens up additional tests that I should be doing, please advise.
 

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students_t

Member
OK, I followed this video tutorial for removing the board (
), and on the underside (relative to my perspective as I was removing the board) I found "820-00239-A" on the board. Where to from here?
 
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students_t

Member
Excellent; thank you. Using the board viewer program I found, I am able to locate the various 3V3_G3H positions... I think. The board viewer has entries for "P3V3G3H_FB" and similar; not sure why the "P" prefix and different underscore convention, but if this is actually the correct thing, then the image in my last post (which shows the board number) also shows P3V3G3H_FB. There are multiple P3V3G3H_* items listed in the .brd file. So my next job is to get the voltages at each such 3V3_G3H contact vs. ground?

Or, actually, I just looked a little more exhaustively through things. I found PP3V3_G3H listed in the .brd file. Is this actually the right one? One of the files attached shows this with the various spots highlighted. I see there are two contact points for PP3V3_G3H plus other things highlighted when I select PP3V3_G3H from the "Net List". I also see in the PDF on page 100 a schematic for the "3V3 G3H Rails"; I infer that the small numbers at the ends of the lines on the schematic are the pages in the PDF to go to for seeing where this continues. So... go to e.g. where one of the attached pictures says "TP[1]PP3V3_G3H" and measure voltage vs ground? Or do something more exhaustive?
 

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students_t

Member
OK, great, I found that position and I checked the voltage relative to ground using red probe contact with the "top" (relative to the orientation in the schematic screenshot attached) side of L6900 and black probe contact with the edge one of the holes through the board for screws that go around one of the fans: 0.000 V. When I recheck PPBUS_G3H I also get 0.000 V. Is there a voltage I can check somewhere that will give a non-zero value just so I can confirm that I am making proper contact? When I make contact for measuring PPBUS_G3H or PP3V3_G3H I do briefly see a reading in the range of roughly 0 ± 0.007 V, but this quickly converges to zero. However, I notice that this brief initial divergence from zero happens when I contact the red probe to metal that is not even associated with the board, so I assume this is just the nature of the meter/reading that these values briefly appear.
 

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2informaticos

2informaticos

Administrator
Staff member
Are you checking voltage (charger connected), or just diode mode (no charger, no battery)?
For voltage, always black probe connected to ground.
For diode mode, red probe connected to ground; rarely need to check in reverse way.

BTW, allow 10-15s before diode mode, or ohm scale checking, once any power was removed.
 
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students_t

Member
Ah yes, I lost track of things and derped out--was doing voltage mode without charger connected. Running diode mode, I get 0.365 V for PPBUS_G3H and 0.331 V for PP3V3_G3H.
 
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students_t

Member
In order to connect to power and check the voltages, I will need to re-attach my board to the case, right? Is there a way to minimize how much I reconnect? Like, can I just reconnect the USB ports on one side or something? Or is that bad practice?
 
2informaticos

2informaticos

Administrator
Staff member
Remove the USB-C connector and use it on the desk.

You should get such connectors from Aliexpress, or scrap machines; is a must have on the workshop.
 
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students_t

Member
Here is the reading on the usb-c meter. Edit: The image is from when it first turned on. The temperature reading rose to like 23 °C over time.
 

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