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820-00928a not turning on

C

chedda

New member
Hi,

I'll try to list everything I know so far:
  1. Draws ~1.1A @ 20V when powered (without battery)
  2. Draws ~330mA @ 20V when turned of with power button
    1. Kind of high right? but nothing gets hot, checked with IR camera
  3. All _s0 power rails present
  4. Tried flashing 4 different bios images found on this board, no change
  5. Only once the boot logo was visible after SMC reset
    1. After that, the fans were always running at max
    2. Now after probing on some smc lines, the fans run normal (gradually revving up, but not to max)
  6. No chime, caps lock light, usb activity, Touch Bar, external video
  7. Trackpad clicks
  8. No voltage drop at ppvcc_s0_cpu, stays at ~1.05V
  9. smc bypass mode won't work
  10. No reaction on multimeter or otherwise when trying PRAM reset
  11. History not known, but I can see it was worked on
    1. A line is soldered from R6001[2] to it's probe point (SMC_FAN_0_CTL) slightly below

Where to go from here?
 
2informaticos

2informaticos

Administrator
Staff member
330mA for a board in S5 state, is really high.
You should find the reason.
Remove F7000 and check again the current.
 
C

chedda

New member
At the top I said, all power rails present, but actually PPBUS_G3H was 12.59V, which is ok for other boards, but not this, right?
Now after removing the fuses, the usb-c multimeter says 350mA @20V and PPBUS_G3H is still 12.59V.
When measuring PPDCIN_G3H_CHGR I get 21.2V although the usb-c multimeter actually says 19.3V. Don't know if that's significant.
I measured around the ISL9239 and got these values:
Gate_Q4: 0V
LX2: 0V
Boot2: 5V
Gate_Q3: 5V
Gate_Q2: 5V
Boot2: 5V
LX1: 0V
Gate_Q1: 0V
No shorts to ground on the caps.
On L7030 I get 0.02V on both sides.

Are these values normal. Sorry for asking basic stuff. I don't have a working A1707.
 
2informaticos

2informaticos

Administrator
Staff member
You still have high current without the fuses.
I can suppose a problem through 3V3_G3H power rail.
Some chip sinks too much current there probably.
Could be SMC, or PCH.
 
C

chedda

New member
Without the fuses the PCH stays cold and the SMC is barely (~1°C) warmer then room temperature.
With the fuses the PCH gets almost as hot as the CPU. The SMC stays as before.
Any way to rule out or confine without blindly replacing those two?
 
2informaticos

2informaticos

Administrator
Staff member
In such case, you should have bigger current difference between the two cases; w/ and w/o fuses on board.
 
C

chedda

New member
Sorry, that wasn't clear. The PCH only gets hot when it's trying to turn on. When I turn it off by pressing the power button, it's as if the fuses were removed, except without fuses it's drawing 20mA more.
 
C

chedda

New member
Yes.
Also, when I do an SMC reset, the current goes down to 350mA (like without fuses) while pressing the key combo and after letting go. Than it won't turn on (draw more amps) anymore unless I replug the charger.
 
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