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820-02098 Stuck at 5v

prodigy83

prodigy83

Member
My reference only: TT10031
Board history is unknown. Everything looks clean, no visible liquid damage.
USB-C meter is stuck at 5v. I have isolated the issue to PPBUS_AON by removing F5200/01.
When both fuses are removed I get 12.59v on PPVBAT_AON_CHGR_REG, but on the PPBUS_AON I get 1.42 which slowly drops.
When these fuses are back on, I get 6.78v something is pulling it down, .93 amps are being drawn according to the USB-C meter and U8100 is getting quite hot with fuses back in place. It seems like I got a problem with PPBUS_AON but I cannot figure out what the problem is.
 
2informaticos

2informaticos

Administrator
Staff member
Check diode mode to ground on all secondary power supplies.
Check on U7700 and U8100 LDOs and coils too.
 
prodigy83

prodigy83

Member
2informaticos said:
Check diode mode to ground on all secondary power supplies.
Click to expand...
Could you provide me an example of a secondary power supply on this board? Keep the fuses on while checking using diode mode?
So far... Fuses still on, L8280 using diode mode shows .003v.
 
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prodigy83

prodigy83

Member
Gotcha.
In the interim I did find a short coming from UR200, I have replaced it and the Diode mode reading is now .267. CPU still dead?
Looks like the link you sent me is now the correct reading. Thank you for sharing that, this is super helpful. Do you have a list of links or tools you have compiled that I could bookmark here as well?
Forgot to mention this board still stuck at the 5 volts.
 
prodigy83

prodigy83

Member
R5710 is at 5.1 volts, seems a bit too high?
R5712 pin 2 jumps to 1.8 when plugging in the usb-c meter but goes to 0 right away. Pin 1 is at 5 volts.
148 degrees Fahrenheit on U8100.
The row of capacitors above U5700 seem to be out of character for how they are supposed to look. I will include a picture. This is also measuring in diode mode @ that .066.
Below images show U8100, and that row of capacitors above U5700. Is U8100 fried? What do you think?
img20231213_113845.jpegresized-1003120231213104247370.jpg
 
prodigy83

prodigy83

Member
Removed that row of caps and the diode mode reading is .062.
When I remove F5200/01, I get 12.27v on PPVBAT_AON_CHGR_REG, however when the 2 fuses are placed back on, I get 7v. Something is pulling the voltage down.
 
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prodigy83

prodigy83

Member
I get 4.3m but it just keeps falling lower and lower. I had already removed Q5240 when taking this measurement. Should I redo with it back on? I also do not have another board.
With Q5240 still removed, pins 11 and 12 are O/L, openboarddata shows this is not correct. The other pins using diode mode seem to be close enough when measuring.
CHGR_AUX_DET_3V3 I get 0 volts. Then with diode mode I get .620. I have the two fuses off F5200/01.
When I remove the fuses, I get the 12.26volts (PPBUS_AON), but when the fuses are on, it drops to 6volts.
I did also replace both U5200 and Q5240.
 
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2informaticos

2informaticos

Administrator
Staff member
If you get 12.26V at C5250 removing F5200/1, then your problem is on the other side of the fuses (system side, PPBUS_AON).
 
prodigy83

prodigy83

Member
Yes, I see that. I just don't know where else to go or how to track this down further. There are a bunch of resistors. U5700? 0 volts at pin 8 for U5700.
Diode mode .472 on PPVIN_P3V8AON_ISNS. Thats not too far off is it? Fuses are still off.

With fuses back on, PPVIN_P3V8AON_ISNS is 6.129volts

Diode mode: PP5V_AON_P3V8AON .511 looks good.
P3V8AON_PVCC .553 looks good.
P3V8AON_PWR_EN_R .585 looks good.
P3V8AON_LPM_R .679 spot on.
PP5V_AON_P3V8AON .518 looks good.
P3V8AON_FAULT_L .694 looks good.
P3V8AON_IMON_P3V8AON .775 looks good.
P3V8AON_GPIO .695 looks good.
P3V8AON_SS .749 looks off, supposed to be .694. I am getting .282 volts.
Am I looking in the right area?
 
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prodigy83

prodigy83

Member
3V8_AON voltage is: 1.48volts.
Sorry, I must have been editing my post when you wrote in. Here are my findings to your question and more I did:
With fuses back on, PPVIN_P3V8AON_ISNS is 6.129volts

Diode mode: PP5V_AON_P3V8AON .511 looks good.
P3V8AON_PVCC .553 looks good.
P3V8AON_PWR_EN_R .585 looks good.
P3V8AON_LPM_R .679 spot on.
PP5V_AON_P3V8AON .518 looks good.
P3V8AON_FAULT_L .694 looks good.
P3V8AON_IMON_P3V8AON .775 looks good.
P3V8AON_GPIO .695 looks good.
P3V8AON_SS .749 looks off, supposed to be .694. I am getting .282 volts.
Am I looking in the right area?
 
prodigy83

prodigy83

Member
No dice, I had a donor board with the same chip, swapped it out, no change, the U8100 chips is still heating up. I did reach back out to the customer to get further clarification on the problem and this is what he told me:
The computer was working fine with no issues. I use it for work and it's usually on about 8 hrs a day. When I returned home I decided to update Ventura. I think it was OS 13.4, I clicked update and walked away. Upon returning the computer was dark and unresponsive. There was nothing plugged into the computer, no peripherals, no power as the battery was fully charged.
 
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prodigy83

prodigy83

Member
Okay, trying to isolate the problem I have removed the following in this order: rd503, rd591, rd590. As soon as I removed I got 12.26v back on pin 2. Pin 4 and pin 3 were at first pulsing 1.4v to 1.5 but now those same pins are .500 thru .200 volts.
Yea, measuring again, it has gotta be on the PPVIN_P3V8AON_ISNS side of things. Maybe my donor board chip u5700 was bad, not sure. I will try to isolate the problem further.
Another update: I removed U5700 again, and I am now getting 3.8v at rd590 pin 1, so this is indeed a bad U5700?
Another update: I decided to remove Q5840, Q5820, and Q5800. When I did this, PPVIN_P3V8AON_ISNS went back to the 12.6v. R5840 seems to be a connection somewhere here.
Update: P3V8AON_SW1 I am getting 1.46v, and diode mode reads .025, should be .356. I have already replaced, and reflowed U5700. Bad Q5800?
Just replaced Q8500 and now I have a short to ground on P3V8AON_VSW1. When I inject voltage the U8100 chip gets warm just like it always has. Any other ideas?
Hope you had a great holiday(s) by the way.
 
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prodigy83

prodigy83

Member
The above message I left edited on this past Saturday but I see responses to other peoples posts as recent as of today, could I get a response please?
 
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