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820-2849-A no chime PPBUS_G3H intermittent 8.33v/1.9v

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protocold

Member
I have a 820-2849-A with no chime. When I plug in magsafe, it will have greenlight(sometime greenlight comes on after a few seconds delay).
Sometime fan will spin and PPBUS_G3H around 8.33-8.35v, when fan spin, it will spin with varying speed like high and low, high and low.... at random pattern.
Sometime fan will not spin and PPBUS_G3H is about 1.9v or 3.9x and then keep droping to 2.x

u7000 pin 2 15.8v
27/28 resistence 21ohm
17/18 resistence 3.6ohm

PP5V_S5/S3/S0 is ok,
PP3V3_S5/S3/S0 is ok
PP1V8_S0 is ok
PP1V5_S3/S0 is ok
PPCPUDDR_ISNS is ok
PP1V2_S0 is ok


The following seems to be abnormal:

PPVCORE_S0_CPU 0.43V ???
PPVCORE_S0_GFX 0.87V ???

PPVCORE_S0_CPU_VCAP0 0.03V??
PPVCORE_S0_CPU_VCAP1 0.03V??
PPVCORE_S0_CPU_VCAP2 1.04V??

Battery can charge (orange light).

Seems like someone tried to replace SMC and also U7000 as I have seen flux around them.

what should I look?
 
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2informaticos

2informaticos

Administrator
Staff member
Post some basic voltages for U7000; pins 1, 2, 3, 6, 9, 12, 13, 14, 15, 17, 19, 20, 27.
Especially when PPBUS_G3H goes low...
 
P

protocold

Member
changed Q7080. Still pretty much the same, the fan still has speed high and low... and PPBUS_G3H is still high and low as before.


Here is the reading of the U7000 now (when PPBUS_G3H is at 8.33v)
pinV
10
215.88
33.89
60
90.54
123.4
133.4
143.23
150.06
178.35
195
205
2716.42

I actually when the PPBUS_G3H go low.. pin 1 would have 15.32v. Somehow when PPBUS_G3H is at 8.33v, pin 1 would have 0v (chgr_agate_div will have 6.71v). Is that normal?
 
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2informaticos

2informaticos

Administrator
Staff member
Measurements when PPBUS_G3H is correct, don't help.
Change Q7085 now.

Leakage on Q7080/85 is a common cause for that symptom.
Measure R7085/86 onboard, ohm scale.

In this case could be other reason, but you should discard input MOSFETs first.

Remove F7040/41 and check if R7050 voltage is steady.
 
P

protocold

Member
changed Q7085. I dont have new HAT1128R01. So the replacement of Q7085/Q7080 comes from donor board. I hope they dont bring the same problem...

R7086 - 338K.

R7085 - 478K

Removed F7040/41, R7050 voltage steady at 8.35v
 
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P

protocold

Member
According to Louis powerpoint slides... ".... old Macbook Pro 17? PPBUS_G3H is 8.5v when the SMC is able to communicate with the ISL, 8.16v when the SMC cannot" Mine is neither.. do I have SMC problem?
 
2informaticos

2informaticos

Administrator
Staff member
8.35V is good enough.
Exact voltage depends of multimeter type and slightly varies from board to board.

If PPBUS_G3H goes down in normal mode, means SMC detects a power issue and cycles power.
Resolder the fuses and check what happens with 3V3_S5.
Post diode mode to ground on all big coils.
 
P

protocold

Member
Did you mean PP3V3_S5? It is 3.3v.

Sorry i am a noob, when you say all big coils, did you mean these?

Coil diode mode reading to ground
L9710 444
L7795 427
L7260 306
L7220 328
L7031 337
L7030 337
L8020 003
L7425 010
L7415 010
L7630 005
L7330 144
L9560 83
 
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P

protocold

Member
L9710 0v
L7795 2.16V
L7260 3.3V
L7220 5V
L7031 8.35V
L7030 8.42V
L8920 .0.4V
L7425 0.1V
L7415 0.1V
L7630 1.06V
L7330 1.48V
L9560 1.83V
L9510 1.07V
 
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P

protocold

Member
2informaticos said:
Any voltage at L9510?
Click to expand...
sorry when i measure those voltage, PPBUS_G3H was at 8.35v. L9510 = 1.07v, I have updated the above for completeness.

However, when i got PPBUS_G3H to go low, the readings became:

PPBUS_G3H is pulsing between 2.5v and drop to 1.82v and then jump back to 2.5v (in repeat)

L9710 0v
L7795 0
L7260 0V
L7220 0V
L7031 pulsing between 2.5v and drop to 1.82V
L7030 pulsing between 2.5v and drop to 1.82V
L8920 0V
L7425 0V
L7415 0V
L7630 0V
L7330 0V
L9560 0V
L9510 0V

PPDCIN_G3H is 16.8v


2informaticos said:
I cannot find L8020; do you mean L8920?
Click to expand...
Yes, sorry, I mean L8920. I have corrected above.

PPBUS_G3H seems to remain intermittent, I cannot reliably reproduce high and low, sometimes it is just high and then sometimes it is just low.
 
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2informaticos

2informaticos

Administrator
Staff member
Any reason to quote an entire post visible few centimeters above???

Please, maintain forum aesthetic...

You have a problem with GPU power supply.
 
P

protocold

Member
I am sorry about the quotes...

thanks for the pointer, i just checked that R8911 was missing! I just shorted this with solder and now L8920 has 0.91v. However, now the fan suddenly stopped.
 
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D

dukefawks

Administrator
R8911 did not "just" go missing. My guess is that the GPU is shorted and someone messed with it and disabled GPU power by removing that resistor and possibly doing a BIOS mod to let it run on Intel only.

Also some of these boards do need a battery connected or PPBUS will intermittently not come up.
 
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