820-2915-B PPBus_G3H=1.2V

Hello.

I have this 820-2915-B, no power. It takes 270mA from the PSU and GPU gets hot.

PPBus_G3H=1.2V
PPBus_G3H= 6 ohms to ground.

I have 0.2ohm between F7040 and L8920. Any advice?


Thanks!
 
After removing Q8950 the short is gone. Unfortunately I do not have one to replace it.

If I disable the GPU (using dosdude method) could I leave the board without that Mosfet?
 
Client needs the Dedicated GPU. I bought a donor board, replaced Q8950 and when turning on the GPU gets ultra hot and the board takes 4A.
I imagine death GPU? Can replace the 216-0810084 with a 216-081005?
 

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You've changed Q8950 and powered up the board without checking anything else on the GPU power supply?
If you change GPU and do the same, you'll probably fry the new GPU too.

If you want to use 216-081005, then move R8610 to R8612 and solder 10K resistor in place of R8613.
 
What else should I have mesured?
With Q8950 removed I powered up the board, green light but obviously no video. Measured all coils and nothing extrange found. PPBus_G3H= 12v.

What is the normal voltage value of PPVCORE_GPU?

Currently I have the GPU out, what should I measure?
 

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Q8950 got burnt because of some reason.
Possibly bad C8956, or U8900.
Can also be broken traces, or bad solders.
Better to change Q8950/51 and U8900 at same time.
 
You were right. I was getting 3V on PPVCORE_GPU_REG_R.

Replaced Q8950/51, C8956 and U8900 and now I have 1.1V on PPVCORE_GPU_REG_R (Is this ok?).

Currently not GPU Soldered. What else should I measure before installing GPU?
 

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You should consider disabling GPU for such old machine.

Now GPU can be soldered if you want.
Its core voltage looks good.
 
Hello.
Customer insists on the dedicated GPU.

I have replaced GPU ( moved R8610 to R8612 and soldered 10K resistor in place of R8613 since I am using a 216-081005). But I am not getting
PPVCORE_S0_CPU.

PPVCORE_S0_CPU: 0V
PP5V_S0: 5V
CPUIMVP_VR_ON: 0V
PP1V05_S0: 0V
CPUVCCIOS0_EN: 3V
 
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1V05_S0 must appear before CPU core voltage.
This also causes missing ALL_SYS_PWRGD.
So fix the problem on U7600 area first.
Check diode mode to ground at L7630.
Post U7600 voltage; pins 13, 14, 3.
 
Removed Q7950 and still ALL_SYS_PWRGD: 0V.

Can you explain the ALL_SYS_PWRGD?
I need all of the yellow voltages to create ALL_SYS_PWRGD right (see attached)?? U7960 is no present on the Board.

P5VS3_PGOOD: 0V (I replaced U7201 and same)
P1V5S0_PGOOD: 0V
 

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You should remove the resistors from ALL_SYS_PWRGD (one by one), until found which power supply cause the problem.
Keep R7967 in place; hope it has 3V at pin 1.

U7960 is not used...
 
U7100 was the problem. Now the board power up, the screen is white but never shows the folder (with thunderbolt)
Black screen with its screen.
It chimes
Could be Bios since I changed the GPU 084 for one 081005? Could you provide good bios file?
 
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Did you configure VRAM resistors correctly?
Do you get external video?
Caps Lock light reacts, USB activity?

Internal LCD is pure white, or classic Apple grey?
Did you try another LCD assembly?
 
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