This MOSFET fails a lot.
If is metal case version, remove it and check for corrosion on its pads.
If is metal case version, remove it and check for corrosion on its pads.
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Imac 27 A1419 820-3299a with diag #2 Led flashing.
- Thread starter Scultetus
- Start date
PPVCORE_S0_CPU is not being generated.
I tested the U7100 and the pin "VR_RDY" (PM_PGOOD_REG_CPUCORE_S0) is being pulled low when there is the pulse of energy on the rails.
According to its datasheet (ISL6364), I understood that it would be an OVP or OCP event.
In its PWM outputs, during the pulse, I have a constant pulse of 2.4 V.
Without the CPU the pin "VR_RDY" (PM_PGOOD_REG_CPUCORE_S0) is also being pulled low. I have isolated and tested the phase outputs of the drivers and I have 1.2V constant in phase 1 and 2.4V in phases 2 to 4. This without the presence of PWM signal in the driver inputs, since the U7100 is outputing constant 2,4V. The case is that according to the datasheet, if there is an OVC or OVP the U7100 sends the PWM signal to turn off the drivers (tristate PWM shutdown signal), which should be 2V (maybe it is 2.4V in practice?).
Not sure where the problem is, PWM? Drivers? Others? Am I looking at the wrong place?
I need advice. What should I do now?
I tested the U7100 and the pin "VR_RDY" (PM_PGOOD_REG_CPUCORE_S0) is being pulled low when there is the pulse of energy on the rails.
According to its datasheet (ISL6364), I understood that it would be an OVP or OCP event.
In its PWM outputs, during the pulse, I have a constant pulse of 2.4 V.
Without the CPU the pin "VR_RDY" (PM_PGOOD_REG_CPUCORE_S0) is also being pulled low. I have isolated and tested the phase outputs of the drivers and I have 1.2V constant in phase 1 and 2.4V in phases 2 to 4. This without the presence of PWM signal in the driver inputs, since the U7100 is outputing constant 2,4V. The case is that according to the datasheet, if there is an OVC or OVP the U7100 sends the PWM signal to turn off the drivers (tristate PWM shutdown signal), which should be 2V (maybe it is 2.4V in practice?).
Not sure where the problem is, PWM? Drivers? Others? Am I looking at the wrong place?
I need advice. What should I do now?
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Check all big coils for pulse at same time.
I don't know if that helps, but I talked to the owner of the iMac and he told me that the computer was sent to an assistance before, because it had stopped working once before this, and at that time the repair was done at the bios. He told me also that he took the iMac to that assistance again before giving me the computer, and that they were unable to fix it.
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You can try new BIOS, just in case.
Hopeless project, if came from other service.
God knows what they did there...
Hopeless project, if came from other service.
God knows what they did there...
So now you get all voltages on the board, including VCORE?
Test again with original BIOS.
Test again with original BIOS.
AXG will not appear, unless high graphics load over iGPU.
The new BIOS tried is good for sure?
Then you have nVidia GPU problem...
The new BIOS tried is good for sure?
Then you have nVidia GPU problem...
Sorry, I don't have BIOS for this board.
Maybe other member can help here...
Maybe other member can help here...
I managed to make VCORE work.
Replaced U7100 again.
The board lit LEDs # 1, # 2 and # 3 and chimed.
I was happy because I believed it had been fixed.
But after putting it to work on its own power supply and using the power button, it is again only turning on LEDs 1 and 2.
(By the way, this power supply makes some noise, I don't know if it is normal.)
However, now I have VCORE working and I have on U7100 a high PM_PGOOD_REG_CPUCORE_S0; REG-CPUAXG_PGOOD is still low.
I will review the soldering of the U7100, just in case.
Any idea?
Replaced U7100 again.
The board lit LEDs # 1, # 2 and # 3 and chimed.
I was happy because I believed it had been fixed.
But after putting it to work on its own power supply and using the power button, it is again only turning on LEDs 1 and 2.
(By the way, this power supply makes some noise, I don't know if it is normal.)
However, now I have VCORE working and I have on U7100 a high PM_PGOOD_REG_CPUCORE_S0; REG-CPUAXG_PGOOD is still low.
I will review the soldering of the U7100, just in case.
Any idea?
You should clean ME region, to avoid future problems.