iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

[dg.ott.ca]

Problem: iMac does not turn on, no post, no power, no fan, DEAD

Diagnostic:
Check U7600 for 5V, 3.3V – 0V on both
Check C7650 – 0V, resistance to ground 50Koms (OK)
Check Q6970 pin5 – PP12V_G3H - 11.6V, pin4 FET_EN_P12V_S5_R – 0V (missing enable signal), pin123 PP12V_S5 – 0V (no 12V output to U7600, gate is closed)
Check U6970 pin2 SMC_PM_G2_EN – 0V (missing enable signal from SMC)
Check SMC Power input, C5002 PP3V42_G3H – 3.4V. SMC is powered.

Conclusion:
Main issue, missing signal SMC_PM_G2_EN from SMC to open gate U6970>>>Q6970. SMC is powered but not giving the needed signal.

Solution:
Reflow SMC for 15 minutes (or until it moves). Let it cool down for 30 mins. Connect power supply and check for diagnostic lights. Lights up! IMac is fixed. Call customer and move on to the next one

[koolcat6666]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

Hi,
i have a similar problem on my iMac 21.5 mid 2011.
I'm Italian and im sorry in advance for my bad english.
i will describe the behavior of my mac.
The computer is turning on when it is cold, and it stays on with no problem. if you will shut it off it will not come on until it will cool off.
diagnosing the problem i found this:
led1: Always on
led2: when pushing power button led 2 comes on for a second, fan start spinning, but immediatly goes off, no sound no nothing.
when computer is cold normal post:
led1: Always on
led2: when pushing power button led 2 comes on and stays on, after 2 or 3 seconds led 3 comes on.
led3: after led 2, led 3 comes on and stays on, sound (bong) and video comes on.
led4: comes on after led 3 when computer is on.

can you help me to solve y problem?
thank you very much

Nicola

[gabik111]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

Hi,
i have a similar problem on my iMac 21.5 mid 2011.
I'm Italian and im sorry in advance for my bad english.
i will describe the behavior of my mac.
The computer is turning on when it is cold, and it stays on with no problem. if you will shut it off it will not come on until it will cool off.
diagnosing the problem i found this:
led1: Always on
led2: when pushing power button led 2 comes on for a second, fan start spinning, but immediatly goes off, no sound no nothing.
when computer is cold normal post:
led1: Always on
led2: when pushing power button led 2 comes on and stays on, after 2 or 3 seconds led 3 comes on.
led3: after led 2, led 3 comes on and stays on, sound (bong) and video comes on.
led4: comes on after led 3 when computer is on.

can you help me to solve y problem?
thank you very much

Nicola

Looks like bad power supply.

[angel611]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

Problem: iMac does not turn on, no post, no power, no fan, DEAD

Diagnostic:
Check U7600 for 5V, 3.3V – 0V on both
Check C7650 – 0V, resistance to ground 50Koms (OK)
Check Q6970 pin5 – PP12V_G3H - 11.6V, pin4 FET_EN_P12V_S5_R – 0V (missing enable signal), pin123 PP12V_S5 – 0V (no 12V output to U7600, gate is closed)
Check U6970 pin2 SMC_PM_G2_EN – 0V (missing enable signal from SMC)
Check SMC Power input, C5002 PP3V42_G3H – 3.4V. SMC is powered.

Conclusion:
Main issue, missing signal SMC_PM_G2_EN from SMC to open gate U6970>>>Q6970. SMC is powered but not giving the needed signal.

Solution:
Reflow SMC for 15 minutes (or until it moves). Let it cool down for 30 mins. Connect power supply and check for diagnostic lights. Lights up! IMac is fixed. Call customer and move on to the next one

where is SMC_PM_G2_EN?

[boheman]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

Same problem here and after reflow SMC nothing happened, is it possilbe the SMC is totally dead? And reg_p3v3s5_vout shorted to ground near U7600 Any idea to find the issue?
I replaced U7600 and nothing happened.

[piernov]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

If you have a short to ground on PP3V3_S5 that's what you have to fix, not SMC.
Visually inspect the board for any damage, if nothing inject voltage in PP3V3_S5 and find the component that heats up. Check especially PCH.

[boheman]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

I checked all parts on board, it looks fine and no damage, no touchable heat up, I think I should try it with PSU bench but I never used before.
I will check voltages around PCH.

[mexbeb]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

I have the same board and the same problem, the iMac seems dead.

I had only LED 1 on, LED 2 blinking one time when pressing power button but no power to the board. I was checking voltages on the board and when I was checking U6970 suddenly LED 1 disappeared and voltage from the PS went from 12V to 11.6V (it's still 11.6V now). Also I still have LED 1 off.

Is it possible that when measuring with my DMM a short has been made between pin 1 and pin 2 of U6970 and that PP12V went directly to the SMC (via SMC_PM_G2_EN) frying it? Or is it more plausibly that I have a faulty power supply?

[whirlpool]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

If you have a short to ground on PP3V3_S5 that's what you have to fix, not SMC.
Visually inspect the board for any damage, if nothing inject voltage in PP3V3_S5 and find the component that heats up. Check especially PCH.

I have the same problem. The Mac is completely dead. No lights on the board are on. I used to think it was from the power supply. I changed the power but still the same problem. I have a 12 volt input.

please helppppppppppppppp

[mon2]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

Unplug all power to the chassis and then confirm that the ac plug and socket on the back of the enclosure is reaching the power supply inside.

If you do not see the first led ON then you have no power to the logic board. Could be as simple as a loose power connector.

https://www.ifixit.com/Answers/View/...gnostic+LED+on

[whirlpool]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

Unplug all power to the chassis and then confirm that the ac plug and socket on the back of the enclosure is reaching the power supply inside.

If you do not see the first led ON then you have no power to the logic board. Could be as simple as a loose power connector.

https://www.ifixit.com/Answers/View/...gnostic+LED+on

hi my friend thanks for reply
but I have learned so far the I mac runs on three voltages - 5v, 3.3v and 12v for the inverters.
i have 12 v in pp12v_g3h
i have short in region U2800 this is for gpu
i dont think socket power loose on logic board

[mon2]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

Check the resistance to ground on the polarized caps (tantalums with the "+" or solid white BARs markings) - do this with the power OFF. Like the 330 in your shared pic.

It is ok to have a low resistance to ground on the CPU and GPU as they are low voltage rails but list the values you find.

[whirlpool]

Re: iMac A1418 21 inch 2013/2014 820-3588-A NO POWER, FIXED!

Check the resistance to ground on the polarized caps (tantalums with the "+" or solid white BARs markings) - do this with the power OFF. Like the 330 in your shared pic.

It is ok to have a low resistance to ground on the CPU and GPU as they are low voltage rails but list the values you find.

Thank you very much for being online. I will review the circuit again and send you the report. Thank you very much