Imac A1419 cannot turn on 820 4652 A

[Mohd Salleh Hudin]

iMac Not turn on - Fan spins then stops - LED 2 blinks

Already change new power supply but problem same

RTC signals
PCH_SRTCRST_L - 3.2v
PCH_INTRUDER_L - 3. 1v
PCH_INTVRMEN_L - 3.3v
RTC_RESET_L - 3.3v

 

[2informaticos]

First of all, welcome to the forum!

Check if try to appear all voltages on the big coils.
Be sure no short on any.
Try to start in SMC bypass mode.

 

[Mohd Salleh Hudin]

Already check big coil no short.. Smc bypass nothing happen.. Power 11.96v drop to 9.xxv then normal again

Led 2 blinking and fan spin and stop

Already change ram but problem same

 

[2informaticos]

"Power 11.96v drop to 9.xxv"
Please specify, 12V_G3H, 12V_S5, or 12V_S0???
You may have a problem with Q8450/70.

 

[Mohd Salleh Hudin]

12V_G3H = 12.07v
12V_S5 =12.07v
12V_S0 = 11.96v drop to 9.xxv then 11.96v repeatly

 

[2informaticos]

Then change Q8450...

 

[Mohd Salleh Hudin]

Already change Q8450.. Problem solved.. Imac normal again.. Thanks