iMac A1311 PSU 614-0444

[thevolt]

Hello, I am hoping someone can point me in the right direction in fixing the power supply on my mid 2011 21.5" iMac (A1311). The onboard diagnostic LED lights 1 and 2 do not light up when plugged in and powered on. The iMac turns on but does not get passed a black screen. For the past year if turned off the computer would not boot up unless I unplugged the power cord for a few hours. This past week I was updating to 10.13 Sierra and it shut down and will not get passed a black screen now. I pulled the PSU, but everything seems to visually look clean. Attached are some pictures. I really don't feel like buying a new PSU for almost $200 on a computer I do not use very much. If anyone has had an experience in dealing with these PSU's and can pass on any suggestions I would appreciate that. Thanks in advance. -Jay

[thevolt]

Re: iMac A1311 PSU 614-0444

The 5 capacitors are KZH 1500uf 16v. Should I start by replacing those 5. Is there any suggestions for a better brand of that style of capacitor? Or should I be looking somewhere else on the PSU?

[PeteS in CA]

Re: iMac A1311 PSU 614-0444

I'd look into whether or not it has the equivalent of a 5VSB or 12VSB. If it should but does not, that is where your problem is rather than those output capacitors. If you have no standby voltage, look at small lower voltage electrolytics on the primary side.

[patrik1998]

Re: iMac A1311 PSU 614-0444

"Hi help I need to fix an iMac with the same PS board, damaged by a lightning strike. When I opened it, the board wasn't working at all: I replaced two burned SMD resistors and two capacitors, and the iMac came back to life. But after a short time it became to shut down and restart by itself... I guess I misread the value of some burned component, replacing it with the wrong one(s). Can you please . me? They are R003, R004, C009 and C010. Many thanks in advance!"

[Siddig]

Re: iMac A1311 PSU 614-0444

I have problem in same PS board . I have change it burn big capister . I get 2v in 12v pin.
Can you help me

[sena_akutsa]

Re: iMac A1311 PSU 614-0444

..." Can you please . me? They are R003, R004, C009 and C010. Many thanks in advance!"

R003 "331" = 330 ohm
R004 "331" = 330 ohm
C009 = 25 nF
C010 = 25 nF

[jantoman]

Re: iMac A1311 PSU 614-0444

Same iMac, 21,5" Mid-2011. I'm trying to fix an issue with an on/off flashing backlight, everything else seems to work.
These are the voltages I measured on the PS 14-pins connector:

pins 1, 3, 5, 7, 8, 14: ground
pin 2: +3,3 volts
pin 4: +12 volts
pin 6: nothing
pin 9: +3,3 volts
pin 10, 11, 12, 13: +10,50 volts

Pin 13 is connected to the inverter input, that is marked 12 volts: there's definitely something wrong.

[aavs]

Re: iMac A1311 PSU 614-0444

i have a problem with an a1311 source and needed help. This is always oscillating the standby 12V, 10V, 11V, 12V, standby pin ... and input 380V, 398, 392, 380 in the high voltage capacitor, all capacitores are ok.... I suspect the pwm.

[jantoman]

Re: iMac A1311 PSU 614-0444

Hi. I found out that in my power supply one of two MOSFETs near the output plug was shorted... That's why I couldn't get a correct 12v rail for the inverter. I replaced both MOSFETs and now everything works fine.

[leerumbles]

Re: iMac A1311 PSU 614-0444

Hi. I found out that in my power supply one of two MOSFETs near the output plug was shorted... That's why I couldn't get a correct 12v rail for the inverter. I replaced both MOSFETs and now everything works fine.

Can you tell me which MOSFETS you purchased? I believe I have the same problem. The MOSFETS are etched with 85T03GP and the only replacements I can locate are from China. Thank you.

[lfmacmor]

Re: iMac A1311 PSU 614-0444

HI, I have a problem with an a1311 source and needed help. This is always oscillating the standby 12V, 10V, 11V, 12V, standby pin, any solution.?