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Model A1311 / Late 2009 / 3.06 or 3.33 GHz Core 2 Duo 프로세서

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iMac won't boot (probable bad PSU)

I have an iMac 21.5” (Late 2009 - EMC 2308) which won’t boot; completely dead. I believe the PSU is dead. I am hoping someone can confirm/refute that conclusion.


I searched for a pinout of the PSU but could find none. I followed the Apple Diagnostic workflow for “No Power; Dead Unit” with the following results at the Logic Board Test Points:


Test #1 - Pin #1 -> Pin #4 - LED #1 lights and 12vdc is detected when plugged in

Test #2 - Press PWR Button - LED #2 not lit, 0vdc at Pin #12 and no startup when power button pressed

Test #3 - Disconnected power button and tested for continuity - continuity is present

(also tried jumping PWR pins on logic board where button connects - same result)

Test #4 - Pin #1 -> Pin #11 - 12vdc present, whether or not power button is pressed

I conclude, from this, that the PSU is bad. If anyone has a pinout for this PSU (661-5299 or 614-0445) or can shed more persepective on this problem, I’d very much appreciate any insight that you can offer. In any case, thanks for the time and energy you spent reading this

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Here’s how to replace it:

iMac Intel 21.5" EMC 2308 Power Supply Replacement

Apple part numbers, will work 661-5299, 614-0444

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Sincere thanks, mayer, for suggesting the proper replacement method. I found a refurbished and tested replacement PSU and installed it - no change at all in the system behavior. All results are the same as the original.

I went through the Logic Board Test Points with a multimeter and measured its resultant voltages. System conditions are as listed in my OP:

Pin #1 - 0vdc (Ground)

Pin #2 - 0vdc

Pin #3 - 0vdc

Pin #4 - 12vdc

Pin #5 - 0vdc

Pin #6 - 0vdc

Pin #7 - 0vdc

Pin #8 - 0vdc

Pin #9 - 0vdc

Pin #10 - 12vdc

Pin #11 - 12vdc <--- Even when system is off

Pin #12 - 12vdc

Pin #13 - 12vdc

Pin #14 - 0vdc

I have no pinout for PSU and cannot verify spec voltages, but the fact that both the original and the replacement measure and behave similarly seems to point elsewhere. And the presence of voltage at pin #11 while off seems aberrant. This would seem to point to the logic board. Can anyone confirm or refute this conclusion? Again, mayer, thanks for your help and many thanks to that of any other contributors.

11-19-2020 - UPDATE - I got a warranted, used logic board and installed it this afternoon with the following results:

• The iMac now powers up.

• LED #1 and LED #2 light up, indicating that there is power to the logic board.

• The device emits a “no memory” beep if no RAM is installed.

• There is no system chime or other sound when RAM is installed.

• The fans run at full speed until the system is powered down.

• There is no video at all.

• An external monitor, connected using the DisplayPort, displays no video.

I tore it down completely, checked every connection and reassembled it with the same result. I noted that the vertical sync cable looks sketchy; the cable’s lamination is parting in one place (close to the logic board end) and the contacts on that end look adequate but not perfect. That is the only sign of physical irregularity I can find.

Any insight would be appreciated and, whether or not, many thanks for the time and energy you spent reading this.

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