PSU providing enough voltage?

Question

iMac Intel 24" EMC 2134 und 2211

Model A1225 / Mitte 2007 und Anfang 2008 / Core 2 Duo Prozessor mit 2,4 /2,8/3,06 GHz

434 Fragen Alle anzeigen

Nate @nate47251

Rep: 13

1

Veröffentlicht: 27. Apr 2014

Einstellungen

PSU providing enough voltage?

Based on the diagnostic LEDs I may have a bad PSU, however before I drop $140 on a new one I would like to be sure it is not the logic board.

Diagnostic LEDs

LED #1 is on when the power cord is connected.
LED #2 comes on briefly as the machine appears to try to be starting itself (without the power button pressed) once I connect the power cord.
LED #3 flickers for a time frame smaller than LED #2 right after LED #2 comes on.
LED #4 Does not come on. Likely because of what is going on with #1 and #2 plus I have the display completely removed along with the ram and hard drive.

The process of LEDs #2, #3 flickering is about a second and the machine just loops trying to start. Again without the power button being pressed.

PSU Details

The power supply is an OE Liteon PA-3241-02A1.

There does not appear to be any popped capacitors, the power fuse has continuity, and the diode at the incoming AC power is also good.

Observed Voltages

Below is the voltages I observed on the main power connector when the machine was not trying to start:

Pin #1 Ground
Pin #2 +12v
Pin #3 +1 millavolt
Pin #4 +4v
Pin #5 +.5 millavolts
Pin #6 Ground
Pin #7 Ground
Pin #8 +12v
Pin #9 +12v
Pin #10 +12v
Pin #11 +.5 millavolts
Pin #12 Ground

Below is the voltages I observed on the main power connector when the machine was trying to start:

Pin #1 Ground
Pin #2 +12v
Pin #3 +0 millavolt
Pin #4 +4v
Pin #5 +4 to +7 millavolts
Pin #6 Ground
Pin #7 Ground
Pin #8 +12v
Pin #9 +12v
Pin #10 +12v
Pin #11 +4 to +7 millavolts
Pin #12 Ground

I am hoping some one can confirm outputs I am seeing from the pins.

Diese Frage beantworten Ich habe das gleiche Problem

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1 Antwort

brettkfry @brettkfry Rep: 1 1 · Answer 1 · 2014-04-28T13:07:12-07:00

brettkfry @brettkfry

Rep: 1

1

Veröffentlicht: 28. Apr 2014

Einstellungen

Well based on your issue I don't think it is the power since LED 1 and 2 seem to be working fine. LED 3 also seems to be functioning as usual, but if it goes off could be an indication of bad graphics card. What you could do is try to connect it to an external monitor. I believe if LED 4 is off it is an indicator for a bad inverter or screen (Should be an easy fix).

I wasn't sure if you were saying the monitor was coming on an staying on or going off after trying to boot.

Have you tried to get into recovery mode? It seems as if the system powers on and gets stuck looping trying to boot it would be either a hardware or software issue and if you can run an AHT or get to the recovery menu you might be able to identify what is happening.

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LED 2 will only flash on for a few seconds. It cannot sustain.

LED 4 is off as a result of the display being disconnected. While it was connected the 1,2,3 LEDs did the same thing.

It will not power on to the point of recovery mode.

28. Apr 2014 von Nate

Nate, I will ask anyone I know if they have your model. I am not sure what the exact specs are for the PSU. I tried to search apples website, but no luck =(. I hope I can find the answer. I don't think it is the PSU, but if you find a cheap one on ebay you might try it and test your theory.

29. Apr 2014 von brettkfry

Any luck? Thanks!

10. Mai 2014 von Nate

I will add this comment since there is always someone encountering this problems.

I have the PSU LITEON PA-3241-02A, The voltages are correct as above once the power button is pressed:

Pin 2: 12v

Pin 3: 2.05v

Pin 8,9,10: 12v

the rest are as above, 0 or ground

When the computer is off but power cord plugged in, I get:

Pin 2: 12v

Pin 4: 4V