Imac A1311 late 2009 820-2494A

[ex250]

Hello guys, I have this one with a non-starting failure, on board diagnostic led 1 lights ok, tested other know working power supply to discard, same behavior.

The board is the 820-2494A

the S5 lines read:

PP1V1_S5_REG -> 1.11V

PP3V3_S5_REG -> 3.37V

PP5V_S5_LDO -> 4.98V

PP12V_S5 -> 12.01V

Seems all ok

This ones not, too high readings, maybe the same culprit:

PGOOD_1V1_S5 -> 3.37V (should be 1.1V?)
5VREG_EN -> 3.37 (should be 5V?)

I was thinking that the U7300 could be the problem, but replaced and all is the same.
Any one could point me some direction? Quite lost with these boards.
Thanks!

MOD EDIT Schematic & boardview moved to a new thread - https://www.badcaps.net/forum/troubl...atic-boardview

[ex250]

Re: Imac A1311 late 2009 820-2494A non starting help

No body?

[reformatt]

Re: Imac A1311 late 2009 820-2494A

The 2nd LED on these only comes up when PP3V3_S3 is on, which in turn is enabled from PM_SLP_S4_L. You need to go through the pre-requisites for this signal to be generated from the PCH.

Whilst this is doable, troubleshooting these boards outside of the iMac requires a jig of some nature. Is supplying 12V to the main power input enough from a bench supply? Maybe, but given the age of these things now, I refuse to fix mainboard faults on them.

[ex250]

Re: Imac A1311 late 2009 820-2494A

Sorry for the delay, quite lost on this board. The 12 V supply is ok, tested with 2 different know working power supplies.
It's not quite clear for me how to check PM_SLP_S4_L

[FXD]

Hello all, I am pleased not to be the only one having this "iMac do not start" issue - could someone suggest how to read the schematic file .brd ? I would like to proceed to voltage measurement but not so clear how to do. tks.

[mon2]

.brd = Boardview file.

Suggest to download and apply the following tool by piernov

GitHub - OpenBoardView/OpenBoardView: View .brd files

You can install on Linux or Windows.

You will also need the schematics for this computer which is most likely posted on this section of the forum. Use the search bar to locate.

[FXD]

Thank you for your response. unfortunately whatever the app used I can not open the file. Could someone provide a pdf of motherboard location of control points to be checked ? (S5 line , PP1, PP3 ...) Thank you in advance

[FXD]

Hello, I managed to open the .grb file. By looking for example to PP3V3_S3 check points, I can see many components related, is it sufficient to test only one point or necessary to check all?

[FXD]

Hello again, I try to move froward by myself... If I am right by checking the point shown on the attached picture, I can check all points (example of PP3V3_S3). Is it right ?

[FXD]

Hello, still trying to progress. I could measure as shown on the attached picture. As voltage is ok, I am stuck , how to progress in the investigation ?
now I need your help..