• Imac 27" A1312 (Main 820-2507-A) No power On

It is currently 14 December 2024, 18:01

Imac 27" A1312 (Main 820-2507-A) No power On

 Forum rules: Click here to view the forum rules

  1. Topic title should contain: the device's manufacturer, full model and the brief description of problem.
  2. Topic message should contain: the PCB marking code (required in case of hardware repairs), an extended description of problem, things you have checked/replaced/measured, your conclusions and the question. If you are not able to find the PCB marking code, please read THIS TOPIC. If you still cannot locate the PCB markings, please upload a clean, both-side photos of the mainboard - it is required to remove any films, modules or brackets possibly covering these markings.
  3. Before posting a new topic please read all topics in TRAININGS subforum and make a preliminary diagnostic based on the content of those trainings.
  4. Uploading of any complete schematics, BIOS / firmware files or any other kind of documentation, or linking to 3rd party websites with such files, is STRICTLY PROHIBITED. You can only upload the small portion of documentation or, link to BIOS file on UNVERIFIED BIOS FILES subforum, which simplifies the diagnostics/repair. You are not allowed to upload more then one complete page of instruction/schematic per single topic. The file you upload must not contain any watermarks, "confidential" markings, links or email addresses and cannot be password-protected.
  5. It is only permitted to describe one faulty device per single topic - you should always open a new topic for each subsequent device.
  6. Requesting of the full schematics, BoardView files, BIOS files or any other kind of documentation is NOT ALLOWED in this subforum. If you need to ask for any of these, you should open a new topic in DOCUMENTATION/BIOS REQUEST subforum.
 This topic is marked as ARCHIVAL. Please only reply if your message contains the solution (Terms and Conditions p. 12.1).

#1 Imac 27" A1312 (Main 820-2507-A) No power On

by robgerr • 11 October 2021, 09:38
Good morning.
I have this imac with the following defect: if I press the power button no sign of life. I have checked the power supply and I am in some 12V output pins. In the connector of the power button I find the 3.3V and drop to 0v when press power button but the machine does not start.Only led001 on but no other after press power button . I tried to do a CMOS reset by removing the backup battery for some time. I tried to reprogram the bios but nothing. I no found traces of oxidation or visually burnt components. The only thing I noticed was that the R5158 resistor was missing and I simply jumpered the two pads as it is a 0hm resistor.
In the L7920 i have 1,11V
C7670 i have 5V

Re: Imac 27" A1312 (Main 820-2507-A) No power On

by Google Adsense [BOT] • 11 October 2021, 09:38

#2 Re: Imac 27" A1312 (Main 820-2507-A) No power On

by ado • 11 October 2021, 13:14
Witam , czy sygnał PM_SLP_S4_L wystawiany przez MCP ma wartość 3,3v po wciśnięciu przycisku zasilania?

#3 Re: Imac 27" A1312 (Main 820-2507-A) No power On

by robgerr • 11 October 2021, 15:48
Hi Ado
Measured PM_SLP_S4_L on the R7053, after press power button voltage up to 3,37V

#4 Re: Imac 27" A1312 (Main 820-2507-A) No power On

by ado • 11 October 2021, 16:04
ALL_SYS_PWRGD ma tez wartość 3,3v?

#5 Re: Imac 27" A1312 (Main 820-2507-A) No power On

by robgerr • 11 October 2021, 16:19
ALL_SYS_PWRGD measured on the R7098 pin 1, 0V
ckecked PP5V_S3_REG and is absent.
Measured U7300, pin 11 12V and after press power button enabler (pin 1 ) voltage up to 3,70V but on the L7320 Coil no voltage.
Checked L7320 resistance to ground 1Kohm

#6 Re: Imac 27" A1312 (Main 820-2507-A) No power On

by ado • 11 October 2021, 18:05
U7300 możesz podstawić? Szukanie PP5V_S3 to właściwa droga bo musi ono się pojawić jako pierwsza linia zasalania S3.

#7 Re: Imac 27" A1312 (Main 820-2507-A) No power On

by robgerr • 1 December 2021, 15:38
Hi ado, replaced U7300 but same problem, no voltage on the L7320 Coil

Re: Imac 27" A1312 (Main 820-2507-A) No power On

by Google Adsense [BOT] • 1 December 2021, 15:38
 This topic is marked as ARCHIVAL. Please only reply if your message contains the solution (Terms and Conditions p. 12.1).
Similar Topics
  Macbook A1708 Main 820-00840A no power on
  Imac A2116, płyta: 820-01237-A zwarty kondensator na linii 5v  [SOLVED]
Macbook A2485 ( 820-02100-A) no power , stuck at 5V
[BIOS DUMP] LG GRAM 17Z95N Platforma: 1XZ95N MAIN B/D
  Acer TravelMate P256 Main LA-B162P It does not turn on  [SOLVED]
[BIOS DUMP REQUEST] ASUS ZenBook Flip UX463FL (UX334FL MAIN BOARD REV. 2.0)

Who is online

Users browsing this forum: No registered users and 0 guests

_______________________________
All rights reserved. Unauthorised copying of this website's content or any of its part is strictly forbidden.
Any trademarks, brand names, products or services published on this website belong to their legal owners, are copyrighted and used for information purposes only.