Re: Two iMacs 2009 - black screen, backlight OK, GPU OK, four LEDs on - any ideas?
Yeah. One of the first things I did was plugging the LVDS cable to the socked and checkin the connection between the cable lines on the one end of the cable and the socket connectors at the board side where they are soldered.
Repeated that procedure several times unplugging and plugging back the cable.
Once I had the case where I had to replace the LVDS connector but I got the bunch of those cheap ones from Ali.
tom.tom
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Last Activity: 04-22-2025, 12:41 PM
Joined: 02-27-2021
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Re: Two iMacs 2009 - black screen, backlight OK, GPU OK, four LEDs on - any ideas?
One iMac problem solved!
L9000 with infinite resistance was the problem:
...Leave a comment:
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Two iMacs 2009 - black screen, backlight OK, GPU OK, four LEDs on - any ideas?
Hello,
I've recently got two 2009 iMacs (820-2733-A) with the video issue I have never come across before. The symptoms are as described briefly in the topic:[LIST][*]both boot with chime and load the OS (Live Linux from USB),[*]four LEDs are on,[*]the LCDs get the backlight, but no video data (black screen with just the backlight),[*]no video on the external monitor,[*]GPUs are 100% OK,[*]LCDs and LVDS cables are 100% OK.[/LIST]
How do I know the listed components are ok - have working 2009 iMac C2D to exchange the components with.
I suspect motherboards, but two...Last edited by tom.tom; 07-15-2022, 08:45 AM. -
Re: iMac 2011 820-2828 - LED #1 lits for a second then goes off
...of course tried with another CPU - same thingLeave a comment:
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Re: iMac 2011 820-2828 - LED #1 lits for a second then goes off
Hi @piernov,
Had time only today to continue on that. With removed CPU, the LED#1 stays on. Reviewed the CPU socked, removed some strange small stuff from two places, but after putting the CPU back, the LED #1 goes off after a second again.
Any hints where to look at futher?Leave a comment:
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Re: iMac 2011 820-2828 - LED #1 lits for a second then goes off
Resistance of the PP3V3_S5_REG_R line measured on the C7790 pin 1 and the GND gives me around 100ohms - is that OK or shall this be considered as a short?
I'm getting around 3V for a short while on the PP3V3_S5_REG_R line just after connecting the PSU. Does that mean ISL62383 (U7700) is OK and I should look further into PP3V3_S3 and PP3V3_S0 lines or is it too far, because they are powered only after pressing the power button?
If that's the case, the potential problem should be closer to the...Last edited by tom.tom; 02-28-2021, 08:19 AM.Leave a comment:
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Re: iMac 2011 820-2828 - LED #1 lits for a second then goes off
Just to make sure I understand the power rails descendancy - this is described on the page #3 of the schematics, right?
So we have:
1) PP12V_S5 -> PP5V_S3_REG -> PP5V_S0 -> PP1V8_S0_REG
2) -> PP3V3_S5_REG -> PP3V3_S3 -> PP3V3_S3_MINI, PP3V3_S3_ENET
3) -> PP3V3_S0 -> PP1V0_FWPHY, PP3V3_S0_SD
4) -> PP1V5_S3_REG -> PP1V5_S0, PP0V75_S0
Is that correct?
Do I also need to track PP12V_S0?...Last edited by tom.tom; 02-28-2021, 05:38 AM.Leave a comment:
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iMac 2011 820-2828 - LED #1 lits for a second then goes off
Hi all,
Got a 27 2011 iMac that wont boot. In the beginning, when connected to power, the LED #1 was lit and it went off after pressing the power button. I removed the MoBo battery, did SMC reset and now, when plugging the power cable LED #1 lits for a second and then goes off.
Checked with two other different PSUs - same thing.
Checked the MoBo with everything disconnected except PSU - same thing.
Till now have checked PP12V_G3H, PP3V42_G3H in a couple of TPs and adequate voltage is there. Any thoughts what shall I check next?
Edit1: SCM_RESET_L...Last edited by tom.tom; 02-27-2021, 03:40 PM. -
Re: New Members - please post your introductions here
Hello everyone!
I got to this forum looking for the 2011 iMac 820-2828 board documentation and found it!
Thank you already for this possibility, and hopefully I'll get some more help with troubleshooting it.
All the best to you all
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