iMac in reboot loop black screen and chime, keyboard not recognize.

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iMac Intel 24" EMC 2134 and 2211

Model A1225 / Mid 2007 and Early 2008 / 2.4, 2.8, or 3.06 GHz Core 2 Duo processor

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Jim @jimks

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发帖于: 2020年5月5日

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iMac in reboot loop black screen and chime, keyboard not recognize.

Hi,

First of all, I have to thanks the all community on Ifixit. So many Topics helped me so much. Now I guess it is my time to ask you guys some help, please.

My iMac (VM831NV60KM) suddenly stopped working while I was using it.

Now, it’s rebooting in loop with black light, chime, fan but no keyboard recognized .

LED Diagnostic showed 4 LED lights are working. all ON, I mean.

I’m wondering if the problem can be the CPU, Logic Board, or power supply? CPU and power supply should work if the all 4 LED lights are on, isn’t? So it’s the Logic Board?

Thanks for your help.

cheers

Jim

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Hi @mayer any chance to have your expertise on that please ? I have read many many of your expertises and you’ve always been meticulous and pro. Some articles close to my issue have been checked for you, so I am wondering if you can help me a bit please ?

thank you jim

由 Jim 完成的 2020年5月6日

What type of keyboard are you using?

由 mayer 完成的 2020年5月6日

Hi @mayer thanks for replying.

I use a USB apple one. I plugged a USB computer mouse, I have seen its light. but couldn't see any lights from the keyboard, I tried with a another keyboard but not a apple one, no light as well.

so I did all the commands like, ALT, D, Cmd + R, alt + Cmd + P + R, obviously it didnt worked.

I tried to boot the imac with a usb key. everything was the same. It is just rebooting in loop.

由 Jim 完成的 2020年5月6日

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Hi @mayer any chance to have your expertise on that please ? I have read many many of your expertises and you’ve always been meticulous and pro. Some articles close to my issue have been checked for you, so I am wondering if you can help me a bit please ?

thank you jim — Jim
Hi @mayer thanks for replying.

I use a USB apple one. I plugged a USB computer mouse, I have seen its light. but couldn't see any lights from the keyboard, I tried with a another keyboard but not a apple one, no light as well.

so I did all the commands like, ALT, D, Cmd + R, alt + Cmd + P + R, obviously it didnt worked.

I tried to boot the imac with a usb key. everything was the same. It is just rebooting in loop. — Jim

score 1 · Answer 1 · 2020-05-07T08:49:14-07:00

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mayer @mayer

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MacHale Enterprises

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发帖于: 2020年5月7日

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Apple iMac 24-Inch "Core 2 Duo" 3.06 (Early 2008) Specs

Identifiers: Early 2008 - MB398LL/A - iMac8,1 - A1225 - 2211

This is a very unusual case.

I would first try the keyboard in all the USB slots.

I would be inclined to go for the power supply first. These things can partially fail and supply power to things and not others. Pull it and look for bad capacitors (cans). This was a major issue about the time your machine was produced. Bad caps may have swollen tops and/or show leakage.

UPDATE 5/26/20

If I remember correctly, this machine came with system installation DVDs. Please insert the install DVD, hold down the C key and boot from it and tell us your results.

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We Computing @wecomputing 声誉积分: 67 3 · Answer 2 · 2020-05-05T13:40:44-07:00

We Computing @wecomputing

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hi , i doubt it is the CPU , they are rare to go faulty but logic board -Yes if not light at all after 5 min ,

all the best

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Hi, thanks !! Well, I am happy to buy a Logic Board and replace it but I'd like to be quite sure. Yep back light then chime then it reboots. 4 led lights are On. Any more advices or things to check ?

由 Jim 完成的 2020年5月5日

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Jim @jimks 声誉积分: 1 1 · Answer 3 · 2020-05-08T06:51:35-07:00

Jim @jimks

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Hi @mayer

I checked all usb nothing worked.

i checked the power supply but I have no idea of what is good or wrong so here some pictures

one place looks darker… like I said I don’t know if it’s normal or not.

then when I remove the thin cable, the “thermal paste” ? Had a crack but still in place.

Aslo I just remember, before the imac crashed, days before I had the screen turning black for few seconds or even minutes…while i was working with.

thanks @mayer

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I'm not seeing anything unusual on the power supply. Next carefully examine the logic board looking for a burned component.

由 mayer 完成的 2020年5月8日

I will check then. do you think there will be any issue with the little thermal paste's crack ?

由 Jim 完成的 2020年5月8日

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Jim @jimks 声誉积分: 1 1 · Answer 4 · 2020-05-08T11:32:39-07:00

Jim @jimks

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The logic board is even more fine

i mean nothing looking bad noticeable.

So yes like I said. Before the iMac crashed. I had the screen turning black for no reason. Sometime secs sometime minutes. I don’t know if that can help

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@mayer or anyone, any recommendations ? thanks

have a great day

jim

由 Jim 完成的 2020年5月11日

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