When i power on i can hear the chime and then I can see noise on the black screen right before the white screen that has the loading icon on it. They are tiny multicolored specks that from afar look like vertical lines.

After this happens then the machine has a hard time booting. Sometimes it boots sometimes it doesn't. When I boot in safe mode it works every time and then occasionally I will see the noise while i am already logged on. When i boot in normal mode it will sometimes go to a black screen at the beginning of the boot and then the fans turn on at full blast "vacuum cleaner mode" i believe is what some of you guys call it.

I have searched everywhere for a solution and to pin point the problem. I have inspected the capacitors on the Logic Board and they are fine, not bulging or leaking. i have inspected the caps on the power supply and they are fine except that I missed the ones under the wiring harness. I will check on those asap.

Whenever I see someone with the same symptoms they almost always get the same response: Bad caps, bad power supply, bad logic board. I think it is the logic board but my question is: If in fact it is the logic board causing the problems, would the GPU be the cause of the problem? Has anyone tried to fix/ reflow these graphics chips?

I have seen it done on iBooks and laptops so I am wondering if anyone has tried it on iMacs. I have fixed many Xbox 360's this way and i have all the tools needed, but before I try it i want to make sure that a bad GPU would cause these symptoms and not some other part of the logic board. I would hate to buy a complete new logic board when all this one needs is a quick reflow.

⟐ Commented September 17, 2014 at 10:31 MST

Thank you

⟐ Answer accepted September 11, 2021 at 6:47 MST

thanks very much.

⟐ Answered February 01, 2015 at 15:29 MST

⟐ Answered December 14, 2009 at 9:54 MST

⟐ Answer accepted November 04, 2018 at 11:52 MST

I want to use GarageBand on my Windows PC as my friends have told me it’s way better and doesn't crash at all.

Any suggestions?

⟐ Commented June 30, 2022 at 3:20 MST

Is it possible to upgrade the 1.8 logic board with the 2.0 logic board and upgrade to the 2.0 power supply in an iMac that originally was a 1.8 ghz?

⟐ Answered November 29, 2012 at 14:04 MST

⟐ Answer accepted November 09, 2015 at 10:17 MST

is there any chance to find a new one ?

the old one is dead - it gets hot after the iMac is switched on - the iMac wont start, some times it shows the red led - sometimes it switches immediately off.

after that, i startet searching on the logic board and burned my finger tip on this part

⟐ Answer accepted November 15, 2011 at 0:45 MST

It was having general instability problems so I tried putting a clean reinstall of the OS, but the process failed, three times in a row. So I ran the AHT disk which came with the machine, and it quickly failed the short test with the following error code:

2I2C/1/1:0x00000092

Sounds like it could be related to the I2C bus to me. However, the I2C system is mainly diagnostic and reporting in nature. It reports actual voltage levels on the ram cards and PCI slots, stuff like that. So possibly, this error may not be the real problem.

I took the machine in to an Apple store and one of the techs noticed and showed me there was a bulging capacitor. Since they can only replace the whole board and send the old one back for remanufacturing (expensive), I wanted to try to fix it myself.

After reading about the capacitor/power supply problems I got a new power supply and worked on identifying the capacitor and finding its specks. I learned that beyond the capacitive value, voltage, and temperature ratings; that there are three related charateristics which seem to be critical to the power filtering role these capacitors play in this machine. (impedance or Z)^2 = (equivalent resistance or ESR)^2 + (capacitive reactance or X)^2 If you know two of them you can compute the third. Typically ESR is small and Z ~= X.

So why is this relevant? Well, the original capacitors are Chemi-Con KZJ Ultra Low impedance line with a Z = 12.5 m Ohms @ 100 kHz, unfortunately, this line was discontinued. Chemi-Con current offerings have impedances which range from 22 m Ohm to 49 m Ohm. Nowhere near the original spec. Worse, Digi-Key and Mouser don't carry the better lines, not even in a quantity of one! So I ordered the best available. When it arrived, I removed the bulging capacitor and soldered the new one into place. I also swapped out the power supply. Restarted the machine and... exactly the same problem as before. It still doesn't pass AHT, same error message.

So, does anyone on here have some advice on what I should try next?

Sorry about the long explanation, but hopefully it explains why I'm finding the whole thing puzzling. Why does Chemi-Con no longer manufacture capacitors with such low impedance any more? Why doesn't DigiKey carry what they do offer?

⟐ Answered July 26, 2015 at 5:06 MST

How can I tell if it is worth getting the parts to get it running. Is there a way to test it somehow to see if the screen/works works or if the logic board is good? I looked it up online and all the parts would run me about $600 +/-. Would LOVE to fix it up, but don't want to spend the cash to rebuild it if it turns out be around the same price to buy a new one.

Thanks for any help in advance.

Dzyner

Thanks for your answers. Mactech plus: The logic board looks OK, I am pretty proficient in repair on Macs, replacing HDs, keyboards, etc, but DO NOT know anything regarding the logic board. I looked at it and it seems OK. No seepage or anything like that from anything.

Is there a way to test the circuits or to see if the display will work without buying all the stuff first?

Thanks again for your opinions.

⟐ Answer accepted November 27, 2013 at 20:06 MST

⟐ Answer accepted November 01, 2016 at 11:53 MST

⟐ Commented April 26, 2015 at 15:26 MST

Is it a bad power unit?

Please help!

⟐ Answer accepted September 08, 2013 at 11:54 MST

Hey guys, sorry it took so ling to answer back. I finally got a hold of a 10.5 dvd. No issues with date/time of fan spinning up like crazy. So that's what my problem was the whole time was wrong OS. Thanks again for the help :)

⟐ Answer accepted April 02, 2013 at 12:20 MST

⟐ Answer accepted May 13, 2012 at 19:09 MST

Any tips ?

Thank you. I guess I'l have to live with it then.

A 2 inches blue cloud ain't that bad after all.

It's not as bad as the time my daughter "painted" my 22 inches screen with a magnet...

Had to buy a machine to take care of this one

⟐ Answer accepted March 08, 2010 at 7:30 MST

⟐ Answered February 09, 2010 at 9:52 MST

⟐ Commented October 08, 2020 at 21:15 MST

So far, here is what I tried:

• PRAM reset (~3/24/19)
• SMC reset (4/5/19)

I checked the CMOS battery (Panasonic CR2032) and it reads 3.07V, so it was likely replaced before I got it or it’s an original cell that still works. I can usually clear it up by adjusting the volume and that solves the issue, but it may eventually come back - even with an SMC reset performed.

Should it come back, what should I look for? I have a QP538 machine, so I’m firmly out of capacitor plague territory. I don’t think it’s the caps because of how out of the range mine is. The software was a recent install as well, since I had to start fresh due to how I got the machine; I also wanted Classic support, so it required a 10.4 downgrade.

⟐ Answer accepted April 05, 2019 at 22:44 MST