picked up a dead iMac 2010 27" and revived it but have issues

[stevescivic]

Hello folks, I was fortunately enough to snag up a used 2010 27" iMac i3 w/ 12GB of RAM for practically nothing. Seller said it just died one day. I tore into it and saw the power supply board was pooched (bulged cap) and while I tried to repair the power supply that I was unable to revive it. I ended up finding a used power supply locally and fixed it and found it it has a bad hard drive too. I managed to boot the computer with an external SSD and found out that:

1. According to Mac Fan Control that the PSU Primary temps were getting crazy hot - like 80-90C! The top left corner felt crazy hot to the touch. Comparing it to my 2010 fully decked out 27" iMac i7 that my daily driver mac NEVER has a PSU primary temp of more than 60-72C at most doing typical email/websurfing and other activities. I even used mac fan control to turn the fans to max power and I can feel a nice breeze coming out from the top of the computer and the air is HOT. That is insanely warm temps for a computer that just booted up and was on for maybe 10 minutes doing basic things like signing into iCloud.

2. The display panel is showing these very fine vertical lines scrolling up the screen and the edges of the LCD seem "off". It is akin to someone breaking an LCD display and there is "bleeding" on the edges of the screen. The computer displays fine but clearly there is something amiss with either the display panel or the GPU.

The computer when I took it apart was absolutely filthy inside. I can see how the original PSU and HDD burned up... I don't think the fans were able to move ANY air in the unit given how must dust was blocking the insides.

Upon a deep cleaning and replacement of the power supply unit, I have confirmed that all 3 fans are running smoothly before I replaced the screen back onto the unit.

Would a bad logic board cause the amps to shoot through the roof and cause the power supply to get hot or could the power supply be defective?

Thanks,

 

[Nguyen Duc Hieu]

Your description is great, but I would love to have some photos posted here.

 

[stevescivic]

I'm not sure if I can capture the lines on the screen very well. They're really fine and you'd had to be looking for them.

That being said, I'll try to get some pics up later today.

Regarding the PSU temp issue. Yes it does run quite hot when the screen is cranked to max brightness but I found that the moment I dial the brightness down just a few notches that the temps DROP significantly down to 70C or even lower (hovering around 68C). I left it on all night streaming youtube videos at slightly above 3/4 max brightness and this morning it was 68C.

I've got my i7 2010 iMac that I'm typing on set to max brightness and so far the PUS temp hasn't broken past 65C.

Would a bad inverter board:
1. Cause this spike in current draw that is causing the PS to work overtime? Remember this iMac was BADLY neglected on the insides and the original PSU had a bulged cap which is a sign of aging that was likely accelerated by the intense heat.
2. be the cause the near perfectly spaced lines to appear or is that more of a faulty display/GPU issue?

I probably can get my hands on a used inverter board but I'd prefer to not have to buy extra parts that I don't need to fix this.

Thanks and I will try to post pics later.

 

[Nguyen Duc Hieu]

2. The display panel is showing these very fine vertical lines scrolling up the screen and the edges of the LCD seem "off". It is akin to someone breaking an LCD display and there is "bleeding" on the edges of the screen. The computer displays fine but clearly there is something amiss with either the display panel or the GPU.

Would a bad logic board cause the amps to shoot through the roof and cause the power supply to get hot or could the power supply be defective?

Thanks,

The iMac had been probably used as a monitor with maximum brightness for a long time enough for the LED to heat up and fail.
Hot LED would cause some thin cracks or burning strip on the glass (the inner glass of the LCD panel, not the protective glass on the external.) One or two LEDs on the LED strip might already be dead, thus "the edges of the LCD seem "off" => a little dark on the edge.
Of course the LCD converter board, after a long time being stressed to supply max current to light up the LED, might got used to it, therefore even when you change another PSU, it still draw current from the PSU, causing it to heat up fast.
Just my two cents of ideas, after watching quite several TVs with a half dark screen.