Screen flickering on and off

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iMac Intel 24" EMC 2267

Model A1225 / Early 2009 / 2.66, 2.93, or 3.06 GHz Core 2 Duo processor

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Jesse @jesse84941

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发帖于: 2013年8月15日

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Screen flickering on and off

I have an Early 2009 iMac 24 Aluminum (2.93GHz) and had it in a box for a few months, then started using it again after moving into a new house. When I powered it on, after booting up, the screen starting going black then back on, then black, then back on. Quick flashed of the screen turning off.

I randomly decided to lower the brightness down to 40% and it has not been flickering anymore. Any thoughts what the flickering is from? Surge protector? After market RAM that was installed recently? Graphics card?

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originalmachead @originalmachead

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发帖于: 2013年8月16日

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Sounds like a graphics or controller issue. Connect to an external monitor. If the behavior is there it's part of the VGU/VGC, if it's gone it's a component in your internal display chain.

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Can I explore this more? I had the screen (+ other parts) off mine to replace a hard drive & to fit an SSD in the SuperDrive slot for a FusionDrive. This works well but months later I got the flicker/black outs. Sometimes it flickers to dim but usually it cycles on then black every 5 seconds or so. The external monitor is unaffected. If I gently flick the screen it comes back on until it happens again. I have an app called iStat for temps etc. & thought the issue was high temp & if I set the fan from default (which is silent) to medium (which is faster) the problem goes away. However, I now think it is the slight vibration of the fan on medium that keeps a flaky contact good. I read that soldering wires onto the screen can make connections good.

Any further thoughts would be appreciated. As everything (apart from the screen) works whilst its black, what components are involved? Can VGU/VGC intermittently fail?

Fan set to default/slow = flicker/black cycle, fan set to medium = no problem??

由 MervynG 完成的 2017年12月31日

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Can I explore this more? I had the screen (+ other parts) off mine to replace a hard drive & to fit an SSD in the SuperDrive slot for a FusionDrive. This works well but months later I got the flicker/black outs. Sometimes it flickers to dim but usually it cycles on then black every 5 seconds or so. The external monitor is unaffected. If I gently flick the screen it comes back on until it happens again. I have an app called iStat for temps etc. & thought the issue was high temp & if I set the fan from default (which is silent) to medium (which is faster) the problem goes away. However, I now think it is the slight vibration of the fan on medium that keeps a flaky contact good. I read that soldering wires onto the screen can make connections good.

Any further thoughts would be appreciated. As everything (apart from the screen) works whilst its black, what components are involved? Can VGU/VGC intermittently fail?

Fan set to default/slow = flicker/black cycle, fan set to medium = no problem?? — MervynG

kenneth krabat @kennethkrabat 声誉积分: 49 4 2 · Answer 1 · 2019-07-19T14:23:48-07:00

kenneth krabat @kennethkrabat

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发帖于: 2019年7月19日

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My “solution” is different: If the iMac is cold, the screen is black. No problems on the attached monitor, so I set a movie going in VLC and soon the iMac is warm enough to reduce the flickering.

re the above answer: “If the behavior is there it's part of the VGU/VGC, if it's gone it's a component in your internal display chain.” Does that mean that if there is no problem with the external, its #”a component in your internal display chain”? BUT what does that mean?

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I think that heat or vibration makes good a flaky contact. Either a plug from screen to motherboard or (as I read elsewhere) a break where the wire(s) attach the screen (someone showed how to re-solder then but I can’t find the article mow). A diagram or description of the various parts in this chain would be very useful if someone could provide one.

由 MervynG 完成的 2019年7月19日

Yes. That diagram would be most useful!

由 kenneth krabat 完成的 2020年1月4日

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