Wire routing of video inverter causing jerky video?

Thanks to iFixit's replacement guide, I was able to remove and repair the bulging capacitors on my logic board that prevented boot up of my iMac. In the process, I may have caused another problem - jerky video while viewing YouTube (or any other video file). Let's start at the beginning: The iMac stopped booting up, no B/U chime, no fan, no video. I removed the logic board and repaired the caps. Reassembled. Booted with 3 LEDs but no backlight. Desktop behavior seemed fine using a flashlight. Initial boot problem fixed. Researched backlighting problem and found out about the inverter. Took the inverter out and found that the subsequent backlight problem was due to the inverter cable coming unseated during the initial (bootup) repair. Re-installed the original inverter and now the computer boots fine and has backlighting. The only problem now is jerky, frozen, video (as if you had a very slow Internet connection). The audio to the videos are fine. The audio does not lag at all. I'm wondering if somehow I could have pinched or mis-routed an inverter wire during reassembly, or do I need to order an inverter. I am traveling and want to have a plan when I get back home. Thanks very much!

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Since the mac is old, it may just not be powerful enough to play YT. Have you tried running ASD(apple support diagnostics) and seeing if you get any sensor errors or other messages?

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I have not done ASD and will do so, thanks. It doesn't matter what video is playing (a file on the HDD or web) the problem occurs. Didn't do that before it stopped booting (2 months ago).

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That probably isn't a problem with backlight inverter, more likely the GPU. If it also happens with external monitor you can be sure that it is not the backlight inverter or LCD.

Run ASD and also this: http://www.geeks3d.com/gputest/

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Completely ignorant until now of what the inverter does. Thanks for that info AND the GPU test link. I neglected to say in the original post that I only changed the five bulging caps and not all of them. Knowing that the GPU is on the logic board, that (as Mayer has suggested) is probably my issue.

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The main issue with this model was bad capacitors (cans), There are about twenty-four of them on the logic board. Take a look at them and see if any are swollen and/or leaking, or have bulging tops.

Update

Jim Warholic is the definitive authority on this issue. I'd read through what he has to say on it here:

http://jimwarholic.com/2008/07/how-to-re...

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As I 'fessed up earlier to Ethan, I only changed the 5 visually bulging caps on my logic board and then reinstalled it. I have the entire J West Sales cap kit but hoped if the caps weren't visually swollen they'd be alright, wanting to avoid the gnarly cap replacement torture. Since I now know the GPU is on the logic board, it might be that some good-looking caps may be bad. I see many small cans that appear like eraser-sized capacitors. Could these be suspect as well or just the electrolytics?

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i think because more than 5 years, your imac connection and soldered are cracked, weak,or loose.

if you have much time , you can disassemble the logic board clean it up with 99% alcohol or thinner. it's fine as long as not to clean the plastic materials.

take the heatsinks out and clean them

change the heatsink paste, better give the logic board heat before. about 100c to 150 c (or you can see the capacitors max degree can hold and set it 20% below that) for about 3-5 minutes max. you can look up youtube how to bake logic board. cool it down then go on change the paste.

if you have hot blower, you can focusing the heat at 135c on gpu and cpu for about 2-3 min ( you can also search for references for reflow gpu temperature profile for more details)

put them back together and hope it work.

May best luck with you..

note :

take it with your own risk

careful with it by doing it slowly. take your time

read the references before doing it make your strategy to do the efficient way and not forgetting something.. if it is hard for you to do that then don't waste your time.

i gave you this advise because of my experiences with some mac or pc no matter model.

sometime it did not work. but my worked score still higher...

cheers

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Thanks Fabien GamingT. What you suggest with reflowing the processors is probably best left to braver folks like yourself. I would be skeered of doing something that extreme although I've seen brave souls do this on YT. I appreciate your suggestions though and will put this at the "last resort" part of the list. :-)

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