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Thought it was my Logic Board... but not. What now?


I came home from work (where my MBP was working just fine), got home and started it up (not from sleep), but got no startup chime, sleep LED was on and the optical drive was running, but nothing else. I did some research and found out about the Nvidia chip problems and the logic board problems.

So I bought a brand new LB, which has the revised 8600 GT chip, (and according to the seller, was tested in a mac before being sold) and installed it today. I followed all the directions to the "T" from this website (THANK HEAVENS you are here) but when I got everything back together and attempted the startup. It exhibits the same symtoms.

It COULD be another bad board, but I also remember vaguely reading something here where someone mentioned it could be a bad left I/O board.

Well, I am not sure. The power adapter plugs in and it lights up green when the battery is charged, but is that amber color when it is not. so - I know it is charging the battery. Could it still be a bad left i/o board?

Thanks a million!


MBP 2.5 Ghz. 17inch (early 2008) A1621


OSX 10.5

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One more thing to add - after being "on" for an hour now, the area along the F-keys is warm (where it usually is when it was working fine before). I am not sure what is happening. I don't hear any fans (yet). I'll update this in an hour or so.


It's been on for over three hours - still warm (almost hot to the touch where the F keys are. No fans. Hope to get an answer about the i/o board possibility soon. I'm in the middle of two BIG projects now and really need this to be working!


One more thing: A few months ago - I remember it now. There was a slight electrical burning smell - no smoke or anything - coming from the left hand side of the computer - near where the power goes in. I don't know why I didn't think of that before.


OK - this is disheartening.

I've replaced my Logic Board and the left i/o board. It is STILL exhibiting the same symptoms. I followed the instructions to the T, but it is still exhibiting the same symptoms. I just don't know enough about this to really be able to troubleshoot beyond what I've already done. No startup chime. solid LED sleep light. optical drive powers up, but pretty much that is it.

if I had bad fans, would it still pass the POST? For all I know this could be a bad wire or something - I just don't know what to do beyond this point. I cannot track and success or failures because there has been no change in the symptoms from replacing the LB or the i/o board. I am really stumped.



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The warmth coming from the F-Keys is because your fans aren't working properly. Please shut the machine off. Sounds like u have a fried I/O Board. I don't think you need a logic board. Try replacing the left I/O board. Ask the seller of the Logic Board you purchased if he's willing to cut u a deal and sell you the left I/O Board.

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THANKS!!!! I was pretty sure that was what the problem was. But would a fried i/o board give me the non-chime/blank screen and solid led sleep light symptoms?

I might just keep the old lb in case - seems like nearly everyone who has these has had more than one go out on them. $75 more for the i/o board isn't going to hurt me.


When u hear a chime, that means that your machine has succesfully tested and passed POST tests. If u have faulty hardware, it can definitely affect bootup process.


P.O.S.T* meaning Power On Self Tests.


Thanks!! You've helped so much!!

You know, In the year or so I've had this MBP, I don't think I EVER heard my fans come on. Could the left i/o board be responsible for that, even if it seemed to be working properly for the power, audio and usb? There are two fans, does it control both of those? Sorry to ask all these questions, but this is helping me so much.


Well, download SMC fan Control, its free, and it's a great utility that u can monitor right from ur task bar, and you can see CPU temp. Fan Speeds and increase or decrease fan speeds. Most Mac fans are almost silent when functioning properly, so download that utility and see if the fans are working.


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I am having exactly the same issue - did you ever get it resolved? One difference with mine: After various troubleshooting (removing ram, starting with no battery, etc.) I left it for 2 days, then miraculously it booted. However, then I put it to sleep and now have the same issue again.

Any tips on what your issue ended up being?



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@Matt Gorbet, this question is 3 years old and not visited to often. Your question is showing up as an answer and may get lost with ever getting answered. I suggest that you ask your own question and give as much detail as possible.


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Hi Turn laptop upside down and wrap in towel or bed duvet while switched on for about 30mins then switch off and let cool down still upside down for again approx 30mins, Switch on again and if it works it is a solder problem with your graphics chip on the motherboard it will work for a while like this but you will really need to get the solder reflowed on your motherboard especially the graphics chip.

Let me know what happens.

Yours Sincerely Jeremy

PS Do not sell like this as unfair to person who buys when you know about this fault. Disabled former Forman Electrician latest qualification HNC/D in computing and information technologies.

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jerrywickham sera éternellement reconnaissant.
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