Mac is recieving power but wont turn on

Ok so this mac is fairly old and probably nearing its retirement age but I still need to use it. The problem being is that it randomly powers off sometimes but more common is it will power off during start-up or not start-up at all. Ive opened the back panel and looked at the LEDs. LED 1 is on whether the mac is on or not (this is correct as its indicating power to the PSU, right?), LED 2 will turn on for a second then will turn black, and LEDs 3 and 4 don't come on at all (though 4 shouldn't come on anyway as that's only on if the macs overheating right?). On the inside the capacitors look good non of them are bulging and since LED 1 is on that means that the issue isn't the PSU or am I wrong? Ive tried turning the MAC on with both the power button and the Internal Power button and the issues repeats itself with both, and some times when the mac turns off there's an audible pop (but it sounds like its coming from the internal speakers but I may be wrong)

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I've repaired about a dozen of these 17" machines. The LED's indicate a failed power supply. Please give us the last three figures of your serial number so we know your exact machine. You can either replace the power supply or send it in to be repaired. Since the caps look good I would recommend the fix. It's pretty easy.

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+ Good answer coming from experience.

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Here's the serial number ranges for the bad caps machines:

Serial Number ranges:

W8435xxxxxx – W8522xxxxxx

QP435xxxxxx – QP522xxxxxx

CK435xxxxxx – CK522xxxxxx

YD435xxxxxx – YD522xxxxxx

Here's how to DIY repair on the power supply:

http://jimwarholic.com/2008/11/apple-ima...

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Thanks, I replaced the power supply with one I had handy from another Mac that had been scrapped. It seems to be working now but given how finicky macs are Im guessing its only a temporary fix, and as you said it was a real easy fix

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Well, I've been working on Apple products since 1979 and I don't fine them finicky at all. Just look in your phone book for the number of PC repair guys and the number of Mac repair guys. Just because a repair is easy, doesn't mean it won't work. I'd just how the power supply you used has the correct voltages for your machine.

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