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)
Is this a good question?