Turns on show apple logo and loading bar then cuts off
hi, I am mainly a phone repair store but usually will take a look at any electronics people bring in. today i was brought a iMac emc 2389 and when i turn it on it shows the apple logo with a loading bar, the fans seem to spin at max rpm and the bar makes it to halfway before the machine turns itself off and then restarts. i tested the psu and it gets 12v on pin 4 and 4.6v on pin 6, so im thinking the psu is still working. the 4 troubleshooting leds all illuminate. so im just looking for some advice on what i can check next. like i said im focused on phone repair so i dont have alot of experience working with macs, i know how to solder and read schematics just not sure where i should even start on this one.