Reply 40 of 77, by Doornkaat
Hi! just quickly on the measuring: You can try to measure shorts with the multimeter first. The four pins in the middle are ground, all of the other pins should have very high resistance against ground. Pull the connectors off and measure, if one measures low there's a short on the mainboard, often a bad capacitor.
To measure voltages safely while the system is turned on you can jam a bent up paperclip into the AT power connector next to a cable after plugging it into the mainboard and use any ground as reference. Just make sure it makes contact inside the connector.
For help measuring the transistor I'd need a better pic or simply the text on the transistor so I can look up the datasheet.
Measuring on the socket is a little trickier but basically you flip the board over and probe the socket pins sticking through the PCB. If you don't trust the steadiness of your hand the transistor measurement should already be enough to determine wether the CPU is getting power. So we'll leave that fun for later if the other measurements are inconclusive. 😉