Re: Broken Pentium 2 Motherboard
Okay, transistor 6... the 1802... the only data sheet that I think matches what we have is 2SD1802. It's an NPN BJT, not a MOSFET. Regardless, it just doesn't make sense to me why there is 0V on both the tab (which is the Collector, or position A as we called it) and the leg (the Emitter, or position B). A larger transistor like this is always used for handling power to major components, and in such a configuration, it's leg wouldn't be connected to ground.
Let me think about this one for a little bit till tomorrow. Meanwhile, can you check if the tab is connected to any voltage rail on the PSU? To do this, disconnect and remove the power supply, and see if any of the pins in the ATX connector show zero Ohms resistance with the tab on the 1802 transistor. Also see if the middle pin of the fan hearder right next to the 1802 BJT shows low resistance to the tab.
At this point, I'm trying to determine what that transistor does. The way it has zero volts just doesn't seem right. You did measure the voltages on that transistor with the computer turned on, right?
Okay, transistor 6... the 1802... the only data sheet that I think matches what we have is 2SD1802. It's an NPN BJT, not a MOSFET. Regardless, it just doesn't make sense to me why there is 0V on both the tab (which is the Collector, or position A as we called it) and the leg (the Emitter, or position B). A larger transistor like this is always used for handling power to major components, and in such a configuration, it's leg wouldn't be connected to ground.
Let me think about this one for a little bit till tomorrow. Meanwhile, can you check if the tab is connected to any voltage rail on the PSU? To do this, disconnect and remove the power supply, and see if any of the pins in the ATX connector show zero Ohms resistance with the tab on the 1802 transistor. Also see if the middle pin of the fan hearder right next to the 1802 BJT shows low resistance to the tab.
At this point, I'm trying to determine what that transistor does. The way it has zero volts just doesn't seem right. You did measure the voltages on that transistor with the computer turned on, right?
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