Basic troubleshooting of an old graphics card

[Askic]

Hello to all,

I have an old graphic card, which I tried to troubleshoot. The card is not providing a picture when turn on the PC.
I have checked 12V and 3.3V on the PCIe lanes and they are not shorted, but I have measured 6.5 ohms on the big power supply inductor (measured against the metal ground). Measuring nearby N channel MOSFETS 4C08N and 4C10N, I have found that MOSFET 4C08N has resistance 6.6 ohms between source and drain.
I also found one capacitor that has the same resistance over it.

I'm pretty sure this MOSFET is bad, since it should be kiloohms or even megaohms, like it is the case on the other 4C10N mosfet. I do have a lab power supply unit, but not really good thermal camera to see what is actually heating. Because of the 6 ohms, It is very unlikely to be a shorted capacitor somewhere on the board, most probably it is the mosfet.

I have attached a picture, is there anything else I need to measure or this is sufficient to conclude that the actual culprit is the mosfet?

The card is not worth anything, I'm doing it as a learning experience with GPUs.

Thanks.

[Patrick501]

Hello,
you should desolder the 4C08N and check. A N channel mosfet should be about 0.5V in diode mode.