Hello everyone,
I am a newbie and this is my first repair attempt on eVGA GTX 970 that I bought from one guy. He said that his power supply died and took the graphics card with it and smelled smoke from the card too. When I took the card apart, one of the high-side MOSFETs was obviously damaged and there was a short on one of the PCIe connectors.
The situation now is as follows:
- The choke was already damaged when I disassembled the card
- I've desoldered the high-side MOSFET "H" that was damaged, short gone
- I've desoldered the low-side MOSFET above it, just to do some measurements (no shorts). That one seems just fine and I will put it back on the board later
- There is one strange thing about the top driver chip's VCC - all drivers seem to get VCC from PCIe the slot, but all except the top one have resistance around 2 Ohms to the PCIe slot. The top one has around 110 Ohms. Is that normal or there is something bad here?
- I've decided to remove the driver chip due to the resistance above, BUT I've accidentally removed and lost the capacitor, marked as 1 in yellow, that is next to the driver chip. When I measured the pads that the cap was soldered to, the top one is connected to the ground and bottom one to the PCIe slot. So according to the scheme from the NCP81062 documentation, my guess is that it could be C1-C3. (the resistance there is still the same though)
- The question is - I guess it's some filtering cap, would the board work without it?
- I tried measuring the driver chip too, there is nor short on VCC (gives around 62K Ohm VCC to ground pin) and HG is also not short (around 24K Ohm). I've read that it's a good practice to have that driver chip replaced, is there other way how can I tell that the driver is dead or I should just do it no matter what?
Thanks a lot!
I am a newbie and this is my first repair attempt on eVGA GTX 970 that I bought from one guy. He said that his power supply died and took the graphics card with it and smelled smoke from the card too. When I took the card apart, one of the high-side MOSFETs was obviously damaged and there was a short on one of the PCIe connectors.
The situation now is as follows:
- The choke was already damaged when I disassembled the card
- I've desoldered the high-side MOSFET "H" that was damaged, short gone
- I've desoldered the low-side MOSFET above it, just to do some measurements (no shorts). That one seems just fine and I will put it back on the board later
- There is one strange thing about the top driver chip's VCC - all drivers seem to get VCC from PCIe the slot, but all except the top one have resistance around 2 Ohms to the PCIe slot. The top one has around 110 Ohms. Is that normal or there is something bad here?
- I've decided to remove the driver chip due to the resistance above, BUT I've accidentally removed and lost the capacitor, marked as 1 in yellow, that is next to the driver chip. When I measured the pads that the cap was soldered to, the top one is connected to the ground and bottom one to the PCIe slot. So according to the scheme from the NCP81062 documentation, my guess is that it could be C1-C3. (the resistance there is still the same though)
- The question is - I guess it's some filtering cap, would the board work without it?
- I tried measuring the driver chip too, there is nor short on VCC (gives around 62K Ohm VCC to ground pin) and HG is also not short (around 24K Ohm). I've read that it's a good practice to have that driver chip replaced, is there other way how can I tell that the driver is dead or I should just do it no matter what?
Thanks a lot!