Recent content by kodaf56

Once again it was just one pin on 81161 that caused this. It wasn't soldered properly, because I really should use solder in paste or at least clean the old solder and not just reflow the solder that was there. I'm still learning hot air soldering. But anyway after making sure that every pin is...

I’ve been using 858D hot air station.

From what I found, 81161 is decreasing resistance of this resistor (without it resistance is 10K, just like after desoldering this resistor from the board). But on this phase even with a 81161 from the other phase it still has that 8.7K resistance.

I did that and those resistances are the same, 10K for each.

Yes, it’s the same on every phase.

There is continuity to the high side gate pin on the mosfet and 1.6 ohms to the high side gate drive.

It is actually, to every output choke. Same for the other resistors. There’s continuity there. And yes exactly. On the other phases there is 7.7K -7.8K but on the suspect phase there is 8.7K.

It’s 1.8 ohms. There might be something in between actually when I think about it now, don’t know what though.

Not exactly, resistance on the ground leg is near zero. But something happens when measuring through this resistor and resistance is higher than the corresponding resistors on the other phases. But resistor itself is good.

What seems to be confirming that is that on the faulty phase there is a higher (about 1K higher) Gate to Ground resistance on my card. From what I can see this resistance is mostly depending on a resistor between high side gate driver output and ground (R510 on the faulty phase). Resistor itself...

I think that it might be just a PCB that goes bad after waranty time due to insufficient cooling of VRM. I literally tried swapping everything on this phase and result is always the same. I guess this card just can’t be fixed.

Yes, I'm using hot air.

So it was just a poorly soldered pin that caused that. I did manage to run it after fixing that and replacing the inductor and also mosfet and voltages and resistances on the faulty phase were the same as the other phases. But it died again anyway, even faster within few seconds of load. This...

Well, that was exciting. So I swapped NCP81161 and the bootstrap cap and after that forward direction resistance was 13.5K so close enough to that 14K of a good phase. Then I connected my multimeter probes to measure bootstrap pin to ground voltage and I turned on the computer. Multimeter showed...

It might be possible that the previous bootstrap capacitor was indeed faulty and did something to the changed NCP81161 on the faulty phase. Therefore I'm getting those weird values. Just guessing. I can swap the NCP81161 again, but I don't know whether it's even worth trying that.