Two graphic cards not detected by BIOS

[Bross]

Re: Two graphic cards not detected by BIOS

Q223 = 3310HG

This mosfet is connected to both fan connector pins (+ to the source with no impedance, and - to the ground with a little impedance). The drain pin doesn't reach the circuit.

[momaka]

Re: Two graphic cards not detected by BIOS

^ The Drain pin on that MOSFET should be connected to the 12V rail on your PSU, then. Otherwise, check your measurements again, as it doesn't make sense for this MOSFET to be connected to the fan and not to anything else.

[Bross]

Re: Two graphic cards not detected by BIOS

^ The Drain pin on that MOSFET should be connected to the 12V rail on your PSU, then.

I attach a closer shot of the mosfet.

I agree that it should be connected to something more, but measurements are: about 1 ohm between gate and drain, between gate and souce, and no impedance at all between drain and source (in both directions). I guess it's broken anyway, because I see a diode between source and drain in its scheme. So I ordered a new 3310, but it will take a while (it's coming from China).

I'll post more news when I try new things in any of the graphic cards.

[momaka]

Re: Two graphic cards not detected by BIOS

I agree that it should be connected to something more, but measurements are: about 1 ohm between gate and drain, between gate and souce, and no impedance at all between drain and source (in both directions).

That's not really possible.
If you have a low resistance between point A and B and also point B and C, then naturally, there will be a low resistance between A and C too (same stuff as middle school algebra. ) ... unless your meter is somehow getting tricked or I am misunderstanding your description.

I guess it's broken anyway, because I see a diode between source and drain in its scheme.

That's completely normal for a MOSFET. For N-channel FET, you get a diode reading when red multimeter probe is on Source pin and black probe is on Drain. Reverse the probes, and you get nothing (i.e. open-circuit or infinite resistance) - this is of course with the component out of the circuit. In-circuit, low-impedance loads can change those readings completely (typically showing lower-than-normal resistance).

[Bross]

Re: Two graphic cards not detected by BIOS

Ok, I forgot that mosfets are connected to the circuit through their back. Sorry, momaka; but I'm afraid that I can't follow you (I can't see a mosfet as a straight line with A, B and C points).

I finally get the caps out from the red one and measured them: everyone is right. This card is in the same status: fan works, but mob doesn't detect it. PCIe pins cleaned again, and same result.

Measuring one of those capacitors out-circuit (youtube)

I replaced the 3310GH today in the blue one. The old one was clearly faulty (short anywere meassuring it out the circuit), but not only the fan isn't working yet: the mob doesn't detect this card again.

Measuring old & new 3310GH out-circuit (youtube)

I'm afraid that this is more complicated for me that I expected. If anyone has any new idea about something more to check, it will be welcome. If not, I guess I'll quit after some months. Thank you guys in any case

[momaka]

Re: Two graphic cards not detected by BIOS

Well, fan issue aside, since both cards are still not getting detected... likely they just need a reflow/reheating. If you have nothing better to do with these cards and you don't mind giving this a shot, you might get them working again with a bit of luck.

Otherwise, just chuck them in a box and set them outside your house for whoever wants to take them (just make sure they are labeled as "broken / not working" so that some poor soul doesn't carry them all the way home for nothing). Or you can try selling them on eBay for like a dollar/Euro each.