I'll take a look at mine once it's not in use anymore. Currently it's in a PC that I'm running scandisk on the drive of, ETA: about 10 hours. 😀

But in general, "Q" in electronics notation refers to a transistor. Could be a BJT or FET.

Silly me, I realized that I have a GF2GTS in that running system. The 3Ti was in a box.

I pulled it out and did some measurements on Q200. Keep in mind that this was done in-circuit, but I'm reasonably confident that it's a NPN transistor with the polarity as annotated on the picture below.

No idea however what the specs of that transistor might be. It doesn't look like a high power part.
The marking on it is "1P", no clue how to decode that.

It may be this: https://www.mouser.com/datasheet/2/916/PMBT2222A-2885992.pdf
a SOT-23 version of the very common 2N2222.
The pinout is different from that datasheet, E and B are switched. I know they were manufactured with various pinouts and this may be a variant.

stamasd wrote on 2024-10-12, 11:49:

It may be this: https://www.mouser.com/datasheet/2/916/PMBT2222A-2885992.pdf
a SOT-23 version of the very common 2N2222.
The pinout is different from that datasheet, E and B are switched. I know they were manufactured with various pinouts and this may be a variant.

stamasd thank you so much for helping me out. I have some more info. I noticed that one of the AGP traces is broken. I'm a little concerned that the trace may have been blown from a short but maybe that short came from the motherboard.

I followed the connectivity of that connection, and it goes to the fan via the NPN transistor.

I'm trying to figure out what that AGP pin does. Maybe 5v or 12v.

It looks like perhaps something caused the old fan to draw too much current or it got hit with a spike and it burnt that track out or the little transistor failed and shorted out with to much voltage getting sent out.

Might be worth checking and components that come off that trace upstream and down stream of it, make sure there are not any other damaged parts.

The pads on Q200 look too smooth for it to have blown or even be unsoldered... are you sure the disconnected trace doesn't go directly to the fan header?

If it´s B2 contact, then it is +5V line.

Ydee wrote on 2024-10-13, 09:03:

If it´s B2 contact, then it is +5V line.

It's A2 since it's on the back side of the card. That's the line for the computer to detect whether the video card is AGP 4x capable. On the card it's hooked to Ground and because that line is burned and no longer hooks to Ground, the computer will probably only run the card in AGP 2x mode.

Here's the fan circuit for the Geforce 3 which remains the same for the Ti500. Pin A1 on the AGP slot is 12v and that hooks to the positive side of the fan. The NPN transistor hooks to a GPIO line on the GPU so that it can control the fan through PWM, pulsing it high or low turns the fan on/off by having that transistor turn on to connect the fan's negative pin to Ground. Do that fast enough and you have working fan speed control.

edit: trying to figure out the history of these cards is always tough. I just spotted that mine has flux around the two polymer capacitors at the edge of the card and I don't think I put that there. I wonder why someone would resolder those?
And I don't understand how that NPN transistor could not be present but also look so clean in that area if it was removed. There's no way that the fan can work without it because the fan's ground pin has no path to ground except through that.

Either way, something I've done on cards without fans and without that transistor is bridge the board-ground and fan-ground with a piece of wire, basically making the ground path always there so the fan works without fan control.

Thermalwrong wrote on 2024-10-13, 13:06:

And I don't understand how that NPN transistor could not be present but also look so clean in that area if it was removed. There's no way that the fan can work without it because the fan's ground pin has no path to ground except through that.

Yeah very strange there.... here is the exact same card. http://hw-museum.cz/vga/174/nvidia-geforce3-ti-500

I recognize the markings/stickers and they are cards they used in Dell machines.

Sorry all, haven’t had time to come back to this card. Will respond to everyone on the weekend. FYI, Windows is reporting this card is running at 4x AGP. I did tell the BIOS to enable 4x AGP, so maybe that pin isn’t used for detection if the speed is defined is manually in the BIOS?

I also ordered this transistor as it was cheap and delivery should be quick. Not sure if it will work. I guess if the pin out is different I could blow the card? https://www.ebay.com.au/itm/362717788579

If it's an actual MMBT2222A then the pinout is wrong. https://www.onsemi.com/pdf/datasheet/mmbt2222lt1-d.pdf
Base and emitter are switched in the version mounted on my card. If a MMBT2222A with standard pinout is mounted there, it will not "blow" the card but it won't do anything useful either. The base would be connected directly to ground which will keep the transistor off, same as if it wasn't there.
What you *could* do if you have the skill, is to mount a standard pinout part upside-down, i.e. with the face where the markings are, pointing down. 😜 You would need to bend all the pins down so they contact the PCB so they can be soldered.

An easier way to cheat the problem though, is to use a cable adapter and connect the fan to a molex connector from the PSU instead. It will run at constant speed, but better than not running at all.

stamasd wrote on 2024-10-17, 15:40:

If it's an actual MMBT2222A then the pinout is wrong. https://www.onsemi.com/pdf/datasheet/mmbt2222lt1-d.pdf Base and emitter ar […]
Show full quote

If it's an actual MMBT2222A then the pinout is wrong. https://www.onsemi.com/pdf/datasheet/mmbt2222lt1-d.pdf
Base and emitter are switched in the version mounted on my card. If a MMBT2222A with standard pinout is mounted there, it will not "blow" the card but it won't do anything useful either. The base would be connected directly to ground which will keep the transistor off, same as if it wasn't there.
What you *could* do if you have the skill, is to mount a standard pinout part upside-down, i.e. with the face where the markings are, pointing down. 😜 You would need to bend all the pins down so they contact the PCB so they can be soldered.

An easier way to cheat the problem though, is to use a cable adapter and connect the fan to a molex connector from the PSU instead. It will run at constant speed, but better than not running at all.

I appreciate your help! Going further back up the post, did you say the pin out for a 2N2222 is different as well? I was going to get this as well https://www.ebay.com.au/itm/405020168796

I actually have 2x 92mm Noctura fans in the adjacent PCI slot cooling the card (total overkill 🤣) so I don’t really need to repair the fan. However, I would like to repair it because I enjoy fixing stuff. I have all the tools to do it, just need to get the correct transistor.

The pinout of the parts you ordered is the standard one for 2N2222, MMBT2222, PMBT2222 etc. But the parts on the Ti500 (at least on mine) use an alternative pinout which is more rare, with E and B locations switched.

Again, if you feel comfortable doing it - take one of the standard pinout parts, flip it upside down so that the E and B switch positions, and push gently the pins down to the opposite side until they touch the PCB so they can be soldered. 😀
With C pointing down, the pin order from left to right should be B then E, whereas in the standard pinout it would be E then B. By flipping the chip over you can get that. Be gentle with the pins, in the SOT23 package they are fragile. You probably don't need to bend them all the way over, you can bridge the gaps to the pads below with bigger than usual blobs of solder.