more likely a bipolar transistor or fet.

songoffall wrote on 2025-02-13, 20:36:

My Acorp 6VIA81 does aren't over yet :)) […]
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My Acorp 6VIA81 does aren't over yet 😀)

Apparently the fan headers on the motherboard aren't working. I took a look at it, and there's an SMD component blown on the board:

The attachment IMG_2279.jpeg is no longer available

Apparently a 2AZ zener diode, but can't be sure.

Is there a recommended guideline on wiring these headers the right way? Does anyone have a similar board to help me identify either the part or an equivalent part?

It depends how it's implemented, other boards I've seen from around then use a transistor to turn the fan on and off. Do that rapidly enough and you've got PWM / voltage-based speed control for the fan header.

The trouble is a big enough fan might draw too much current for the transistor or maybe an event happens that causes it to go high-current-draw and the little transistor blows.

To figure out what you need, check the fan header pinout check against this: https://pinoutguide.com/Motherboard/MbCpuFan_pinout.shtml
The left pin (pin1 of the fan header) should hook to ground, if it doesn't then the burned transistor should be an NPN one or perhaps a small n-channel mosfet. Because that transistor would only be connected when the board's powered and the transistor is working.
The middle pin should hook to 12v and if that doesn't then it'd be a pnp transistor.

You can probably identify similar pairs of transistors on other boards, perhaps you can just grab similar spares from a dead board. Something I've done before now on similar fan control circuits is just jumper the connection from the top of the burned transistor (output pin) to the lower-right pad, so the transistor is bypassed.
Probably need to remove the burned transistor if you do that of course 😀

So I cross-referenced with another board, it is a 2AZ, a SOT-23 zener.

Even though I could have gone simpler - there are two more fan headers on this board and the components aren't blown.

But those headers aren't functioning either. Which is interesting. I'll keep investigating further - maybe the BIOS being corrupted on update is connected to this, like voltages being off or something.

The board designator is "Q3", which means it *has to be* a switching device of some sort - either MOSFET or BJT, as weedeewee mentioned. So it CANNOT be a Zener.

*edit*
Looking at my list of SOT-23 datasheets, "2A" is commonly used for MMBT3906 transistors (PNP type BJT), so I think that's what you have likely.
/edit

Now, I am pretty sure I have never seen early boards PWM-drive fans, so I never understood why some (very few, like Intel, for example) liked to use a circuit like this. The boards that had this kind of control either fully enabled or fully disabled the fans... but nothing in between. I guess just to keep the fan noise down in S1 standby mode (since not many early boards supported S3 standby/sleep.)

Whatever the case, I suggest not to worry too much about it. If you want just the fan headers to work, put a short piece of jumper wire between Drain and Source (if Q3 is a MOSFET) or Collector and Emitter (if Q3 is a BJT.) Most SOT-23 switching devices have these at the top pin and rightmost pin, respectively. But before you go jumper things blindly, perhaps it might be a good idea to use a multimeter to double-check what pin on Q3 goes to what. On a normal always-powered 3-pin fan hearder, you have ground, 12V, and RPM monitor for the 3 pins. On a header like this where a MOSFET/BJT is used, either the ground pin or the "12V"/power pin (middle pin of the fan header) will connect to one of the pins of Q3. There's TWO possibilities, really:
1) if Q3 is a P-channel MOSFET or PNP BJT, most likely the middle pin of the fan header will be connected to the top-most pin on Q3 (Drain/Collector).
2) if Q3 is a N-channel MOSFET or NPN BJT, most likely the "ground" pin of the fan header (one of the outer pins) will be connected to the top-most pin of Q3 (again, Drain/Collector.)
And to further verify, the right most pin of Q3 should connect to either 12V rail (if case 1 applies above) or ground (if case 2 applies above.)

momaka wrote on 2025-02-14, 23:44:

The board designator is "Q3", which means it *has to be* a switching device of some sort - either MOSFET or BJT, as weedeewee me […]
Show full quote

The board designator is "Q3", which means it *has to be* a switching device of some sort - either MOSFET or BJT, as weedeewee mentioned. So it CANNOT be a Zener.

*edit*
Looking at my list of SOT-23 datasheets, "2A" is commonly used for MMBT3906 transistors (PNP type BJT), so I think that's what you have likely.
/edit

Now, I am pretty sure I have never seen early boards PWM-drive fans, so I never understood why some (very few, like Intel, for example) liked to use a circuit like this. The boards that had this kind of control either fully enabled or fully disabled the fans... but nothing in between. I guess just to keep the fan noise down in S1 standby mode (since not many early boards supported S3 standby/sleep.)

Whatever the case, I suggest not to worry too much about it. If you want just the fan headers to work, put a short piece of jumper wire between Drain and Source (if Q3 is a MOSFET) or Collector and Emitter (if Q3 is a BJT.) Most SOT-23 switching devices have these at the top pin and rightmost pin, respectively. But before you go jumper things blindly, perhaps it might be a good idea to use a multimeter to double-check what pin on Q3 goes to what. On a normal always-powered 3-pin fan hearder, you have ground, 12V, and RPM monitor for the 3 pins. On a header like this where a MOSFET/BJT is used, either the ground pin or the "12V"/power pin (middle pin of the fan header) will connect to one of the pins of Q3. There's TWO possibilities, really:
1) if Q3 is a P-channel MOSFET or PNP BJT, most likely the middle pin of the fan header will be connected to the top-most pin on Q3 (Drain/Collector).
2) if Q3 is a N-channel MOSFET or NPN BJT, most likely the "ground" pin of the fan header (one of the outer pins) will be connected to the top-most pin of Q3 (again, Drain/Collector.)
And to further verify, the right most pin of Q3 should connect to either 12V rail (if case 1 applies above) or ground (if case 2 applies above.)

Thanks, friend. I'll do that; but first I have to understand why the other headers aren't working - the ones without blown-up parts. As there are also problems with updating the BIOS (which just zeroes the BIOS, and the BIOS chip itself is functional), I'm going to reflow the SuperIO chip first, see what happens.

^ My guess is the BIOS isn't starting, so all of the fans stay disabled.

momaka wrote on 2025-02-23, 21:52:

^ My guess is the BIOS isn't starting, so all of the fans stay disabled.

Even when the BIOS was starting, the fans weren't working 😀) Also, the BIOS boot sector is still there.