Motherboard fuses - missing?

Mobos often have empty spaces where it looks like something could go. Not every model uses every space. RTFM:

I have RTFM, but TFM doesn't mention the fuse, and I doubt that these missing fuses are for any missing functions. I've also never heard of TFM ever going into this much detail about the hardware.

If they are not there you probably don't need them.

Yes, but why specifically is the circuit board laid out for those fuses?

Because it's cheaper to make one board, and then stuff it as needed, than have to make a different board for every variant, or when a small change is necessary.

Let's say they make 100,000 boards. They start stuffing and run out of a specific part at the 10,000 mark. If they can't get the part that fits, then they have to scrap the remaining 90,000 boards. But when they have foresight, they have designed the board to take some different parts sizes just in case.

Or, and this is common in consumer equipment, one board has some features that the other doesn't. So long as it doesn't add too much to the board space, it's cheaper to have one board that has all the possibilities than multiple boards.

So the fuses that are "missing" may exist on the board in a different form. Or they may be part of feature that isn't part of what you bought, so you don't get it.

Meanwhile, someone else might have the same board, and have those fuses in place while fuses in a different package elsewhere are "missing". The traces on the board simply put both in parallel so what is available can fit the board. Or, they have some extra feature that requires some of the "missing" parts, so the space is filled.

Michael

But has someone actually traced the board? Like I said, boards can be laid out to permit different size parts. You do not see jumpers across the component pads. The traces take circuitous routes, and the parts may not be right next to the alternative component pads.

If jumpers are needed, I suspect they'd be laid out as jumpers, rather than expecting a machine to jam in jumpers across pads laid out for components. And the jumper pads may not be right next to the "missing" components.

Hence unless someone gets out an ohmmeter and traces the circuit board, they can't be sure what's happening.

Michael

I doubt it.

Not forgetting that you need to not only trace both sides at the same time. remembering those little holes are actually links from one side to another, but also find out whethere there are layers in the middle too.

While that seems logical in a good design, what we have in these cases is "usually" a board layout that allows for the various fuses, but then later the fuses are not added (shaves a couple cents cost) but rather that fuse location has a jumper wire, or just traced over.

I agree, but still it's curious that this particular board has this setup. He and I have both noted many boards with the fuses there OR missing where they had used more obvious method of continuity of the 5V supply by merely bridging the pad(s) gap where a fuse could've gone.

Usually not, the 5V power plane does not extend that far and generally singular 5V traces are not put in middle layers for such ports. "Maybe" they did it, but if so this is first time I (or apparently LM&C) has seen it.