Motherboard fuses - missing?

[larry moe 'n curly]

I have an Asrock (budget Asus) K7VT4A Pro ATX motherboard with three
empty spaces where it seems that fuses would normally go.

They're all at the rear, near the I/O ports. At locations F1 and F2 I
measure 5V across their solder pads, while at location F2 I measure 0V
between them (each solder pad is at 4.8V).

I've seen resettable fuses installed in locations like this on some
other motherboards, and I've even seen some with soldered jumpers.

What's going on here?

 

[Tom Biasi]

I have an Asrock (budget Asus) K7VT4A Pro ATX motherboard with three
empty spaces where it seems that fuses would normally go.

They're all at the rear, near the I/O ports. At locations F1 and F2 I
measure 5V across their solder pads, while at location F2 I measure 0V
between them (each solder pad is at 4.8V).

I've seen resettable fuses installed in locations like this on some
other motherboards, and I've even seen some with soldered jumpers.

What's going on here?

Mobos often have empty spaces where it looks like something could go. Not
every model uses every space.
RTFM: http://www.asrock.com.tw/Drivers/Manual/K7VT4APro_um.pdf

 

[larry moe 'n curly]

Mobos often have empty spaces where it looks like something could go. Not
every model uses every space.
RTFM: http://www.asrock.com.tw/Drivers/Manual/K7VT4APro_um.pdf

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.

 

[Tom Biasi]

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.

 

[larry moe 'n curly]

Mobos often have empty spaces where it looks like something could go. Not

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

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

 

[kony]

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

It's easier to make one board design that's a jack of all
trades, then later modify it only the (least) amount
necessary to meet some requirement or cut cost or (whatever
the scenario). Did you determine how the (typically fused)
ports are getting power since those fuse positions are
unfilled?

 

[Michael Black]

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

 

[Conor]

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

**** sake...you really have no idea do you?

It is far cheaper for manufacturers to design and stock one PCB to work
across many models than to design and make a PCB for each individual
model.


--
Conor

If Pac-Man affected us as kids, we'd all be running around in darkened
rooms, munching magic pills and listening to repetitive electronic
music.

 

[larry moe 'n curly]

**** sake...you really have no idea do you?

It is far cheaper for manufacturers to design and stock one PCB to work
across many models than to design and make a PCB for each individual
model.

I realize that, but in this case I can't imagine why the manufacture
would vary the design because the fuses are for keyboard (and maybe
mouse), USB, and Ethernet, and this particular mobo doesn't seem to
have any missing features for these because it does allow wake on
keyboard/mouse/USB/Ethernet.

 

[Conor]

I realize that, but in this case I can't imagine why the manufacture
would vary the design because the fuses are for keyboard (and maybe
mouse), USB, and Ethernet, and this particular mobo doesn't seem to
have any missing features for these because it does allow wake on
keyboard/mouse/USB/Ethernet.

For that particular model.


--
Conor

If Pac-Man affected us as kids, we'd all be running around in darkened
rooms, munching magic pills and listening to repetitive electronic
music.

 

[kony]

For that particular model.

Yes, BUT for that particular model the fuses ARE missing.
Our presumptions about why they might have the fuse spots
still doesn't address his original query.

 

[Ken Weitzel]

Yes, BUT for that particular model the fuses ARE missing.
Our presumptions about why they might have the fuse spots
still doesn't address his original query.

Hi...

Just thinking out loud... not only different models, but
that one board design will have been designed for use in
different parts of the world.

Perhaps outher countries have different code requirements for
things "extended from" the main chassis?

Wouldn't explain a missing fuse all by itself, but perhaps
one jumper is eliminated elsewhere and then the fuse is
required...

Just a thought.

Ken

 

[kony]

Hi...

Just thinking out loud... not only different models, but
that one board design will have been designed for use in
different parts of the world.

Perhaps outher countries have different code requirements for
things "extended from" the main chassis?

Wouldn't explain a missing fuse all by itself, but perhaps
one jumper is eliminated elsewhere and then the fuse is
required...

Just a thought.

Ken

It's an interesting thought but the remaining question is
still, if the fuse isn't installed _and_ the fuse location
isn't jumpered, why and where did they reroute the power for
the ports? "Usually" when a fuse is (or isn't) used, the
power is still delivered on same traces either way, the
circuit change is prior to that point.

 

[larry moe 'n curly]

Just thinking out loud... not only different models, but
that one board design will have been designed for use in
different parts of the world.

Perhaps outher countries have different code requirements for
things "extended from" the main chassis?

Wouldn't explain a missing fuse all by itself, but perhaps
one jumper is eliminated elsewhere and then the fuse is
required...

That makes sense.

This is the first time I've seen a mobo made for fuses where the
left-out fuses weren't substituted with jumper wires (PC Chips, some
ECS) or copper traces between each fuse location's solder pads.

 

[Curly Howard]

....

That makes sense.

This is the first time I've seen a mobo made for fuses where the
left-out fuses weren't substituted with jumper wires (PC Chips, some
ECS) or copper traces between each fuse location's solder pads.

I can't tell you why, or how. But a suggestion might help.

I've been doing PC Repair for a long time. And I've often seen the same
mobo design used by different manufacturers. And in the same
manufacturer, I've seen boards that are the same layout, but different in
the number of components, the one with less components on the board being
the cheaper version.

What I would try to do is find other boards on the manufacturers website
with the same layout. Often they include a picture of the board (not
always the best rez) that might show you what you're looking for.

I've often seen boards that are the same layout from Chaintech, PC Chips,
Asus, Epox and others. It's a pain in the tukas, but you might also be
able to find a board with the same layout but different features with one
of these other vendors.

The boards will always be the same size physically, and have the same
locations of the CPU socket and primary chipset(s). But they may have a
different number of bus interfaces, or memory sockets. And often they
have different bioses. However, I have (in the past) been able to use
one vendor's drivers to make a piece of hardware work.

Hope that helps lmac.

Curly

yak, yak, yak, oooooohh....

 

[Conor]

Yes, BUT for that particular model the fuses ARE missing.
And?

Our presumptions about why they might have the fuse spots
still doesn't address his original query.

Because its a pointless one. I could rabbit on incessantly about
buffers etc but what's the point?


--
Conor

If Pac-Man affected us as kids, we'd all be running around in darkened
rooms, munching magic pills and listening to repetitive electronic
music.

 

[kony]

And?

And, the ports DO work. It was not a matter of omitting
fuses or jumpers for features not present if these are as
described. So, you have to have an alternate way of getting
the power to those ports if it's not traveling the same path
as (practically any) motherboard out there. Perhaps if
you'd more carefully examined more boards you'd appreciate
the distinction, as larry moe 'n curly did have a valid
point and had also recognized that when the fuses aren't
employed there IS a jumper in it's place or copper track
across the pads. This particular board he has is unique in
this respect.

Because its a pointless one. I could rabbit on incessantly about
buffers etc but what's the point?

The point is that some of us are interested in motherboard
layout/design/etc... it is a hardware group.

 

[Franc Zabkar]

For that particular model.

What is it about the OP's post that you don't understand? He has
stated that all the motherboard's IO functions are operational. This
means that *all* devices are getting their power from the motherboard,
despite several fuse locations being unpopulated, ie *open*. So the
OP's question as to what function these missing fuses would have
performed is a valid and logical one.


- Franc Zabkar

 

[Franc Zabkar]

For that particular model.

What is it about the OP's post that you don't understand? He has
stated that all the motherboard's IO functions are operational. This
means that *all* devices are getting their power from the motherboard,
despite several fuse locations being unpopulated, ie *open*. So the
OP's question as to what function these missing fuses would have
performed is a valid and logical one.


- Franc Zabkar

 

[Jumpster Jiver]

I realize that, but in this case I can't imagine why the manufacture
would vary the design because the fuses are for keyboard (and maybe
mouse), USB, and Ethernet, and this particular mobo doesn't seem to
have any missing features for these because it does allow wake on
keyboard/mouse/USB/Ethernet.

In this case, maybe a certain country has different safety standards
that require the keyboard, mouse, etc. to be fused, so on the models
sent to that country they are fused, and the same model marketed in
other countries leaves the fuse out and maybe puts a cheaper jumper in
to save money on components.
In large quantities the fuse may cost a penny and a jumper may cost 1/10
of a penny. Over hundreds of thousands of boards it makes a difference.