Faulty case or PSU or both?

[as mellow as a horse]

While testing a motherboard a few months back, the reset cable suddenly
started melting! Because the case I was using was only for testing, I just
started plugging in the reset cable instead and using the reset switch to
power on and off.

But today that melted too! The case is now useless, but I was wondering
whether the problem was faulty wiring or the PSU? I don't know much about
wiring or PSUs, so I'm not sure if it's worth dumping the psu as well as the
case, or holding on to it.

 

[kony]

While testing a motherboard a few months back, the reset cable suddenly
started melting! Because the case I was using was only for testing, I just
started plugging in the reset cable instead and using the reset switch to
power on and off.

But today that melted too! The case is now useless, but I was wondering
whether the problem was faulty wiring or the PSU? I don't know much about
wiring or PSUs, so I'm not sure if it's worth dumping the psu as well as the
case, or holding on to it.

You don't happen to live in a microwave oven do you?
I've heard about those Pillsbury Oven Gnomes but never met one.

You might be quite lucky the motherboard still works, that's a lot of
current to melt the wires. I would've expected the traces on the board to
peel off or burn through before the wires melted. Is it possible you have
an extra standoff mounted under the board, shorting it out? It's not
common for a dodgy power supply to cause that kind of damage, but the
(wires themselves) in the case shouldn't be the issue.

Your local mom-n-pop computer shop may have some leaded switches lying
around, more often than not they're more similar/same than different, so
if you source a couple of switches/leads to replace those melted, your
case should be operational again, though you'd better figure out WHY the
cables were melting first.

At what point along the cables were they melting?
If up near the switches, you might have faulty switches or they're poorly
mounted, intermittently shorting against the case wall, though that
should've been turning the board on/off or resetting it.

 

[Donald R. Kasper]

Dump that PSU as well as your case. Because if it is your wiring causing
that problem is just screwed your PSU. Hell I would also tell you to invest
in a UPS and a power purifier.

 

[as mellow as a horse]

You don't happen to live in a microwave oven do you?
I've heard about those Pillsbury Oven Gnomes but never met one.

You might be quite lucky the motherboard still works, that's a lot of
current to melt the wires. I would've expected the traces on the board to
peel off or burn through before the wires melted. Is it possible you have
an extra standoff mounted under the board, shorting it out? It's not
common for a dodgy power supply to cause that kind of damage, but the
(wires themselves) in the case shouldn't be the issue.

Your local mom-n-pop computer shop may have some leaded switches lying
around, more often than not they're more similar/same than different, so
if you source a couple of switches/leads to replace those melted, your
case should be operational again, though you'd better figure out WHY the
cables were melting first.

At what point along the cables were they melting?
If up near the switches, you might have faulty switches or they're poorly
mounted, intermittently shorting against the case wall, though that
should've been turning the board on/off or resetting it.

At the time of the 1st incident, I was testing LOTS of boards and had no
viable option but to test them outside of the case on anti-static wrapping.
Today I was too busy to try the particular board inside the case and did the
same thing. In both cases, the boards were faulty.

It's only a cheap case and I've got some value out of it (12 months old),
and it's probably more trouble than it's worth messing with switches. I'll
probably keep the PSU as emergency spare.

 

[w_tom]

A reset line is typically connected only to resistors and
logic gate inputs on motherboard. Milliamps - current barely
enough to light an LED. Amps would be required to melt wire.

What you are calling a Reset cable - describe in exact
detail what you have connected to? Even every number on
motherboard connector, motherboard model number - something so
that one can even begin to understand your question. How about
a personal picture or a web site of your motherboard?

Power supply failure? Nonsense if a supply was purchased on
technical merit; not just on price. Intel specs say every
power supply can have all outputs shorted together and still
power supply is not damaged; making a power conditioner
recommendation is irrelevant. Not apparent what it is you are
cooking; even what you call a reset wire.

 

[kony]

At the time of the 1st incident, I was testing LOTS of boards and had no
viable option but to test them outside of the case on anti-static wrapping.

Do NOT put the board on anti-static wrapping.... anti-static wrapping, by
definition, conducts electricity... that might be the whole problem.

Today I was too busy to try the particular board inside the case and did the
same thing. In both cases, the boards were faulty.

Are you sure of that? They might've been fine before you put them on the
anti-static wrapping, or they may still work fine if not placed on it.

It's only a cheap case and I've got some value out of it (12 months old),
and it's probably more trouble than it's worth messing with switches. I'll
probably keep the PSU as emergency spare.

Trouble? It's really not that bad/hard/etc, but if you didn't like the
case anyway I suppose that's as good an excuse as any to replace it.

 

[as mellow as a horse]

A reset line is typically connected only to resistors and
logic gate inputs on motherboard. Milliamps - current barely
enough to light an LED. Amps would be required to melt wire.

What you are calling a Reset cable - describe in exact
detail what you have connected to? Even every number on
motherboard connector, motherboard model number - something so
that one can even begin to understand your question. How about
a personal picture or a web site of your motherboard?

Going back to late last year, I hooked up a board I wanted to test to the
front panel of my test case. As for any other board, I just connected the
power sw lead to the power sw pins on the mobo. As I recall, the board
POSTed and got as far as prompting for a system disk. Before I could do
anything else, I noticed a burning smell and smoke. I though it was the
board or cpu, but then I noticed the power sw lead was actually melting and
the smoke was coming from that.

After that I just used the reset lead to plug into the power sw pins, and
had no problems until yesterday when the same thing happened again, but with
another board.

The power and reset switches on the front panel are as good as useless as
they are near impossible to push in. I guess the melting occurred all the
way along the cable, although the part that plugs into the pins is
unaffected.

Power supply failure? Nonsense if a supply was purchased on
technical merit; not just on price. Intel specs say every
power supply can have all outputs shorted together and still
power supply is not damaged; making a power conditioner
recommendation is irrelevant. Not apparent what it is you are
cooking; even what you call a reset wire.

I think I said in the OP that I don't know diddly about electrics. Bits and
bytes, sure. Volts, watts, amps? Totally foreign to me.

The case and psu were bargain basement and the psu came with the case. I
bought an enermax psu for my regular pc that cost more than twice as much as
the test case and psu together.

 

[Guest]

While testing a motherboard a few months back, the reset
cable suddenly started melting! Because the case I was
using was only for testing, I just started plugging in
the reset cable instead and using the reset switch to
power on and off.

But today that melted too! The case is now useless, but
I was wondering whether the problem was faulty wiring or
the PSU? I don't know much about wiring or PSUs, so I'm
not sure if it's worth dumping the psu as well as the
case, or holding on to it.

The reset switch merely triggers an input to a chip on the
motherboard, meaning even in the worst case only a few milliamps
should flow through it, and this is far, far too little current to
cause any noticeble heating of the wires or switch. So I think that
the chip was defective and was shorting directly to +5V or +3.3V. I
don't know how it became defective, but I suspect that static
electricity either shorted a transistor or even a diode meant to
protect against static. What measures did you take to ensure that the
reset and power buttons were discharged of static before you connected
them to the motherboard? For each switch, did you plug a loop of wire
into both of its connector sockets and then ground that loop to the
motherboard's ground? Of course, remove that loop before connecting
the switch to the motherboard. Also were you discharged when you
pressed the power or reset button, to prevent sending high voltage
into it?

If you want to protect the wiring of the buttons, consider wiring a
200-300 ohms resistor, 1/4 watt or larger, in series with one of the
wires of each switch. This may also help protect the chip, but 1,000
ohms would protect better but may not trigger the power or reset
functions reliably.