# What happened to this motherboard?

P

#### [email protected]________.com

Jan 1, 1970
0
A while back I bought a used 500mhz computer on Ebay. (that was my
big mistake). When I got it, it worked well, except for the floppy
drive. I contacted the seller immediately and he sent me another
floppy drive to replace the bad one. I replaced the drive and turned
it on. It worked fine but since I wanted to add another harddrive (as
soon as I got one), I left the cover off the case. That turned out to
be a good thing, because I was sitting at my desk on the web when I
noticed a hot burnt odor. Then I saw smoke. I looked at the computer
and saw smoke coming off the motherboard. There are these donut
looking things on the board. They look like a white lifesaver candy
wound with 20 or 30 loops of a fairly thick enamelled wire (actually
not all that thick, probably a 20 gauge). Oddly enough, the computer
continued to work the whole time, and I know that because I saved
whatever I was typing before I shut off the power. I found all the
enamel burned off the wire on that coil and it was black. I was glad
the cover was off the case so I could see what was happening.

I carefully looked for anything that might create a short and found
nothing. I got my fire estinguisher (just in case), and turned the
computer back on. It booted up, and worked fine. I turned it on and
off several more times, and it still worked, and I never saw more
smoke. The seller would not replace it because it was 2 ot 3 weeks
later by then.

What could have caused this? What are those coild called and what is
their purpose. It seems there are 2 or 3 of them on all motherboards.

Needless to say, I do not use this computer. I dont trust it. I just
took out all the drives, ram, and cards and put them on another
motherboard. I know I can use that case again, but question the power
supply. I definately will not use the motherboard again, and worry

Anyone have any idea what caused this? I'm just curious more than
anything else. I figure the MB is best going into the trash, and I
have a faster CPU now too.

Thanks

Plumber

T

#### Tim

Jan 1, 1970
0
plumber1 said:
A while back I bought a used 500mhz computer on Ebay. (that was my
big mistake). When I got it, it worked well, except for the floppy
drive. I contacted the seller immediately and he sent me another
floppy drive to replace the bad one. I replaced the drive and turned
it on. It worked fine but since I wanted to add another harddrive (as
soon as I got one), I left the cover off the case. That turned out to
be a good thing, because I was sitting at my desk on the web when I
noticed a hot burnt odor. Then I saw smoke. I looked at the computer
and saw smoke coming off the motherboard. There are these donut
looking things on the board. They look like a white lifesaver candy
wound with 20 or 30 loops of a fairly thick enamelled wire (actually
not all that thick, probably a 20 gauge). Oddly enough, the computer
continued to work the whole time, and I know that because I saved
whatever I was typing before I shut off the power. I found all the
enamel burned off the wire on that coil and it was black. I was glad
the cover was off the case so I could see what was happening.

I carefully looked for anything that might create a short and found
nothing. I got my fire estinguisher (just in case), and turned the
computer back on. It booted up, and worked fine. I turned it on and
off several more times, and it still worked, and I never saw more
smoke. The seller would not replace it because it was 2 ot 3 weeks
later by then.

What could have caused this? What are those coild called and what is
their purpose. It seems there are 2 or 3 of them on all motherboards.

Needless to say, I do not use this computer. I dont trust it. I just
took out all the drives, ram, and cards and put them on another
motherboard. I know I can use that case again, but question the power
supply. I definately will not use the motherboard again, and worry

Anyone have any idea what caused this? I'm just curious more than
anything else. I figure the MB is best going into the trash, and I
have a faster CPU now too.

Thanks

Plumber
Those are probably inductors used to limit noise on the DC power lines.
If they overheated, that usually indicates a fault on the motherboard.
It takes a great deal of energy to burn those lines, so I would look for
a damaged regulator or shorted capacitor on the board. The problem may
be a short on one of the inside layers of the board as well, so you may
have to remove the board and try to look through it. If one of the
layers is a ground plane, you will not be able to see through the board.

- Tim -

D

#### David

Jan 1, 1970
0
Tim said:
Those are probably inductors used to limit noise on the DC power lines.
If they overheated, that usually indicates a fault on the motherboard.
It takes a great deal of energy to burn those lines, so I would look for
a damaged regulator or shorted capacitor on the board. The problem may
be a short on one of the inside layers of the board as well, so you may
have to remove the board and try to look through it. If one of the
layers is a ground plane, you will not be able to see through the board.

- Tim -

Actually the most of the inductors described are not noise filters at all,
but part of a switching power supply regulator that converts either 5 or 3.3
volt supplies to lower voltages such as 1.5 volts for the CPU. They often
operate at high currents (perhaps as much as 10 - 20 amperes). There are
also some boards that have regulators to generate higher voltages for other
components on the board such as built in audio or RS232 ports. I have never
seen one get hot enough to cause smoke without also something else wrong. My
guess is that particular regulator was associated with something other than
the main CPU/memory system or else the machine would not run. Do all of the
I/O ports, built in peripherals, and add-on cards operate?

David

D

#### Dave

Jan 1, 1970
0
David said:
Actually the most of the inductors described are not noise filters at all,
but part of a switching power supply regulator that converts either 5 or
3.3 volt supplies to lower voltages such as 1.5 volts for the CPU. They
often operate at high currents (perhaps as much as 10 - 20 amperes). There
are also some boards that have regulators to generate higher voltages for
other components on the board such as built in audio or RS232 ports. I
have never seen one get hot enough to cause smoke without also something
else wrong. My guess is that particular regulator was associated with
something other than the main CPU/memory system or else the machine would
not run. Do all of the I/O ports, built in peripherals, and add-on cards
operate?

David

New motherboards with CPUs and often CPU fans can be had at retailers such
as Frys (they also have a a web) for $80 to$100. I have built many PCs with
these: P4s, AMD etc,

J

#### James Sweet

Jan 1, 1970
0
A while back I bought a used 500mhz computer on Ebay. (that was my
big mistake). When I got it, it worked well, except for the floppy
drive. I contacted the seller immediately and he sent me another
floppy drive to replace the bad one. I replaced the drive and turned
it on. It worked fine but since I wanted to add another harddrive (as
soon as I got one), I left the cover off the case. That turned out to
be a good thing, because I was sitting at my desk on the web when I
noticed a hot burnt odor. Then I saw smoke. I looked at the computer
and saw smoke coming off the motherboard. There are these donut
looking things on the board. They look like a white lifesaver candy
wound with 20 or 30 loops of a fairly thick enamelled wire (actually
not all that thick, probably a 20 gauge). Oddly enough, the computer
continued to work the whole time, and I know that because I saved
whatever I was typing before I shut off the power. I found all the
enamel burned off the wire on that coil and it was black. I was glad
the cover was off the case so I could see what was happening.

I carefully looked for anything that might create a short and found
nothing. I got my fire estinguisher (just in case), and turned the
computer back on. It booted up, and worked fine. I turned it on and
off several more times, and it still worked, and I never saw more
smoke. The seller would not replace it because it was 2 ot 3 weeks
later by then.

What could have caused this? What are those coild called and what is
their purpose. It seems there are 2 or 3 of them on all motherboards.

Needless to say, I do not use this computer. I dont trust it. I just
took out all the drives, ram, and cards and put them on another
motherboard. I know I can use that case again, but question the power
supply. I definately will not use the motherboard again, and worry

Anyone have any idea what caused this? I'm just curious more than
anything else. I figure the MB is best going into the trash, and I
have a faster CPU now too.

Thanks

Plumber

Something has shorted on the motherboard, it's not worth trying to repair
one so old, but the rest of the components will be fine.

C

#### catguy

Jan 1, 1970
0
A while back I bought a used 500mhz computer on Ebay. (that was my
big mistake). When I got it, it worked well, except for the floppy
drive. I contacted the seller immediately and he sent me another
floppy drive to replace the bad one. I replaced the drive and turned
it on. It worked fine but since I wanted to add another harddrive (as
soon as I got one), I left the cover off the case. That turned out to
be a good thing, because I was sitting at my desk on the web when I
noticed a hot burnt odor. Then I saw smoke. I looked at the computer
and saw smoke coming off the motherboard. There are these donut
looking things on the board. They look like a white lifesaver candy
wound with 20 or 30 loops of a fairly thick enamelled wire (actually
not all that thick, probably a 20 gauge). Oddly enough, the computer
continued to work the whole time, and I know that because I saved
whatever I was typing before I shut off the power. I found all the
enamel burned off the wire on that coil and it was black. I was glad
the cover was off the case so I could see what was happening.

I carefully looked for anything that might create a short and found
nothing. I got my fire estinguisher (just in case), and turned the
computer back on. It booted up, and worked fine. I turned it on and
off several more times, and it still worked, and I never saw more
smoke. The seller would not replace it because it was 2 ot 3 weeks
later by then.

What could have caused this? What are those coild called and what is
their purpose. It seems there are 2 or 3 of them on all motherboards.

Needless to say, I do not use this computer. I dont trust it. I just
took out all the drives, ram, and cards and put them on another
motherboard. I know I can use that case again, but question the power
supply. I definately will not use the motherboard again, and worry

Anyone have any idea what caused this? I'm just curious more than
anything else. I figure the MB is best going into the trash, and I
have a faster CPU now too.

Thanks

Plumber

Look for the buldging electrolytic capacitors....Paul

J

#### Jeroni Paul

Jan 1, 1970
0
I have seen old Pentiums run at the wrong core voltage, and they would
work, maybe hotter or less stable. It could be a shorted regulator
putting out 3.3V to the 1,5V line, not sure if a P III would hold that
but it might work for some time.

J

#### Jamie

Jan 1, 1970
0
A while back I bought a used 500mhz computer on Ebay. (that was my
big mistake). When I got it, it worked well, except for the floppy
drive. I contacted the seller immediately and he sent me another
floppy drive to replace the bad one. I replaced the drive and turned
it on. It worked fine but since I wanted to add another harddrive (as
soon as I got one), I left the cover off the case. That turned out to
be a good thing, because I was sitting at my desk on the web when I
noticed a hot burnt odor. Then I saw smoke. I looked at the computer
and saw smoke coming off the motherboard. There are these donut
looking things on the board. They look like a white lifesaver candy
wound with 20 or 30 loops of a fairly thick enamelled wire (actually
not all that thick, probably a 20 gauge). Oddly enough, the computer
continued to work the whole time, and I know that because I saved
whatever I was typing before I shut off the power. I found all the
enamel burned off the wire on that coil and it was black. I was glad
the cover was off the case so I could see what was happening.

I carefully looked for anything that might create a short and found
nothing. I got my fire estinguisher (just in case), and turned the
computer back on. It booted up, and worked fine. I turned it on and
off several more times, and it still worked, and I never saw more
smoke. The seller would not replace it because it was 2 ot 3 weeks
later by then.

What could have caused this? What are those coild called and what is
their purpose. It seems there are 2 or 3 of them on all motherboards.

Needless to say, I do not use this computer. I dont trust it. I just
took out all the drives, ram, and cards and put them on another
motherboard. I know I can use that case again, but question the power
supply. I definately will not use the motherboard again, and worry

Anyone have any idea what caused this? I'm just curious more than
anything else. I figure the MB is best going into the trash, and I
have a faster CPU now too.

Thanks

Plumber

W

#### w9gb

Jan 1, 1970
0
This may be educational

Personally, I would not have spent a dime for a 500 MHz PC, when Fry's area
selling brand new Pentium 4 with software for $299 (last year models being replaced by new ones). gb W #### William R. Walsh Jan 1, 1970 0 Hi! It could be a shorted regulator putting out 3.3V to the 1,5V line, not sure if a P III would hold that but it might work for some time. If the coil got hot enough to smoke, the voltage may have been held down to a much lower value by virtue of the coil's resistance. William A #### AZ Nomad Jan 1, 1970 0 A while back I bought a used 500mhz computer on Ebay. (that was my big mistake). When I got it, it worked well, except for the floppy drive. I contacted the seller immediately and he sent me another floppy drive to replace the bad one. I replaced the drive and turned it on. It worked fine but since I wanted to add another harddrive (as soon as I got one), I left the cover off the case. That turned out to be a good thing, because I was sitting at my desk on the web when I noticed a hot burnt odor. Then I saw smoke. I looked at the computer and saw smoke coming off the motherboard. There are these donut looking things on the board. They look like a white lifesaver candy Many many motherboards from that era had bad caps. Did you examine the caps for bulging and/or leaking? P #### [email protected]________.com Jan 1, 1970 0 Thanks for the link. You (and others) were correct. There are 3 caps right next to this coil and very close to some major power transistors (probably regulators). All 3 of those caps have bulged tops and there seems to be a brown stain next to one of them. Until looking at the pics on this website, I did not know what to look for. It's now obvious those 3 caps are fried. Oddly enough that motherboard still boots and runs. In fact I loaded windows and a bunch of hi-res photos and no problems. I think I am going to see if I can find three 1000uf caps and replace them. No sense trashing a working motherbd for$5
worth of caps. I wont replace the others, jsut those three. That
coil is charred but it still works. Since the windings dont touch I
dont see where it matters if the enamel is burned off. I got a
soldering iron so what the heck. Maybe I'll turn that into my Windows
98 machine. I still like using 98 when XP pisses me off, which it
does quite often.

Just curious. What exactly do those coils do? Every motherbd has
them, at least 2 of them. They are just a core with about 10
windings. All I can figure is a choke of some sort.

----------------------

G

#### GPE

Jan 1, 1970
0
Thanks for the link. You (and others) were correct. There are 3 caps
right next to this coil and very close to some major power transistors
(probably regulators). All 3 of those caps have bulged tops and there
seems to be a brown stain next to one of them. Until looking at the
pics on this website, I did not know what to look for. It's now
obvious those 3 caps are fried. Oddly enough that motherboard still
boots and runs. In fact I loaded windows and a bunch of hi-res photos
and no problems. I think I am going to see if I can find three 1000uf
caps and replace them. No sense trashing a working motherbd for $5 worth of caps. I wont replace the others, jsut those three. That coil is charred but it still works. Since the windings dont touch I dont see where it matters if the enamel is burned off. I got a soldering iron so what the heck. Maybe I'll turn that into my Windows 98 machine. I still like using 98 when XP pisses me off, which it does quite often. Just curious. What exactly do those coils do? Every motherbd has them, at least 2 of them. They are just a core with about 10 windings. All I can figure is a choke of some sort. The coils are an important part of a switching voltage regulator.... as are the capacitors. The caps are probably low ESR type. -- Ed S #### [email protected] Jan 1, 1970 0 Thanks for the link. You (and others) were correct. There are 3 caps right next to this coil and very close to some major power transistors (probably regulators). All 3 of those caps have bulged tops and there seems to be a brown stain next to one of them. Until looking at the pics on this website, I did not know what to look for. It's now obvious those 3 caps are fried. Oddly enough that motherboard still boots and runs. In fact I loaded windows and a bunch of hi-res photos and no problems. I think I am going to see if I can find three 1000uf caps and replace them. No sense trashing a working motherbd for$5
worth of caps. I wont replace the others, jsut those three. That
coil is charred but it still works. Since the windings dont touch I
dont see where it matters if the enamel is burned off. I got a
soldering iron so what the heck. Maybe I'll turn that into my Windows
98 machine. I still like using 98 when XP pisses me off, which it
does quite often.

Just curious. What exactly do those coils do? Every motherbd has
them, at least 2 of them. They are just a core with about 10
windings. All I can figure is a choke of some sort.
<snip older>

That brown stain is the acid leaking out of the cap. If it's been
there too long it will eat away the copper traces on the top side. We
have lots of Sony Digital Betacam decks at work that suffer this fate.
Many of the boards can be salvaged if discovered before any serious
damage. One guy does almost full time changing through hole and
surface mount caps. BTW he uses a Metcal soldering station with an
STTC-138 tip for through hole and STTC-126 for the SMT parts.

GG

Replies
13
Views
2K
Replies
9
Views
994
Replies
3
Views
565
Replies
2
Views
644
Replies
4
Views
715