Caps loadly popping on motherboard

**What Voltage were the exploding caps rated for? What Voltage did you measure on the supply?

Trevor Wilson

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Trevor Wilson
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In message , Marc writes

Better, many years ago Compaq 386 motherboards used very similar connectors for the system fan and lithium battery, I felt the compression from the explosion about 15 yards away.

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Clint Sharp
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Clint Sharp

Workshop, big solid-state P.A. amplifier....senior of technicians and part-owner of business replaced BIG supply electros - a little casually ! On turn-on it went REALLY bang, the long strips of paper/aluminium foil tangled in the overhead ceiling fan - hilarious after the shock subsided.

The electrolyte mist most corrosive on pretty brushed-aluminium front panels etc., of other customer equipment....more care taken afterwards with double-checking of polarity !

Reckon it might have been one of the YAMAHA P-2200 series from 20+ years ago.

Reply to
Fun Tyme

The caps are 1000uF at 10V. The power supply is meant to be 12V and the board is meant to run on 12V. Do you know if I can replace the caps with

1000uF at a higher voltage? I've got some dead boards but can only find 1 cap that is 10V at 1000uF.

Michael

Reply to
Michael C

**What Voltage did you measure across the dead caps?

The power supply is meant to be 12V and the

**What Voltage did you MEASURE on the supply?

Do you know if I can replace the caps with

**Yes, you can. What Voltage did you measure on the supply?

I've got some dead boards but can only find 1

**What Voltage did you measure on the supply?

Trevor Wilson

Reply to
Trevor Wilson

On Sat, 8 Dec 2007 14:39:14 +1100, "Michael C" put finger to keyboard and composed:

This makes no sense. If the caps are original, then obviously they weren't meant to take 12V. Either you are mistaken about the supply voltage for your board (what is its model number?), or there are separate +5V and +12V inputs, or the caps are on the output side of an onboard switchmode PSU, in which case this PSU has failed.

You may find that higher voltage caps are physically too large for your board.

- Franc Zabkar

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Reply to
Franc Zabkar

He might also find that it's not only the caps which have popped, too.

Bob

Reply to
Bob Parker

Why doesn't it make any sense? Surely all sorts of equipment has caps in it that are lower voltage than the input voltage. My desktop PC runs off 240V but has 6.3 volt caps. Obviously something has to step the voltage down but something similar could be happening with this board. The board provides 5V out for the HDD and CD and must provide lower voltages for the CPU etc.

I could just hang them off the board a little :-)

Michael

Reply to
Michael C

On Sat, 8 Dec 2007 22:57:18 +1100, "Michael C" put finger to keyboard and composed:

If the board has 10V caps, then it was designed so that these particular caps would not see more than 10V. I suspect they are probably sitting on a +5V rail. It would be quite easy to perform a continuity test with a multimeter (with power disconnected). Are the capacitors' positive terminals connected to the +12V input or the +5V output? Is there are short circuit between the +12V input and the +5V output ???

With power removed, test for continuity between the power pins at the board's PCI slots and the various supply rails and/or capacitors.

PCI bus pinout:

formatting link

- Franc Zabkar

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Reply to
Franc Zabkar

Makes sense.

You are correct. I just tested them and they are at 4.95V.

There doesn't appear to be.

They all seem to be ok except for the -12V is zero. I suspect that might be by design for this board.

The board is still running fine, I'll just replace these caps and see if they pop again. Maybe I touched the wrong thing as it was on the bench at the time.

Michael

Reply to
Michael C

Can't say I've ever accidentally exploded and decent sized electrolytics, although I have managed to put a few smaller caps in circuit arse about. One thing that does come to mind however re. exploding caps, is when i was at TAFE and some bright spark decided to drop an electrolytic cap in the solder pot. Luckily it was close to lunch time and everyone had left the room before the cap went bang and showered the room with molten solder.

James

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James

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Suzy

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