Circuit Board Sparking

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  #1  
Old 03-29-14, 11:16 AM
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Circuit Board Sparking

Hi,
I have a light above my oven, with an extractor fan.

I switched it on yesterday and it worked fine, until the light started flicking and then went off.

It uses two light bulbs and states: "MAX 40W".

I have put two new 15w bulbs in to no avail, so I took the switch box a part.

The light switch, underneath, one of the pins that was originally soldered is all black and burnt. I have tried putting a tiny amount of foil over the burn, and it works for a few seconds, sparks and burns, and then stops working.

Can anyone explain what I need to do in layman's terms to fix it.

Thanks
Dan

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  #2  
Old 03-29-14, 11:24 AM
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I'm guessing, but it looks like a bad solder connection from the start. A poor connection will result in heat and ultimately a burn spot as shown. The foil attempt would be a fire hazard. What could be tried would be to clean the surfaces and resolder the connection, however, that should be done by some who knows how to solder. Done wrong and again it becomes a fire hazard.

Find some with a soldering iron who know how to use it and it would be a simple job.

Bud
 
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Old 03-29-14, 12:27 PM
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It's a common problem with the old pinball machines I work on. Over time the solder joint mechanically fails, cracking with causes an intermittent connection, arcing and eventually failure. It's a pretty simple fix if of re-soldering if caught early enough that the trace on the circuit board is still good.
 
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Old 03-29-14, 01:18 PM
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Thank you for the replies. I thought as much.

My dad has a soldering iron so I will get him to do it.

Just a question, what is that burnt switch actually connected to, because the track does't seem to run anywhere... So I guessed that the solder just held the pin in place.

Thanks
Dan
 
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Old 03-29-14, 04:31 PM
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It's connected to the brown wire, right by the "VR" mark.. The power (common) inlet goes to the pin on the other side of the switch, and it comes out that pin, follows the trace to the brown wire - which I assume goes to the light sockets.
 
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Old 03-29-14, 05:05 PM
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You can solder jumper wires around the damaged sections of foil. Snip off any loose foil that is not reinforced by solder with an embedded wire.

Ordinary electronic solder will not stick to aluminum or aluminum foil. Do not use plumbing solder (requires higher heat that can damage components) or paste (the residue will slowly eat through the connection).

It looks to me as if some of the foil traces have a layer of solder over them while others do not. I am guessing that the solder covered traces need to carry more current.
 
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Old 04-01-14, 06:09 AM
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Thanks for the replies people. I cleaned the burnt connection the best I could and then re-soldered it. The light is working great now.

Thanks again.
 
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Old 04-01-14, 11:57 PM
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Great news

If you have that type of problem in the future...... clean the board with rubbing or isopropyl alcohol and an old toothbrush. It will remove all the carbon.
 
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