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Circuit Board Arc Track Repair
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Chris  
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 More options Nov 4, 10:45 am
Newsgroups: sci.electronics.basics
From: "Chris" <newsgrou...@hotmail.com>
Date: Tue, 3 Nov 2009 21:45:09 -0500
Local: Wed, Nov 4 2009 10:45 am
Subject: Circuit Board Arc Track Repair
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I have a 55 year old door chime clock and the board has carbon arcs which is
causing a short. I have seen boards with this problem before and they were
repaired using some type of filler. What is used?

Thank you for your help

Chris


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Tom Biasi  
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 More options Nov 4, 8:57 pm
Newsgroups: sci.electronics.basics
From: "Tom Biasi" <tombi...@optonline.net>
Date: Wed, 4 Nov 2009 07:57:10 -0500
Local: Wed, Nov 4 2009 8:57 pm
Subject: Re: Circuit Board Arc Track Repair
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"Chris" <newsgrou...@hotmail.com> wrote in message

news:00aa0168$0$6726$c3e8da3@news.astraweb.com...
>I have a 55 year old door chime clock and the board has carbon arcs which
>is causing a short. I have seen boards with this problem before and they
>were repaired using some type of filler. What is used?

> Thank you for your help

> Chris

What is causing the arc?
Your description of the problem is a little confusing.

Tom


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Chris  
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 More options Nov 4, 9:07 pm
Newsgroups: sci.electronics.basics
From: "Chris" <newsgrou...@hotmail.com>
Date: Wed, 4 Nov 2009 08:07:47 -0500
Local: Wed, Nov 4 2009 9:07 pm
Subject: Re: Circuit Board Arc Track Repair
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"Tom Biasi" <tombi...@optonline.net> wrote in message

news:4af17a27$0$22529$607ed4bc@cv.net...

Over time the carbon builds up and causes the arc which puts small
gauge/hole in the board. This was a frequent problem of board of old. It
does not happen that much on new boards since they are made of a different
material now.

Chris


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default  
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 More options Nov 4, 10:03 pm
Newsgroups: sci.electronics.basics
From: default <defa...@defaulter.net>
Date: Wed, 04 Nov 2009 09:03:02 -0500
Local: Wed, Nov 4 2009 10:03 pm
Subject: Re: Circuit Board Arc Track Repair
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On Wed, 4 Nov 2009 08:07:47 -0500, "Chris" <newsgrou...@hotmail.com>
wrote:

I worked in a lab where the strike voltage of the deuterium lamps we
used would sometimes cause a poorly designed board to arc - then the
100 watt power supply would arc the board until there was a large hole
and the arc couldn't sustain itself.

We drilled out the portion that was burnt, leaving only clean
fiberglass epoxy around the edges, then put a piece of masking tape on
the trace side and fill the hole with epoxy- remove the tape after the
epoxy hardens  - and rewire the burned traces with point to point
wires.  Really large voids can be bridged with a few layers of
fiberglass window screen to add stiffness to the board if it needs
mechanical strength in the area that is repaired.
--


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Tom Biasi  
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 More options Nov 4, 10:44 pm
Newsgroups: sci.electronics.basics
From: "Tom Biasi" <tombi...@optonline.net>
Date: Wed, 4 Nov 2009 09:44:14 -0500
Local: Wed, Nov 4 2009 10:44 pm
Subject: Re: Circuit Board Arc Track Repair
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"default" <defa...@defaulter.net> wrote in message

news:qv13f5p99gfa73nnnnqu88vp22nrju2eid@4ax.com...

I agree with this procedure.

Tom


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Bob Eld  
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 More options Nov 5, 1:08 am
Newsgroups: sci.electronics.basics
From: "Bob Eld" <nsmontas...@yahoo.com>
Date: Wed, 4 Nov 2009 09:08:00 -0800
Subject: Re: Circuit Board Arc Track Repair
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"Chris" <newsgrou...@hotmail.com> wrote in message

news:00aa0168$0$6726$c3e8da3@news.astraweb.com...

> I have a 55 year old door chime clock and the board has carbon arcs which
is
> causing a short. I have seen boards with this problem before and they were
> repaired using some type of filler. What is used?

> Thank you for your help

> Chris

Drill out any carbonized areas to insure there are no carbon current paths
shorting anything. Re-wire any lost clad with copper wire soldering it in
place. There is usually no need to fill any voids unless there is an obvious
loss of strength or rigidity of the board. If you must fill the board, bondo
works well and is thick enough to stay in place while hardening. Some
epoxies work well too but it is usually not necessary to re-fill drilled out
areas. Air is actually a good insulator and provides longer creepage paths
than any re-fill patch does.

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default  
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 More options Nov 5, 2:07 am
Newsgroups: sci.electronics.basics
From: default <defa...@defaulter.net>
Date: Wed, 04 Nov 2009 13:07:12 -0500
Local: Thurs, Nov 5 2009 2:07 am
Subject: Re: Circuit Board Arc Track Repair
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On Wed, 4 Nov 2009 09:44:14 -0500, "Tom Biasi"

I used the same technique on a large front panel.  They wanted the
controllers and meters replaced with different ones and different
lights and switches.  Epoxied it all with masking tape, hit it with
some spray paint, re cut the holes and by the time it was finished the
modifications were only visible from the inside of the case.  Took
less time than making the drawings necessary to have some sheet metal
shop do the job for me.
--

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Clint Sharp  
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 More options Nov 5, 4:55 pm
Newsgroups: sci.electronics.basics
From: Clint Sharp <cl...@clintsmc.demon.co.uk>
Date: Thu, 5 Nov 2009 08:55:46 +0000
Local: Thurs, Nov 5 2009 4:55 pm
Subject: Re: Circuit Board Arc Track Repair
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In message <00aa0168$0$6726$c3e8...@news.astraweb.com>, Chris
<newsgrou...@hotmail.com> writes
>I have a 55 year old door chime clock and the board has carbon arcs
>which is causing a short. I have seen boards with this problem before
>and they were repaired using some type of filler. What is used?

Depends on the board type, if it's paxolin or some kind of resin bonded
paper then just scrap/grind out the carbonised parts (dremel with a burr
is ideal) then fill with the epoxy of your choice unless you're happy to
leave it as is. The only problem with not filling is you may increase
the moisture absorption of the board by exposing the edges, making
further damage more likely, conformal coating would help.

>Thank you for your help

>Chris

--
Clint Sharp

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