Circuit Board Arc Track Repair

[Chris]

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

 

[Tom Biasi]

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

 

[Chris]

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

Tom

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

 

[Tom Biasi]

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.
--

I agree with this procedure.

Tom

 

[Bob Eld]

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.

 

[Clint Sharp]

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.