[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

[Jeff Liebermann]

On Tue, 3 Nov 2009 21:55:21 -0500, "Chris"
wrote:

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?

Epoxy. G10/FR4 boards are made from fiberglass matting and epoxy
binder. If your PCB is made from phenolic instead of epoxy, use epoxy
anyway. Scrape out the carbonized material. Place some PTFE tape on
one side of the hole. Hold it in place with a mess of sticky tape and
maybe a temporary cardboard stiffener. The idea is that the epoxy
will not stick to the PTFE tape. Mix some "2hr" epoxy (not the 5 min
variety) and smear it into the hole. When set, remove the tape. Let
cure for at least 24 hrs before applying power.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[baron]

Meat Plow Inscribed thus:

On Tue, 3 Nov 2009 21:55:21 -0500, "Chris"
wrote:

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

How do you get carbon arcs on a low voltage door chime board?

From the open contact points spark/arc. Though I would have thought
that it could be cleaned off.

--
Best Regards:
Baron.

[PeterD]

On Tue, 3 Nov 2009 21:55:21 -0500, "Chris"
wrote:

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

This doesn't sound right, you can't arc with 24 volts. But, if it fact
it has happened, I'd recommend using a dremel to grind out the bad
parts of the board, and spray with a insulating coating, or even
fingernail polish.

[Michael A. Terrell]

PeterD wrote:

On Tue, 3 Nov 2009 21:55:21 -0500, "Chris"
wrote:

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

This doesn't sound right, you can't arc with 24 volts.


Yes you can, but the gap is quite narrow. I've seen sustained arcs at
5 volts on new PC boards when the board house damaged the negatives we
supplied. That narrowed the gap on the +5 volt rail and ground buss.
You had to look under a microscope to see it, but the +5 volt current
would go way up when the arc started. When we checked the remaining raw
boards the entire production run had the same defect. There wasn't
enough time to have a new batch made so the boards were hand trimmed
with an Exacto knife to remove the inch long strip of excess copper.
We had them return the negatives, and it was obvious they had been
mishandled. A lot of scratches had been touched up, but several layers
were so bad that we had a new set made before sending the work to a
different company.


But, if it fact
it has happened, I'd recommend using a dremel to grind out the bad
parts of the board, and spray with a insulating coating, or even
fingernail polish.


As long as it isn't a multi layerboard. If it is, you can cut right
through the next layer. I prefer the Exacto knife, for better control.


--
The movie 'Deliverance' isn't a documentary!

[Chris]

"Meat Plow" wrote in message
...
On Tue, 3 Nov 2009 21:55:21 -0500, "Chris"
wrote:

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

How do you get carbon arcs on a low voltage door chime board?


The carbon builds up then it arcs across. If you are thinking that low
voltage will not arc, you are mistaken. Take a 9volt battery and put steel
wool across both contacts. It will cause a fire. My kids use to love doing
this at the kitchen table when they were young.


Chris

[Chris]

"PeterD" wrote in message
...
On Tue, 3 Nov 2009 21:55:21 -0500, "Chris"
wrote:

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

This doesn't sound right, you can't arc with 24 volts. But, if it fact
it has happened, I'd recommend using a dremel to grind out the bad
parts of the board, and spray with a insulating coating, or even
fingernail polish.


You can arc with 24 volts. That is like saying a car battery will not arc.
It happens quite often.

Chris

[GregS[_3_]]

In article , "Chris" wrote:
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


I scrape out the black manually or with a Dremel tool.
I then coat the bad part with nail polish with a couple coats.
You could use epoxy if there needs more support.
Mesure the resistance across the arc points to
get an idea of the problem first.

greg