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Abe D
Guest

Sun Feb 02, 2020 9:45 am   



I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections. In a pinch, I have
glued the broken parts back together with JB Quick Weld. After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components. Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?). I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe

micky
Guest

Sun Feb 02, 2020 9:45 am   



In sci.electronics.repair, on Sun, 2 Feb 2020 02:47:18 -0500, Abe D
<abednpspam_at_verizon.net> wrote:

Quote:
I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections. In a pinch, I have
glued the broken parts back together with JB Quick Weld. After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components.


Sounds good.

Quote:
Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?).


I'm no pro, but why not the same thing. Does it matter if the edges of
the screen are touching if the screen itself is all connected to itself.
Then you can see if the thing it comes from works or not.

40 years ago I had a roommmate whose father threw a clock-tv at him. I
neve saw another one. So cute. 9" TV, I would have liked to have had
one. Board was broken in about 20 places but it worked after I jumpered
each of them.

Quote:
I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe


John-Del
Guest

Sun Feb 02, 2020 2:45 pm   



On Sunday, February 2, 2020 at 2:47:22 AM UTC-5, Abe D wrote:
Quote:
I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections. In a pinch, I have
glued the broken parts back together with JB Quick Weld. After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components. Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?). I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe


It's too late now but repairing board with a topical coating of epoxy is not the way to stabilize it. The epoxy acts like a top hinge and the bottom of the board will flex away from the crack. To make it more stable, you have to add some epoxy on the other side and hope it adheres.

The proper way to repair a fractured board is to remove any component(s) that crosses the break, and fit the board pieces back together where the seam doesn't even show. You may actually have to break the board a bit more to get it to fit perfectly.

At this point, apply FRESH cyanoacrylate so it wicks inside the fracture and bonds the board completely together from the inside, not just one side.

If done properly, the cracks will be barely visible. Scrape the green mask off the trace just at the break and half the distance the trace is wide. A drop of solder across each land will finish it.

In your case, because the pieces don't fit that well, scrape back the mask and hand wire from point to point and across the fracture with some fine copper stranded wire (one or more strands depending on width of the trace), and coat the entire trace with solder using the copper strand as a sort of "rebar".

Deflux the board and apply either a conformal coating or get some green nail polish to protect the lands.

Abe D
Guest

Sun Feb 02, 2020 6:44 pm   



On 2/2/20 8:32 AM, John-Del wrote:
Quote:
On Sunday, February 2, 2020 at 2:47:22 AM UTC-5, Abe D wrote:
I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections. In a pinch, I have
glued the broken parts back together with JB Quick Weld. After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components. Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?). I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe

It's too late now but repairing board with a topical coating of epoxy is not the way to stabilize it. The epoxy acts like a top hinge and the bottom of the board will flex away from the crack. To make it more stable, you have to add some epoxy on the other side and hope it adheres.

The proper way to repair a fractured board is to remove any component(s) that crosses the break, and fit the board pieces back together where the seam doesn't even show. You may actually have to break the board a bit more to get it to fit perfectly.

At this point, apply FRESH cyanoacrylate so it wicks inside the fracture and bonds the board completely together from the inside, not just one side.


Not totally clear to me here. Am I going to try applying more epoxy on
the board side of the crack, cyanoacrylate, or both?

Quote:

If done properly, the cracks will be barely visible. Scrape the green mask off the trace just at the break and half the distance the trace is wide. A drop of solder across each land will finish it.


What about the large, outer section of the board appearing more like a
screen rather than solid trace? I doubt I could find stranded wire wide
enough and pretty fragile there to try scraping. Also, what's the best
tool for the scraping?

Quote:

In your case, because the pieces don't fit that well, scrape back the mask and hand wire from point to point and across the fracture with some fine copper stranded wire (one or more strands depending on width of the trace), and coat the entire trace with solder using the copper strand as a sort of "rebar".

Deflux the board and apply either a conformal coating or get some green nail polish to protect the lands.


Nail polish would be a go, but what to use for defluxing?

Thanks.


Guest

Sun Feb 02, 2020 6:45 pm   



On Sun, 2 Feb 2020 02:47:18 -0500, Abe D <abednpspam_at_verizon.net>
wrote:

Quote:
I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections. In a pinch, I have
glued the broken parts back together with JB Quick Weld. After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components. Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?). I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe

I think some JB weld formulations have very fine metal powder in them
for strength. Maybe you should see if the stuff you used is conductive
before you apply power to the board again.
Eric

Ralph Mowery
Guest

Sun Feb 02, 2020 6:45 pm   



In article <r16ua5$7ce$1_at_dont-email.me>, abednpspam_at_verizon.net says...
Quote:

In your case, because the pieces don't fit that well, scrape back the mask and hand wire from point to point and across the fracture with some fine copper stranded wire (one or more strands depending on width of the trace), and coat the entire trace with solder using the copper strand as a sort of "rebar".

Deflux the board and apply either a conformal coating or get some green nail polish to protect the lands.

Nail polish would be a go, but what to use for defluxing?



Depends on the flux used.

Most of the time use IPA . That is alcohol that is 90% or better with
no addatives that is often in common rubbing alcohol.

The common rubbing alcohol that is 70 % would be ok except most of it
contains other chemicals that leave a residue on the boards.

John-Del
Guest

Sun Feb 02, 2020 7:45 pm   



On Sunday, February 2, 2020 at 11:44:57 AM UTC-5, Abe D wrote:
Quote:
On 2/2/20 8:32 AM, John-Del wrote:
On Sunday, February 2, 2020 at 2:47:22 AM UTC-5, Abe D wrote:
I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections. In a pinch, I have
glued the broken parts back together with JB Quick Weld. After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components. Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?). I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe

It's too late now but repairing board with a topical coating of epoxy is not the way to stabilize it. The epoxy acts like a top hinge and the bottom of the board will flex away from the crack. To make it more stable, you have to add some epoxy on the other side and hope it adheres.

The proper way to repair a fractured board is to remove any component(s) that crosses the break, and fit the board pieces back together where the seam doesn't even show. You may actually have to break the board a bit more to get it to fit perfectly.

At this point, apply FRESH cyanoacrylate so it wicks inside the fracture and bonds the board completely together from the inside, not just one side.

Not totally clear to me here. Am I going to try applying more epoxy on
the board side of the crack, cyanoacrylate, or both?


I had two avenues of advice: the first how to properly repair a cracked or totally broken PC so it's virtually invisible, and advice directed to you having already attempted a repair with epoxy.

Because you have already epoxied the board together, it's really too late to use the cyano adhesive, particularly if you put epoxy into the crack. We never want to use cyano as a filler. The beauty of cyanoacrylate is that it doesn't require a gap in order to put the epoxy in. With cyano, you can fit the board together perfecly and the cyano will wet *into* the PC (either glass or phenolic) and bond it with no gap whatsoever. Properly done, there is virtually no gap across the broken foil and the foil ends butt together almost perfectly.

If you can remove the epoxy you already put down, and there is no epoxy in the break line, then you can refit the pieces so the crack is perfectly joined and virtually invisible. At this point, you can use cyanoacrylate to permanently bond the board internally, as opposed to using external adhesive..

If done properly, no jumpers are even required as the mask can be scrapped off right at the crack and a dot of solder put across the gap. Because the board is bonded internally, there is is virtually no flex and the solder ball will make a perfectly clean and virtually indestructible connection across the break.

If you can't remove the epoxy, you're better off adding a layer to the bottom to reduce the "hinge" effect you will get with epoxy on one side or the other allowing flexing.

As for the large areas of damaged foil, you can add strips of solder wick braid to add some physical strength as well as complete the circuit.

Tempestinatesttube
Guest

Sun Feb 02, 2020 8:45 pm   



On 2/2/20 1:16 PM, John-Del wrote:
Quote:
On Sunday, February 2, 2020 at 11:44:57 AM UTC-5, Abe D wrote:
On 2/2/20 8:32 AM, John-Del wrote:
On Sunday, February 2, 2020 at 2:47:22 AM UTC-5, Abe D wrote:
I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections. In a pinch, I have
glued the broken parts back together with JB Quick Weld. After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components. Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?). I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe

It's too late now but repairing board with a topical coating of epoxy is not the way to stabilize it. The epoxy acts like a top hinge and the bottom of the board will flex away from the crack. To make it more stable, you have to add some epoxy on the other side and hope it adheres.

The proper way to repair a fractured board is to remove any component(s) that crosses the break, and fit the board pieces back together where the seam doesn't even show. You may actually have to break the board a bit more to get it to fit perfectly.

At this point, apply FRESH cyanoacrylate so it wicks inside the fracture and bonds the board completely together from the inside, not just one side.

Not totally clear to me here. Am I going to try applying more epoxy on
the board side of the crack, cyanoacrylate, or both?


I had two avenues of advice: the first how to properly repair a cracked or totally broken PC so it's virtually invisible, and advice directed to you having already attempted a repair with epoxy.

Because you have already epoxied the board together, it's really too late to use the cyano adhesive, particularly if you put epoxy into the crack. We never want to use cyano as a filler. The beauty of cyanoacrylate is that it doesn't require a gap in order to put the epoxy in. With cyano, you can fit the board together perfecly and the cyano will wet *into* the PC (either glass or phenolic) and bond it with no gap whatsoever. Properly done, there is virtually no gap across the broken foil and the foil ends butt together almost perfectly.

If you can remove the epoxy you already put down, and there is no epoxy in the break line, then you can refit the pieces so the crack is perfectly joined and virtually invisible. At this point, you can use cyanoacrylate to permanently bond the board internally, as opposed to using external adhesive.


Too well bonded now, even though not perfectly aligned. And I did use
some cyano on the board side just a little while ago to fill in. Not
the best idea for sure and it's only about 49 F in the room where the
board is, so I better wait a full day before doing anything else.

Quote:

If done properly, no jumpers are even required as the mask can be scrapped off right at the crack and a dot of solder put across the gap. Because the board is bonded internally, there is is virtually no flex and the solder ball will make a perfectly clean and virtually indestructible connection across the break.


The board rejoining is too imperfect for solder dots. Looks like I will
be using jumpers and solder braid, removing flux afterwards, and
covering with nail polish.


> If you can't remove the epoxy, you're better off adding a layer to the bottom to reduce the "hinge" effect you will get with epoxy on one side or the other allowing flexing.

I'm going to glue a couple of round wooden sticks along each length of
the board on the underside. There will be one horizontal stick along
each edge. This won't interfere when I reinstall the board. Hopefully
it will help augment any strengthening needed.



> As for the large areas of damaged foil, you can add strips of solder wick braid to add some physical strength as well as complete the circuit.

Solder braid, good idea. Don't have any though, will have to order
some. What's the best way to remove the conformal coating?

Tempestinatesttube
Guest

Sun Feb 02, 2020 8:45 pm   



On 2/2/20 12:32 PM, etpm_at_whidbey.com wrote:
Quote:
On Sun, 2 Feb 2020 02:47:18 -0500, Abe D <abednpspam_at_verizon.net
wrote:

I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections. In a pinch, I have
glued the broken parts back together with JB Quick Weld. After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components. Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?). I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe
I think some JB weld formulations have very fine metal powder in them
for strength. Maybe you should see if the stuff you used is conductive
before you apply power to the board again.
Eric


No conductivity, so thumbs up there. Thanks for pointing that out.
Would have hated to go through all this only to realize I was
shortchanged by the epoxy.

Tempestinatesttube
Guest

Sun Feb 02, 2020 8:45 pm   



On 2/2/20 12:06 PM, Ralph Mowery wrote:
Quote:
In article <r16ua5$7ce$1_at_dont-email.me>, abednpspam_at_verizon.net says...

In your case, because the pieces don't fit that well, scrape back the mask and hand wire from point to point and across the fracture with some fine copper stranded wire (one or more strands depending on width of the trace), and coat the entire trace with solder using the copper strand as a sort of "rebar".

Deflux the board and apply either a conformal coating or get some green nail polish to protect the lands.

Nail polish would be a go, but what to use for defluxing?



Depends on the flux used.

Most of the time use IPA . That is alcohol that is 90% or better with
no addatives that is often in common rubbing alcohol.

The common rubbing alcohol that is 70 % would be ok except most of it
contains other chemicals that leave a residue on the boards.


Have both 70 and 90, so thumbs up, thanks!

Tempestinatesttube
Guest

Sun Feb 02, 2020 8:45 pm   



On 2/2/20 2:35 PM, Tempestinatesttube wrote:
Quote:
On 2/2/20 12:06 PM, Ralph Mowery wrote:
In article <r16ua5$7ce$1_at_dont-email.me>, abednpspam_at_verizon.net says...

In your case, because the pieces don't fit that well, scrape back
the mask and hand wire from point to point and across the fracture
with some fine copper stranded wire (one or more strands depending
on width of the trace), and coat the entire trace with solder using
the copper strand as a sort of "rebar".

Deflux the board and apply either a conformal coating or get some
green nail polish to protect the lands.

Nail polish would be a go, but what to use for defluxing?



Depends on the flux used.

Most of the time use IPA .  That is alcohol that is 90% or better with
no addatives that is often in common rubbing alcohol.

The common rubbing alcohol that is 70 % would be ok except most of it
contains other chemicals that leave a residue on the boards.


Have both 70 and 90, so thumbs up, thanks!


Maybe not so thumbs up when I read more clearly. Standard ISO is all I
have. What about Everclear?


Guest

Sun Feb 02, 2020 9:45 pm   



On Sun, 2 Feb 2020 14:27:47 -0500, Tempestinatesttube
<tempest_at_ina.com> wrote:

Quote:
On 2/2/20 12:32 PM, etpm_at_whidbey.com wrote:
On Sun, 2 Feb 2020 02:47:18 -0500, Abe D <abednpspam_at_verizon.net
wrote:

I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections. In a pinch, I have
glued the broken parts back together with JB Quick Weld. After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components. Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?). I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe
I think some JB weld formulations have very fine metal powder in them
for strength. Maybe you should see if the stuff you used is conductive
before you apply power to the board again.
Eric

No conductivity, so thumbs up there. Thanks for pointing that out.
Would have hated to go through all this only to realize I was
shortchanged by the epoxy.

Yeah, that would suck.


John-Del
Guest

Sun Feb 02, 2020 10:45 pm   



On Sunday, February 2, 2020 at 1:58:34 PM UTC-5, Tempestinatesttube wrote:

Quote:
Solder braid, good idea. Don't have any though, will have to order
some. What's the best way to remove the conformal coating?


I just use a jeweler's screwdriver that's not knackered up. If it has a crisp edge, you can easily scrape off the conformal coating (if the board has it) as well as the green solder mask. Expose the copper and use a bit of flux to improve the wetting and bonding of the solder to the copper.

Tempestinatesttube
Guest

Sun Feb 02, 2020 10:45 pm   



On 2/2/20 4:06 PM, John-Del wrote:
Quote:
On Sunday, February 2, 2020 at 1:58:34 PM UTC-5, Tempestinatesttube wrote:

Solder braid, good idea. Don't have any though, will have to order
some. What's the best way to remove the conformal coating?

I just use a jeweler's screwdriver that's not knackered up. If it has a crisp edge, you can easily scrape off the conformal coating (if the board has it) as well as the green solder mask. Expose the copper and use a bit of flux to improve the wetting and bonding of the solder to the copper.


Very good, thanks again. Will tackle this tomorrow once I have the
braid in hand.

Tom Biasi
Guest

Mon Feb 03, 2020 3:45 am   



On 2/2/2020 11:44 AM, Abe D wrote:
Quote:
On 2/2/20 8:32 AM, John-Del wrote:
On Sunday, February 2, 2020 at 2:47:22 AM UTC-5, Abe D wrote:
I have a broken circuit board and accompanying topside components here:

https://imgur.com/a/Pbt1HSU

The red circled areas show the cracked sections.  In a pinch, I have
glued the broken parts back together with JB Quick Weld.  After several
hours, it seems stable enough to handle.

Now, the question is, what's the best way to rejoin the broken traces?
Initial thought was to just jumper over the solid sections and join the
jumpers between soldered components.  Not so sure what to do about the
large screened sections (probably serving as a ground screen for the
flyback topside?).  I welcome any tips or thoughts. If I start trying to
scrape the conformal coating, it may come apart again.

Unfortunately, the board cannot be replaced.

Thanks in advance.

Abe

It's too late now but repairing board with a topical coating of epoxy
is not the way to stabilize it.  The epoxy acts like a top hinge and
the bottom of the board will flex away from the crack.  To make it
more stable, you have to add some epoxy on the other side and hope it
adheres.

The proper way to repair a fractured board is to remove any
component(s) that crosses the break, and fit the board pieces back
together where the seam doesn't even show.  You may actually have to
break the board a bit more to get it to fit perfectly.

At this point, apply FRESH cyanoacrylate so it wicks inside the
fracture and bonds the board completely together from the inside, not
just one side.

Not totally clear to me here.  Am I going to try applying more epoxy on
the board side of the crack, cyanoacrylate, or both?


If done properly, the cracks will be barely visible.  Scrape the green
mask off the trace just at the break and half the distance the trace
is wide.  A drop of solder across each land will finish it.

What about the large, outer section of the board appearing more like a
screen rather than solid trace?  I doubt I could find stranded wire wide
enough and pretty fragile there to try scraping.  Also, what's the best
tool for the scraping?


In your case, because the pieces don't fit that well, scrape back the
mask and hand wire from point to point and across the fracture with
some fine copper stranded wire (one or more strands depending on width
of the trace), and coat the entire trace with solder using the copper
strand as a sort of "rebar".

Deflux the board and apply either a conformal coating or get some
green nail polish to protect the lands.

Nail polish would be a go, but what to use for defluxing?

Thanks.


JB weld is conductive.


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