Burnt board repair with fibreglass

[Steevsee]

I bought three wrecked WMS driver boards from ebay.  The worst one had a hole burnt right through it, from an overheated transistor.
This was a bit of an experiment, to see if I could salvage this damaged board.

After removing all the components from the area, I used a small file to remove as much charred material as I could and also trimmed back the fibre matting which is inside the board.

It's a bit hard to tell from the pics , but the right angled trace is actually "floating" over the void and I was very careful to avoid breaking this.
The large ground trace is also partly "floating" especially around the existing repair.

After gently cleaning the area with Isopro alcohol and an old toothbrush, I covered the hole with sticky tape first and then a piece of an old credit card held in place with more sticky tape.

Please click on the images to view full size.

[Strangeways]

I will be keenly following this process. I have a couple of boards in similar condition.

[Steevsee]

Next I cut some small pieces of the fibreglass sheet from the repair kit and worked these into place as best I could to fill the hole.

When I mixed up the resin and hardener, I added a small amount of green acrylic paint to try to match the board colour.
Turned out just 'ok' as it's pretty hit and miss, since you don't have too much time to stuff around adding more paint and I wasn't  really sure if the paint would react with the resin.

Started to drip/pour the resin into the hole and onto the new fibreglass matting. 
You need to press the resin down into the matting, so that it soaks in and removes any air bubbles.

I was also careful not to let any resin get into and block the through holes. I used an old resister to clear the holes if any did get in.

The last pic shows about halfway done pouring the resin.

[Steevsee]

These pics show the end result after totally filling the hole with resin and then a quick sand to remove the rough edges, once the fibreglass had hardened. 

I used a small file and a screw driver to press down that loose trace as the resin was hardening, so that I could sand back the fibreglass without totally destroying this trace.

The credit card piece and sticky tape came away easily once the resin had hardened a little, and left a nice smooth fill.

I re-drilled the two missing holes for the transistor.
(Note the special increased spacing and wobbly allignment of these holes...er, to aid with heat dissapation     )

I needed to clean up a couple of the solder pads that had resin partly covering them but this was fairly easy to scrape off.

Anyway I'm pretty pleased with how it turned out and hopefully I can remount the transistor easily now.

I haven't actually tried soldering to this area yet but will let you know how it goes in the next couple of days.

[Steevsee]

UPDATE

Re-populated the board around the damaged area. 

Repair seems strong and handled the soldering process without any apparent problems.

[ajlaird]

Now that is keen!

Great work, you might just inspire some other people to do the same!!

[ktm450]

Nice work 

[Retropin]

Awesome stuff and great thinking... I er.... especially like the.. er... heat dissipation idea..LOL

[Skybeaux]

Excellent work

[carnut]

youre a very clever boy steve!
no doubt about it!

[63wizz]

would the resin without the fiber  matting work ok, i have a few burnt boards aswell.

Ian

[Olivia_jason]

would the resin without the fiber  matting work ok, i have a few burnt boards aswell.

Ian

no the resin wouldn't work on its own, it would need some strength as when resin reacts with catylist it gets hot and will shrink and crack wont have any strength on its own. esp if its polyester resin

[Steevsee]

would the resin without the fiber  matting work ok, i have a few burnt boards aswell.

Ian

If you want/need some matting just let me know, as I have heaps left over.

Happy to post some to you.

[Steevsee]

Just a quick update on this board.

I'm keen to test out the repair but need to sort a few other issues first.

There were a couple of transistors missing/damaged on the board as well as an obviously broken capacitor, so all of these were replaced.

Next I removed the existing sockets for the PIA chips as they looked a little worse for wear.  The solder pads were all cleaned and sanded lightly.

The 40 pin interconnect header was the next to go.  These things are a real pain to remove! 
First I cut and removed the plastic surrounds piece by piece, before desoldering and removing the pins individually.

The last picture shows close up, exactly why these connectors must be replaced.

[Steevsee]

All the pins are finally removed before the pads are cleaned of solder and lightly sanded .

Be aware that the two holes on each end require additional heat/time to desolder due to the large solder pad area here.