Burnt Board -- WWYD?

[tbonuss]

I've got a Spectra 212-T with a bad burn section. I already know whats wrong and how to fix, but I'm wondering if there is a typical approach to the burnt surface. I think i can just sever any existing traces and handwire, but should I treat the board in any way for longer term reliability?

Thanks in advance,

Steve

[nickb]

It looks like it's been reinforced in the past with some additional tinned copper wire. As the board seems to be still intact I'd just do more of the same, perhaps with a little tidy up.

[drewl]

You have to remove all that burnt carbon residue as it is conductive.

Scrape it all away with an exacto-knife, a file works well also.

Measure the area for resistance/shorts and make sure any nearby components aren't conducting where they shouldn't be.

[Jon Snell]

You have to remove all that burnt carbon residue as it is conductive.

Scrape it all away with an exacto-knife, a file works well also.

Measure the area for resistance/shorts and make sure any nearby components aren't conducting where they shouldn't be.

Use a fibre glass pen. It removes the residue and leaves the copper behind unless badly burned. Better than digging holes!
I would clean off the flux from the board after you have completed the repair, doesn't look good.

[bsco]

Use a fibre glass pen. It removes the residue and leaves the copper behind unless badly burned. Better than digging holes!
I would clean off the flux from the board after you have completed the repair, doesn't look good.

Right on. I have a couple of those pens...they are great to use and do an excellent job....just make sure that you don't get any fibers in your fingers....very painful....use a pair of gloves if needed....

[J M Fahey]

What a WEIRD solder mask

Wildly off center in most pads but not all, WTF?

Delights of hand taped artwork, clearly they had a silkscreen registration problem.

[drewl]

Right on. I have a couple of those pens...they are great to use and do an excellent job....just make sure that you don't get any fibers in your fingers....very painful....use a pair of gloves if needed....

Is that what those are?

We have some at work.

Also have the green insulation goop that comes in a pen.

[bsco]

Is that what those are?

We have some at work.

Also have the green insulation goop that comes in a pen.

I haven't seen the green insulation goop that you speak of but those pens are great for cleaning up corroded and tarnished surfaces...I use mine all the time and you can purchase refills for them as well......approx 10 in a pk....

[tbonuss]

Thanks folks. I still don't see how to do nested responses, so rather than not responding until I figure that out...

Thanks NickB and Drewl. Will clean it up. Weirdest thing = it works just fine as is. That is, all the resistances between components are as they should be (0 or infinite), so just out of curiosity, I stuffed the right zeners in there and now it puts out the proper voltage. It just seems impossible. No matter, no way can I put it back like that.

Thanks Jon Snell and BSCO. I'll order one of those as fiberglass pens as soon as I log off here, I was going to use the green goop that Drewl mentioned. I find that to be a really effective product for insulating in certain situations.

JMFahey: but I'm not even wearing a mask! ;}... Yeah, its a JMF Electronics (pre Dean Markley I guess) amp. It was utterly confusing trying to trace the schematic from the top visually--for example, multiple components seemed to be on a single pad that shouldn't, based on the schematic (which is partially illegible anyhow....) When I pulled it off, I realized why it didn't make sense from the top-read. I don't know anything about making PCB's, but it looks way off.

[bsco]

I have a can of conformal coating which I use to insulate any boards that have that kind of damage....if the damage is too much, I grind out all the cabonized board, square it up somewhat and cut another piece of ckt. board and epoxy it in place and clamp it overnight...then drill holes where they need to go, run some traces and re--install the parts...more work but depending on what you are working on it might be worth the trouble....just a thought.....

[Kevina]

Back in the day, we would cut away the damaged portion and epoxy glue in a piece of glass fibre (or paxolin). Once the glue was set, the required holes would be drilled, the components replaced, and the tracks relayed with tinned copper wire. Later, Pace brought out PCB track repair kits, which were brilliant. No idea if they are still available, I have ben retired fo some time now.

[drewl]

I have a can of conformal coating which I use to insulate any boards that have that kind of damage....if the damage is too much, I grind out all the cabonized board, square it up somewhat and cut another piece of ckt. board and epoxy it in place and clamp it overnight...then drill holes where they need to go, run some traces and re--install the parts...more work but depending on what you are working on it might be worth the trouble....just a thought.....

Yeah, we have cans of conformal coating also.

Going back to the 80's we used it on aircraft parts and more recently stuff that is exposed to the elements.

[bsco]

Back in the day, we would cut away the damaged portion and epoxy glue in a piece of glass fibre (or paxolin). Once the glue was set, the required holes would be drilled, the components replaced, and the tracks relayed with tinned copper wire. Later, Pace brought out PCB track repair kits, which were brilliant. No idea if they are still available, I have ben retired fo some time now.

We had the Pace equip also and used the track kit many times to fix up boards...wealso had the funnelets and tools to insert them as well.....

[tbonuss]

So, I went to just rebuild the section on perfboard...this is wrong, right? Maybe I'm just confused...

[DrGonz78]

If it works now, how could it be wrong?