TDS460 Backplane Corrosion

[mcarberry]

I bought a TDS 460 a while ago non-working and took it home to found that it actually booted and occasionally passed all self-tests. However, it was flakey and I finally got around to taking it apart and figuring out what was wrong with it.

There were no obvious signs of leaking caps or corrosion until I got to the backplane, where it appeared that all Marcon brand capacitors on it had given up the ghost. I removed all the parts on the board in the affected area and cleaned as much as I could with alcohol.



As I cleaned, a significant amount of the solder resist came up and I can see in the area around C10, C11 and C7 where it looks like the corrosion is under the solder resist.

I was planning to clean this and then cover the copper with an epoxy like this (https://www.digikey.com/product-detail/en/chemtronics/CW2500/CW2500-ND/1929217). Is this a good plan? Should I remove more of the solder resist around those capacitors before doing this?

Thanks in advance!

[T3sl4co1l]

Hmm, make sure it's well cleaned (soak in water, alcohol), don't want that electrolyte going any farther.  Chip away at the edges of the corroded areas to be sure you're just scraping at clean soldermask.  I don't know about that epoxy specifically, but something to coat it is a good idea.  If nothing else, tin it, and cover anything that needs to be covered with tape or lacquer; or use an epoxy like that.

I had to replace all the little caps (on CPU, ACQ and HMI) in mine.  Didn't notice any damage on the backplane, but it looks like I should expect needing to dig into it at some point...

Tim

[xwarp]

Hit local drug store/walmart and buy some cheap fingernail polish.