Blown capacitor on evassemble bms

[flexy]

I have been attempting to build 72v headway pack and bought the 24 cell BMS from evassemble.
I neglected to connected battery negative to the BMS when I started connecting the monitoring leads to the each cell, there was a bit of smoke and it looks like one of the caps has blown .

The BMS has three layers of PCB so I separated them to see if I could replace it. The entire board and components are buried in a thick red resin, is there anyway to remove this resin so I can get at the blown cap and replace it?

 

[heathyoung]

Unfortunatly not - this stuff is almost impossible to remove non-destructively to the components underneath. I'm not sure if they do it to keep reverse-engineering difficult or for heat dissipation, but its evil stuff.

 

[amberwolf]

I don't have one to test it with, but I have removed potting epoxy from high-voltage laser power supply bricks using brake fluid a few times.

There may be other things that will dissolve it, too (or instead), depending on what kind of resin it is. You may have to experiment on a part of the board that doesn't appear to have anything critical underneath it, as you need a solvent that takes apart the sealing resin but NOT the resin/epoxy plastic of the components themselves.

 

[flexy]

Thanks for the advice guys , I shall experiment with various solvents I have, if not I guess it's a new board.

 

[heathyoung]

Good luck, i've never tried brake fluid on epoxy. I've got some old HeNe bricks that have had internal arc-overs that I might try this on. Found that petrol works well on RTV though

 

[amberwolf]

Just don't leave it in the brake fluid too long, or it will dissolve not only the potting compound but also the transistor epoxy.

 

[bigmoose]

Epoxy solvent: dimethylformamide (DMF) about $100/liter from Cole Palmer. This stuff is TOXIC and a possible carcinogen, though EPA does not rate it as a cancer risk. This solvent must be used with extreme respect. Personal protective equipment and a vent hood.

A diluted version is sold under the name "ATTACK" for lapidary use. (Making jewelry) there is some on eBay currently http://cgi.ebay.com/Attack-Solvent-Remove-Epoxy-/380266083549?pt=LH_DefaultDomain_0&hash=item58899ff4dd $13 bucks for 8 ounces.

Remember this stuff WILL FRY your liver and kidneys. Don't use it if you don't know how to use it properly! MSDS here: http://www.hisglassworks.com/files/attackmsds.pdf