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This is part warning to others, part query...

My 2.x laser is almost complete, and I've been doing some test jobs to try things out. While cutting a piece of paper, I noticed some buzzing, and that the laser power was fluctuating. A moment later the positive connection to the tube was in flames and had popped off. I hit the emergency stop, and put it out with the fire extinguisher. Massive overkill (the flame was match sized), but I didn't want to get too close.

I think the problem was the self-amalgamating butyl rubber tape I used to cover the connections (from http://www.jaycar.com.au/productView.asp?ID=NM2826). While it is supposed to be for high voltages, and able to resist coronas, I found later that it's very easy to set alight! I had assumed that given the intended application it would include some flame retardant additives.

I'm going to try some silicone rescue tape instead, can anyone give suggestions on a particular brand fit for the application, or is the generic rescue tape good enough? Any extra tips on getting a secure, non-flammable connection (using a potting compound for instance to completely exclude air)?

I'm pretty sure this is in the 2.x instructions.

First I stripped the positive and negative supply wires back 2x the length of the stud on the laser.

Holding the stripped end parallel to the stud and flush with the end (extending past the tube, in the opposite direction of the final connection), I used a very fine tinned wire (one strand from a stripped stranded wire) wrapped around and around the stud and the supply wire. This makes a very tight connection.

Now you can bend the supply wire back the other way so it sticks out in the desired direction. I used a long piece of self-fusing silicone tape to go around the tube and cover the stud on both sides. Then I wrapped another piece around the stud to reinforce it.

Yes, that's pretty much exactly what I did, except I used self-amalgamating butyl rubber tape instead of silicone, which I presumed would be equally suited to high-voltage connections, however it has caused me trouble.

I used http://www.harborfreight.com/1-x-10-ft-self-bonding-super-tape-68401.html on mine and it has not shown any issue for a 8 months. The wire is connected to the laser tube wire stud with the metal part of http://www.radioshack.com/product/index.jsp?productId=2103986 removed from the plastic. You end up with a little metal tube with two set screws.

I used clear household silicone caulk and a short piece of silicone tubing to pot and reinforce the connections.

TLHarrell wrote:I used clear household silicone caulk and a short piece of silicone tubing to pot and reinforce the connections.

I would recommend against that. Silicone caulk contains acetic acid, that will corrode your connections over time.

There is neutral-cure silicone caulk too. The household version is sold for use on acid-sensitive stone (e.g. travertine, marble).

Try mine: http://www.lightobject.com/6X9-Silicon- ... -P756.aspx