Wow, long dead thread 
I’m gonna be of little help on this now - last weekend I finally tossed my K40 in the trash. Between a 60W Redsail and a 45W Glowforge I hadn’t used the K40 in a couple of years so I finally just tossed it to make room for a new CNC plasma cutter. I did find a new (well probably a year or so old) 40W tube I had bought as a potential replacement for the K40 if anyone is in the market for one.
yeah like i said i shelved it ,how much for the tube what brand is it if i could just get the machine to perform reasonably well that would be a start