Having watched Mike's teardown of the Leica with fascination I remembered I tore down one of these Melles Griot HeNe lasers like 5 years back.
The actual laser tube is fitted in an aluminium tube with some thermoplastic gooey. Getting the tube out therefore involved sticking the whole thing in the kitchen oven (..I wasn't married at the time
..) to melt it down. Bit of a stink but he..
The whole procedure is documented in fotos and videos at
https://wkb.home.xs4all.nl/Laser-hacking/The videos show the defective tube. I was told by a laser guru (the author of the LaserFAQ btw) that the tube exhibits heavy sputtering which is the reason it never starts.