Quoted from vipe155:
I have a couple of System 80 displays where the backing tape/adhesive holding the glass to the circuit board has given up (maybe dried out?). Any suggestions on what to buy to stick the glass back on?
After cleaning off the old glue and tape residue with denatured alcohol, I just use a dime-size glob of clear silicone adhesive under the top two corners. It sticks well but can still be popped loose if ever needed. The main advantage is that it keeps a small gap behind the glass while still making really good contact over a potentially uneven, rough, or warped surface, and you have quite a bit of time to adjust position if needed before it sets up.
With tape, I always worry about failure with age, heat, or not making enough initial contact. And if the tape is too good (I actually have some that sticks as well as super-glue) you're never removing that display without breaking the PCB or the glass.
FWIW, I have original display boards with serial numbers that match my game, and with the silicone method, over the years I have been able to replace the glass tubes as needed without trouble.