since its so old and lacks modern safety and security features, like
light sensors on door so obstruction reverses door, and things like
rolling code technology to make it harder to break in by remote you may
be better off just replacing the opener. its not expensive and besides
if your ever going to sell such a old ppener is a home inspectors
friend.

old openers put lots of pressure on a obstruction before reversing way
more than current units, after kids were crushed.

sears has sales for 200 to 250 installed.

may be better investment than 50 bucks on a ancient unit