on my machine, Joker Poker, there isn't a diode in the bottom of the cabinet that is in circuit with the tilt bob. The only one is the one under the PF that is also in circuit with the under playfield tilt.
https://pinside.com/pinball/forum/topic/home-for-the-gottlieb-sys1-sys-80b-guys-yep-i-guess-it-a-club/page/73#post-5638843
here is were i posted the pics of mine a few months ago.