Since this game is "convertible " to add-a-ball, has that adjustment been made? Or is it awarding game credit for high score?

I figured it had been. If you set it to award a credit, does that work? That might help narrow down which path the trouble is on.

If it's set for free play that shouldn't affect the game awarding a credit. If you have credit at zero and the switch adjusted for free play it will still clock a game on it when you are awarded one. If it is awarding a credit that would tell you that it works and if you change the pin to extra ball it should award it(you said you did change the pin correct?). I have no clue why it wouldn't though...so no help there. If you need me to look at anything for comparison on my game let me know.

The setting you are referring to is only relevant for the on playfield special. So if set to extra ball it will provide an extra ball if you hit that special target when lit.

Making point thresholds will continue to award free games.

Also, keep in mind that Gottlieb EM games limit extra balls to one per ball in play. So if you get the special and the extra ball both lit on the playfield hitting the second target will not award an extra ball if hitting the first target already did so.

Gottlieb multiplayer games were never convertible to full add a ball play where the option existed. You only get full add a ball with a game that was configured as add a ball to begin with.

Not sure I'm reading you right but Jet Spin/Super Spin award extra ball for points as well as playfield feature. In other words, you get 100,000 or whatever your setting is, same player shoots again lights up---without hitting a lit special playfield feature. You can't get more than 1 extra ball at a time obviously but you CAN get it on points alone.

Maybe OP was confusing terminology or trying to get more than one?

Glass off, hit a single playfield feature repeatedly for points and see if same player shoots again lights up at some point(don't use a "special" feature obviously).

My opinion comes from looking at the instruction cards and the setting adjustment on the schematic for "credit" vs "extra ball".

Gottlieb_Jet_Spin_instruction_cards.pdf

Oooooo....K. Just so we are clear on diagnosing the issue though, you CAN get extra ball from points. My info comes from playing the game in my basement. So, that is what we are trying to troubleshoot. Regardless, I still don't have a solution.

Well, you learn something new every day. Looking at the flyer it says convertible to add a ball. Thats the first Gottlieb EM I've seen with that feature.

If its like 3/5 ball adjustment there will be a separate small connector for it. Could be on the bottom of the playfield, on the main relay board or on the head relay board.

On the schematic posted above, looks like a setting for Liberal or Conservative 'Extra Ball Frequency Adj.'