The video said not available, so I'm not sure what pic you
could use. I can't get to the Neptune at the moment, but
here's a pic of the inside of a Neptune's cab that I took a
while back. I'm sure others will help, but if needed, I should
be able to get to a Neptune this weekend.. (T)

IMG_0596 (resized).JPG

ok first your pic

0111181946a_zpsg2pwjoro (resized).jpg

Now mine, I have a non insulated wire running from the last tab on A level to the 2nd to last tab on the C level. looks to be the same as your yellow

20180116_193014_resized (resized).jpg

As to the empty tab on the B level, I have a red&black molted wire attached but its also bridged to a contact on the A stack. Maybe the bridge to the A stack has come off for B tab? I can see the red and black lead in your pic, not sure where its attached

20180116_202108_resized (resized).jpg

When I owned a Neptune, the Series Relay (Q) was missing a sand resistor and my rollover scoring was messed up. I took photos of my friend's game and was able to install the missing resistor, which fixed scoring. Another Neptune owner here on Pinside was missing their Q relay, too.

https://pinside.com/pinball/forum/topic/neptune-chimes-not-working-all-the-time#post-1888242

My hunch is this resistor was prone to failure and an uncommon part, so repair people used creative workarounds instead of doing the right thing.

How does your Q relay look?

Im not getting redirected to the youtube video's.... but putting my Neptune in AAB mode (I normally leave it in Novelty mode) (two jones plugs to move).
Then each lane scores 500 pts. "three ball" mode. I didnt try 5 ball to see if the lane scoring is different. If it is this may be your source of trouble, ie the 3-5 ball jones plug.

All lanes are supposes to give 500 points in AAB mode. The other video you saw on YouTube is for the eBay listing of the game I bought five years ago. After owning it for a while, I noticed the scoring was incorrect and did not match the instruction cards. I had to install a sand resistor on the Q relay to get the rollovers functioning correctly.

This sand resistor is also crucial to correct operation of the WOW circuit on this game. Have you looked at your Q relay?

I've heard a number of times over the years that there was a production error during the run of "Neptune". There was some kind of issue that resulted in some of the games keeping the "WOW" lit for prolonged periods, thus making the game really easy to beat. I'm not sure of the particulars, but I think it did have something to do with the sand resistor in the "WOW" circuit. I'll ask Steve Young if he knows anything about it, and will post any insight he may have on this matter.

Years back when I was still very fresh into the hobby, I picked up a Neptune (didn't have a clue it
was a low production game) and after going through it, it played, but I remember something
was not right about the lighting. I showed the schematics to an old time Vender's mechanic, and
he said "this isn't right!", and although I wasn't yet 100% comfortable on reading schematics, something
seemed wrong to me also. The machine appearantly was wired to the incorrect schematics. I can't
remember the exact issue, or the exact fix, but do remember doing just a small amount of wire
rearranging, fixed the problem. It was an easy fix, but took awhile to track. Not sure if this was/is
related to the above problem, but for sure was wired incorrectly from the factory..

If all lanes are awarding a WOW, check your Q relay.

https://pinside.com/pinball/forum/topic/neptune-chimes-not-working-all-the-time#post-1887712