I have a 1977 Gottlieb Jacks Open that recently came out of storage, and I’m doing my best to get it running again. The good news is that there are no startup issues. I had to make a few fairly basic switch adjustments to get to this point, but startup actually seems really good, and completes without any strange events (all the score reels reset, no chimes indicating a stuck pf switch, no buzzing relays, etc). And I can also confirm that the Ax relay gets fully released after startup, with all the Ax switches properly open.

The bad news is that, once play begins, either a 100 point or a 1,000 point target will cause both corresponding score relays to fire (relay M = 100 points, relay L = 1,000 points), almost as if they’re in series rather than in parallel. So if you hit a 100 point target, you score 1,000 points, every time. This seemed to be screaming “9-position issue on the 100 score reel is stuck closed”, but it doesn’t look like it will be that simple. The 9-position switch on the 100 reel is wide open (maybe ¼”) from 0 through 8. I even covered those switch contacts with paper, both at the reel itself, as well as at the 100 point relay, with no change… still 1,100 points are scored for every hit 100 point switch. Additionally, it even happens when the 10s roll over, which causes the 100 point relay to fire (as it should via the 10s 9-position switch), but then the 1,000 score relay fires even in that case too. So you don’t increase from 90 points to 100 points, you increase from 90 to 1,100 points.

This happens from the playfield during normal play, and it doesn’t have to involve a switch that might be make/break (i.e. one that awards 100 or 1,000 depending on the stage of play), such as those on the rollover sequence relays. Even the left/right pop bumpers, which are always 100 points and never 1,000 points, will result in a score of 1,100. Nonetheless, I did go through and inspect all the switches that the 100 and 1,000 point circuits might, as indicated in the schematics, share (make/break on the rollover relays and 0-position switches on the sequence unit), as well as pretty much every other switch and relay on the playfield and in the cabinet. Even the scoring wheel switches in the bottom cab look to be operating perfectly, although this bizarre scoring can certainly take place even in cases where the wheel doesn’t even need to turn (e.g. the pop bumper hit). It seems like I’ve done this switch inspection a hundred times, but it’s probably only been 3 or 4 times. I just can’t find any switch issues.

I can also replicate this bizarre scoring by moving around to the backbox and manually closing the 100-point relay. If I give the 100 point armature a good enough jab, then I can see both the 100 and the 1,000 point relays fire simultaneously. If I don’t give it a good jab, but just touch it very lightly, I’m only sometimes able to get the 100 point reel to move without the 1,000 relay also firing.
Again wondering if something on the playfield was involved, I tried disconnecting the jones plug that brings the 100 and 1,000 point signals from the playfield to the scoring relays. Once that is done, lo and behold… manually pulsing the 100 score relay does NOT cause the 1,000 point relay to fire, regardless of whether I hit it very lightly or with a good jab.

So this seems to suggest that the problem originates from the playfield, but for the life of me I can’t see from either the schematics or the playfield underside what the issue might be. There aren’t really that many things that can make the 1,000 score relay fire, and regardless every one of them seems to have an open switch in the circuit (according to the schematic, and confirmed by looking at the switches on the playfield). So I’m at a total loss. I’ve spent a lot of hours on it, and I’ve read a million threads. I’ve learned a ton doing that, but so far nothing to help me understand this strange scoring.

Any suggestions will be very welcome, this is driving me bananas!

Thanks for your suggestions, much appreciated. newmantjn, I will start on the cardboard work as soon as I get a chance. Briehl, I have cleaned most of them already, but will look for any I might have missed. This is a really strange one, and I hope I'm not already at the "grasping at straws" stage!

Hey thanks again for your time guys. Yes, the above is exactly what I had in mind too. The first is the zero-position switch on the sequence unit (the unit that tracks where you are in the sequence of knocking down targets, where position 0 is "hit the 2 jacks"). The lower two (1B and 4B) are the top outer rollovers, which will score 500 when unlit and 5,000 when lit. I have already checked all three of these, because it seems clear from the schematic that, for example, if the make/break is making on both contacts at once, you could end up with a "shared circuit" (I'm sure that's not the correct lingo, but hopefully you know what I mean). I even checked the 500 & 5,000 point relays (as suggested by Fred above) to ensure that they look good, and they do. But I plan to repeat the tests with paper over all of the appropriate contacts anyway as suggested earlier, to verify what my eyes are seeing... that visibly everything looks fine, all gaps are correct.

Again, thanks guys, it's just great to know I'm not in this alone. The fight continues, not going to give up now!