Does the score motor run for 500 points? Could be that the score motor also scores 1000 points due to a faulty switch when the score motor runs, check the schematic to see what can score 1000 with a score motor switch in the path.

All joker targets and roll overs are 500 points
Drop target is 1000 plus 1000 for each lit joker....4000 maximum.
Hole is 1000 plus 1000 for each lit joker
Side roll overs are 500 and 3000 when lit.

Does this occur with both player 1 and player 2?
It's an important fact.
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Chris Hibler - CARGPB #31
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It could be a 9th position switch gapped too close on the 100's reel, but since it occurs when scoring 500 points (which causes the score motor to run), I'd suspect the reset path is still active to the 1000's reel. That would be either Player Unit switch P3C or P4C, depending if player 1 or player 2 is acting up.

Hint???

Jokers light corresponding rollovers and hole for additional score.
Drop targets score hole value.
IMG_2287_(resized).JPG

Scoring any 10X multiple of 5 always requires the score motor to run. A switch on level A will pulse 5 times to score 10, 100, or 1000 with each pulse. Usually, the switch is on motor 1A.

I still want to know if this occurs with both players. If not, I'd suspect the 9th position switch as noted above.
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Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://webpages.charter.net/chibler/Pinball/index.htm
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Here is my educated guess:

There is a joined Make/Break switch on either Trip Bank 1B, 2B, 3B, or on the Target Bank Sequence Switch (drop target bank). These are located at 4/5-E/F on the schematic.

Any of these M/B switches being joined (in other words both the make and break contacts made at the same time), can cause both Relays C (500 point) and D (3000 point) to energize together. To confirm, see if they are both energizing at the same time.

With both C and D energized, score motor is running, Score Motor 1A is producing 5 pulses per cycle to the M relay (your 500 points) and 1A is also producing 3 pulses to the L relay (your 3000 points). However, without racking my brain this late in the day, I am sure there is a feed back path through either Score motor 4C or 1B which normally hide the 4th and 5th pulse of the 5 pulses of 1A from getting to the 1000 point relay. This would explain 4 pulses getting through.

It's also inconsistently 4,500 point. Sometimes it scores 3,500 points. (I'm working on it with him)