(Topic ID: 238454)

U-Shape Optos registering in reverse?

By Pintopia

1 year ago

Topic Stats

  • 3 posts
  • 2 Pinsiders participating
  • Latest reply 1 year ago by Pintopia
  • No one calls this topic a favorite


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    #1 1 year ago

    I have a Sample (or early production EarthShaker) that I have restored with a new playfield cabinet decals etc... I was working great until the sinking building started having issues. It sometimes would not move or would move but with significant motor noise. It would always fully drop or fully exstend when it did work. I first changed the 3906 transitors did not fix it. Then I changed the motor that seemed to correct the problem however now I'm getting a switch error for opto2 which is the height switch and the building only raises half way. I changed the opto did not help. In testing the optos they only register in the switch test upon exit of the blocking portion of the opto interuptor. in other words when the interuptor first block the opto beam nothing when the interuptor exits the opto it the registers which causes the motor to stop and the building is only half way. This exists in both optos.

    Any ideas?


    #2 1 year ago

    I've looked at this, even though I don't have an Earthshaker. There is a schematic on IPDB, some parts list. Not much else, the sinking building optos don't show up in the switch matrix diagrams in the standard manual. One thing that is should be identified is whether the games program design expects a normally closed or normally open optical switch (in other words, does the opto turn on when it senses light or does it turn on when it expects to see dark).

    I wouldn't expect that the wrong opto is installed - unless the optos and the feature were working correctly and then after the rework was done it cropped up. Not much else I can come up with at this time, hopefully someone with a sample game can assist further.

    #3 1 year ago

    Thanks for taking a look at this. I think the issue maybe the motor. I replaced the motor due to it getting older and not working. I noticed that if th motor turns clockwise the building functions properly if reversed it does not as the interrupters are passing the optics at a differepoint. In bench testing bothe the old and new motor I noticed that it would randomly change directions when starting up at tdifferent times. I installed back in the game and it exhibits the same behavior. It’s a 24v ac motor and in reading to change direction of an ac motor the polarity must be switched. So I’m not sure how Williams is maintaining the polarity?

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