(Topic ID: 220883)

DMD question noob here

By Risingjay1

5 years ago


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Topic Stats

  • 12 posts
  • 8 Pinsiders participating
  • Latest reply 5 years ago by Pin_Guy
  • Topic is favorited by 1 Pinsider

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    #1 5 years ago

    I just picked up my first pin, Getaway and was wondering if it's normal for the DMD to have a hum or buzz to it. The pitch of the sound changes when the screen changes.

    Thanks in advance.

    #2 5 years ago

    No.

    LTG : )

    #3 5 years ago

    Probably bad power supply filtering, look for capacitors with domed tops. Also, measure their ESR with a meter. Maybe you can borrow one.

    #4 5 years ago

    It will have a slight buzz to it under normal conditions. You can hear it in a quiet room when the game is in attract mode.

    #5 5 years ago

    Both of my WPC games have a very modest buzz or hum to them. Like Schudel5 said, you can only notice it when the room is quiet though.

    It’s especially noticeable in display test when the display is switching from all on to all off, or during attract animations that have a lot of the dots lit up. (I notice it on my shadow when the big “The Shadow” logo appears, for example) and it’s a brand new DMD, right out of the box.

    #6 5 years ago

    Great, thank you for the replies. I'll look through the caps and see what I can see. I'll be doing a recap and resolder on all the boards this winter. My room is dead quiet so you hear the dmd buzzing pretty good. I guess if it continues I'll just deal with it.

    #7 5 years ago
    Quoted from Risingjay1:

    I'll be doing a recap and resolder on all the boards this winter.

    Why?

    #8 5 years ago

    I hate to hear folks wholesale swapping caps when a game is performing fine. I really hate repairing what we’re nice boards before someone ripped all the through holes removing the OEM snapcaps.

    Not advised. This isn’t a CRT monitor.

    Chris Hibler - CARGPB #31
    http://ChrisHiblerPinball.com/contact/
    http://www.PinWiki.com - The new place for pinball repair info

    #9 5 years ago
    Quoted from ChrisHibler:

    I hate to hear folks wholesale swapping caps when a game is performing fine. I really hate repairing what we’re nice boards before someone ripped all the through holes removing the OEM snapcaps.
    Not advised. This isn’t a CRT monitor.

    Chris Hibler - CARGPB #31
    http://ChrisHiblerPinball.com/contact/
    http://www.PinWiki.com - The new place for pinball repair info

    I wouldn't be ripping through the boards. I'm an electrician by trade and have experience with electronics, mainly building my own tube amplifiers and repairing solid state amps. If you feel doing preventative maintenance on the boards isn't worth it then maybe I won't. I just know from experience that gear that is almost 30 years old typically need a refreshing. I by NO means am an expert with pins so I will take your advice. Thanks for the replies.

    #11 5 years ago
    Quoted from Risingjay1:

    I just know from experience that gear that is almost 30 years old typically need a refreshing. I by NO means am an expert with pins so I will take your advice. Thanks for the replies.

    We hear that often. Electrolytics do have a life expectancy. It's a matter of how critical that 100% peak performance from the cap is. On WPC-089 power/driver boards, the only caps that are really critical are C4 (100uf/25v) and C5 (15000uf/35V). Both of these caps are in the 5VDC power circuit and have been indicted for "reset" issues. I also routinely change C2 (100uf/25V) which is in the regulated 12V circuit. It sometimes leaks, takes out the traces, and 12VR is lost.

    Caps C6/C7 for example, are in the lamp matrix power circuit, both 15,000uf caps. They serve the same purpose as the 30,000uf cap systems of old used. No one =ever= changes/changed that cap. It wasn't necessary then and it's not necessary now.

    My apologies if you're experienced with PCB work and especially removing snap caps. I just see too many boards that become completely hacked by newbies. Pinball...where "if it ain't broken, don't fix it" is 100% valid.
    --
    Chris Hibler - CARGPB #31
    http://ChrisHiblerPinball.com/contact
    http://www.PinWiki.com - The Place to go for Pinball Repair Info

    #12 5 years ago

    When it comes to these WPC power caps, the old adage "if it aint broke, don't fix it." definitely applies.

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