(Topic ID: 304675)

Bizarre system 11 power supply 5 volt problem

By Whiskers

7 days ago

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  • 13 posts
  • 7 Pinsiders participating
  • Latest reply 10 hours ago by snyper2099
  • Topic is favorited by 1 Pinsider


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    C7C8 (resized).jpg

    #1 7 days ago

    Trying to get my pins fully up and running before Thanksgiving (two sys 11s and a sys 9). One of my system 11 power supplies refuses to keep 5V consistently- sometimes it works for a couple of hours then stops; other times I fire it up and the 5V is missing entirely from the get go. I know its this board because the gripe follows the board when I swap it to the other sys 11 machine. C8, C12, and C10 are new within the past year- I've never heard or read of the IC or the transistor going bad, so I'm hesitant to troubleshoot by swapping those out. What am I missing? Could it be C15? The fact that sometimes it has 5V and eventually doesn't, and other times it doesnt have it at all makes me think it is most likely a capacitor and not the chip or transistor.

    #2 7 days ago

    When you fire it up and 5 volts is missing. Quick turn it off. Then turn back on. If 5 volts is back then, I'd suspect a capacitor issue.

    LTG : )

    #3 6 days ago

    Thanks for the note. I turned the pin on and did some basic 5V checks- I got something like 1.2 then .822 everywhere I'm supposed to have 5V. Then, as it sometimes happens, the 5V "came back" as I was doing the voltage checks and everything checks out fine now (at least until the next time the 5V dissapears again)- no idea why.

    What would it look like if the IC or transistor were bad? I'm scratching my head about what could be causing the 5V to come and go like this- I thought that if a capacitor was bad, it'd never work.

    #4 6 days ago

    Sounds a lot more like a cold solder joint(s) on the header pins or a component. Re-flow solder on all the header pins on your power supply board first.

    #5 6 days ago

    The ic does handle the 5v on system 11 power supplies, but it either works or it doesn't. If the 5v works after the game "warms up," then it's probably a capacitor issue.

    #6 6 days ago

    Measure DC voltage at pins 4 and 5 of the LM723.

    If the voltage differs then the regulator has failed.

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

    #7 6 days ago

    First thing I would do is check power going to the regulator.
    Are C7 and C8 originals? What voltage do you see at the cathode (banded end) of D1?

    C7C8 (resized).jpg
    #8 6 days ago

    G-P-E , Ed...reference the schematic you posted above.
    The Data East PS is identical (or I'll say nearly so as I haven't done an exhaustive comparison. At least the basics are the same).

    C2 on a DE PS is the circuit equivalent of C7 on a WMS PS (100uf).
    C2 on a DE PS leaks quite frequently.
    C7 on a WMS PS never leaks (well, I've never seen one leak).

    C7 on a DE PS is the circuit equivalent of C11 on a WMS PS (330uf).
    C7 on a DE PS leaks quite frequently.
    C11 on a WMS PS never leaks (well, I've never seen one leak).

    Can you offer a reason as to why this might be?
    Difference in component brands used by the OEMs?

    Enquiring minds want to know...
    Chris Hibler - CARGPB #31
    http://ChrisHiblerPinball.com/Contact ... for board repairs
    http://www.PinWiki.com - The Place to go for Pinball Repair Info

    #9 5 days ago
    Quoted from donjagra:

    If the 5v works after the game "warms up," then it's probably a capacitor issue.

    Yes. Usually, if a power supply (or whatever electronics) works only after warming up, it probably has a failing electrolytic capacitor. But if it works cold and fails after warming, then suspect a bad IC. Heating specific places with a hairdryer and cooling with cold spray help pinpointing the failing part.

    Bad capacitor can't usually be detected by a capacitance meter, or multimeters capacitance range. The microfarads may be there, but the capacitor internal resistance (ESR) gets higher with age, and that prevents capacitor working properly. When in doubt, replace.

    #11 4 days ago

    hi guys, appreciate the insights. As I suspected would happen, the pin with this PS worked perfectly all yesterday for our get together… and today when I turned the machine on, the 5V is gone again.

    I’ll do the tests as described above and write back when I’m done with the results.

    #12 1 day ago

    Post a picture of the board, sometimes this group is crazy genius on a visual inspection.

    #13 10 hours ago

    Your symptoms still sound related to a failed connection and not a failed component.

    Typically, faulty components are constant (yes, even capacitors) while faulty connections come and go with things like vibrations and heat.

    While it's always a good idea to replace old capacitors.... caps specifically do not typically "work for hours", then fail and then "work for hours" again. When they fail or begin to fail, they always show "build up" and "trickle down to failing" symptoms that are consistant. Your abrupt/sudden/random symptoms don't fit this very well. Do not overlook the obvious.

    Next time the game is working properly, carefully wiggle the connectors to see if you can get it to crash on purpose. If you do, address those connectors/pins where it failed. Intermittent problems are the most difficult to track down but you can do it if you are careful and patient!

    Hey there! Got a moment?

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