(Topic ID: 298008)

Q: rottendog power driver gi is all dim

By pinballplusMN

85 days ago


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  • 31 posts
  • 10 Pinsiders participating
  • Latest reply 81 days ago by pinballplusMN
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    #11 83 days ago

    Drivers?
    LM1085's are actually low-dropout voltage regulators - 5V, 3A.

    ... confused.
    Are they actually using a 5V regulator to the lamps and turning the regulators on and off?
    Note that although they are rated up to 3 amps - in order to get three amps through them, they must be kept within liquid nitrogen.
    Novel idea, though.

    #13 83 days ago

    Picture is worth 1000 words.
    Curious - which TRIAC are they using?

    #15 83 days ago

    I wonder if the LM1085's used at the TRIAC locations were a manufacturing error that didn't get caught during their 'strenuous testing'.

    Regarding TRIACSs --
    MAC210A8G -- formerly made by On-Semiconductor (Motorola). On-Semi sold off TRIACs and SCR's to Littelfuse (yes, the fuse manufacturer) so they are now made by Littelfuse.

    Just a quick scan through the data sheets and compared the MAC210A8G to the often used BT138-600E:
    Both are rated for 600V which is more than adequate.
    MAC210A8G has a 10 amp rating, BT138 has a 12 amp rating.
    The MAC210 requires 3x to 5x the amount of gate current (IGT) to trigger the TRIAC.
    The MAC210 has a slightly higher VGT trigger voltage than the BT138.
    Since the gate is driven by a 2N5401 - I don't see VGT or IGT being the issue.
    Not a lot of difference but the BT138's were a tiny bit better than the MAC210s in nearly all other specs, I didn't see any real show stoppers other than the three small ones listed above.
    Note - I only glanced through the specs and didn't do any real digging into this.
    One thing that can make a big difference -- is the heatsink used by RD the same as those used on the original Wms boards?

    Probably the reason they used the MAC210s - they're widely available while the BT138-600E parts are a bit harder to find and cost more.
    The pinouts were the same and so is the biasing circuit - the BT138-600E parts can be a direct replacement.

    #25 82 days ago

    WOW! Clearly they were shipping untested boards.

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