MC-66 diode D11 broken

Discussion in 'The Projects Forum' started by sgarrupino84, May 27, 2014.

  1. sgarrupino84

    Thread Starter New Member

    May 22, 2014
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    Hello I have the card MC-66 with a diode D11 broken and I can not find the code and value. how can I? does anyone know the value / code?

    thanks :(

    MC-66 controller motor speed

    D11 what value is it?? please!!! :'(
     
    Last edited by a moderator: Jun 3, 2014
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    On the MC-60 the D11 is a LED?
    Not sure what the differences are for the 66?
    Max.
     
  3. sgarrupino84

    Thread Starter New Member

    May 22, 2014
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    D11 is Diode Zener but I do not know what value/code is it?

    thanks

    leo
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The MC-60 has a 1N742 for the 12vdc supply, most likely the same on the MC-66 as this is a typical way to produce the low voltage supply on these non-isolated drives.
    Max.
     
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  5. sgarrupino84

    Thread Starter New Member

    May 22, 2014
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    thanks, but d11 is diode zener code ?... :( see photo
     
  6. MaxHeadRoom

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    That should be 1n4742 for 12v zener, the reverse-engineered schematic showed 1n742 which is 150v.
    Max.
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    It's unusual for a zener to have absolutely no markings or stripes.

    Visually it looks to me like a DIAC, although I don't want to argue with Max as this is his area of expertise and he has schematics! ;)

    I am curious how the O.P. diagnosed the diode as "broken".

    If it is a DIAC it will measure as bad on a typical multimeter diode test.
     
  8. MaxHeadRoom

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    Jul 18, 2013
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    I don't have the schematic for the MC-66, just the MC-60, but it appears close, but the silk screen symbol on the board indicates a diode of some kind, I do have a stock however of the 1n4742 and they have the typical black stripe at the cathode end?.
    Max.
     
  9. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    How do you know the diode is broken? looking at the middle photo it says SCR trig, and an opto Moc3052 which makes me think its driving mains voltage to a Triac/SCR like this so i think it may be a diac or suppression diode.
     
  10. MaxHeadRoom

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  11. THE_RB

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    I have drawers full of of 400mW glass zeners of hundreds of sizes/types, and every one has at least one paint stripe (or text markings and an anode stripe).

    My guess is still a DIAC, which will test as open-circuit on a multimeter diode test but will conduct either direction once voltage is > 32v or so if the O.P. wants to test it further.
     
  12. MaxHeadRoom

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    I think you meant Cathode? ;)
    Max.
     
  13. THE_RB

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    Doh! :eek:

    Yes, a stripe on the "stripey" end.

    See how confusing it gets when a diode don't have no stripes? ;)
     
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