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old garage door opener circuit board

Discussion in 'Troubleshooting and Repair' started by James Okken, Jul 23, 2015.

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  1. James Okken

    James Okken

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    0
    Jul 23, 2015
    hi, another newbie here asking for free advice...

    i have an old garage door opener that isn't working. motor works but is not activated by the circuitry
    now im very novice but
    when i 'test' the circuit board's transformer with my multimeter I only get ~48v and ~4volts.

    the transformer, see attached picture, says
    pri 117 vac, 60Hz
    sec 38 38 vac 5.4VA

    i assume the transformer is bad, if im right I can't seem to find an exact match. would the one from this ebay ad possibly work, it seems "close"

    http://www.ebay.com/itm/TRIAD-Power...6-VAC-CT-06-12-amp-Prim-115v-PC-/161129093933

    thanks!!
     

    Attached Files:

  2. davenn

    davenn Moderator

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    Sep 5, 2009
    Hi James
    welcome to the forums

    OK how were you testing the transformer ... you haven't shown the pin connections for your one
    but going by the label, it has a single 38VAC secondary winding .... not sure where you were getting the second 38 from or the ~4V ???

    your transformer as stated on the label is a single 38V secondary at 5.4 Watts

    if you were measuring the secondary voltage with no load, then it would most likely have an open circuit voltage of between 45 and 50V ( that will drop to around the 38V under load


    Dave
     
  3. James Okken

    James Okken

    6
    0
    Jul 23, 2015
    oh sorry not -4volts I was meaning to say ~approximately 4 volts and ~approximately 48 volts, let me try to get more pics to show the pins. i was just getting readings putting the multimeter leads one on a pin one side of the transformer and one on the other.

    if the ebay one is close but has another secondary, I could just only use one secondary?

    there are 5 pins, 3 on one side and 2 on the other (the ebay one has 6 pins). thanks
     
  4. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    so you didn't stare how you were measuring the output

    where were you getting 4V and the 48V ?
    a pic of YOUR transformer and annotated where you were measuring what will hopefully clarify things :)
     
  5. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    ohhh and that eBay transformer wont supply enough current ... so no it's not a replacement
     
  6. Tha fios agaibh

    Tha fios agaibh

    2,168
    727
    Aug 11, 2014
    Agreed, Transformer sounds fine.
    If your lucky it's a fuse or relay contact.
    Full pictures of the pcb would be helpful. Does it do anything when you hit the button?
     
  7. James Okken

    James Okken

    6
    0
    Jul 23, 2015
    ok, thanks for the feedback. it seems you guys doubt it is the transformer. totally possible, im making assumptions here. i thought rather than me poking and hoping I'd post the pics youve asked for and ask you guys to please tell me where to test with my multimeter. (picture 5 has numbers on it). BTW: I can solder, relatively well...

    there are 3 pins on the outside, 2 pins on the inside, and two mounts at the middle. (i power this device via the pins on the black connector at the bottom of the first picture, i traced power and ground from the power source to the pins in this connector)

    1a.jpg

    2a.jpg

    3a.jpg
     
    Last edited by a moderator: Sep 2, 2015
  8. James Okken

    James Okken

    6
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    Jul 23, 2015
    3 more pics, thanks for your help!

    4a.jpg

    5a.jpg

    6a.jpg
     
    Last edited by a moderator: Sep 2, 2015
  9. Minder

    Minder

    3,104
    664
    Apr 24, 2015
    1-2-3 terminals appear to be from a CT secondary, you normally would expect an identical AC voltage reading from centre to each outside winding.
    (2 being the CT).
    I assume the voltage will be 19v 0 19v?
    6&7 AC power input.
    4&5 just mounting tabs.
    M.
     
    Martaine2005 likes this.
  10. Tha fios agaibh

    Tha fios agaibh

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    727
    Aug 11, 2014
    I'm suspicious of that transistor or regulator thing right next to the transformer.
    It can be seen in second picture with coffee cup.
    What voltage is across capacitor c1?
    Checking the diodes is good place to start. Unsolder and lift one lead out of board before testing.
     
  11. Alec_t

    Alec_t

    2,973
    804
    Jul 7, 2015
    In the second pic in post #8 it looks as though the big electrolytic cap has leaked, so would need replacing. I wonder, too, about the state of R3, which looks to have been cooking nicely.
     
    Martaine2005 and Tha fios agaibh like this.
  12. Martaine2005

    Martaine2005

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    May 12, 2015
    R3 definitely looks to have got hot. But that is it's job..
    Post 8 top left, looks to be a marking paint/spray. Not a leaking cap.
    Post 8 bottom left bottom has the same colour on the bracket.
    I could be wrong,

    Martin
     
  13. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    I'm with Alec that the cap leaked out.
    Only the bottom bracket bracket has paint.
    R3 probably got so hot it roasted c1?
    I suspect a shorted component across the power rail. Perhaps a diode?
     
    Martaine2005 likes this.
  14. Martaine2005

    Martaine2005

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    May 12, 2015
    Hey John. You are probably correct. That's why I love this forum.
    We all see see something different .

    Martin
     
    Tha fios agaibh likes this.
  15. James Okken

    James Okken

    6
    0
    Jul 23, 2015
    guys,
    thanks for all the suggestions, and i apologize for the long long long delay in my response, summer got in the way.

    Minder,
    testing shows 21v at 1 and 3. so your assumption was pretty much right.
    just to show what little i know I want to explain what I did:
    I tested:
    COM/black lead on 2 and V/red on 1 = 21v
    COM/black lead on 2 and V/red on 3 = 21v

    then I tested
    COM/black lead on GRN(supply) and V/red on 6 = 118v
    COM/black lead on 7 and V/red POS+(supply) = 118v

    ===
    Tha fios agaibh,
    could you explain once again please? I am unsure what you want me to "unsolder and lift one lead out of board" a diode or a capacitor?

    ===
    Alec_t
    the substance on that big electrolytic cap is a soft rubbery substance, similar to dry but flexible hot glue, is that what a leaking cap produces?

    thanks again guys, let me know what else you think!!
     
  16. Tha fios agaibh

    Tha fios agaibh

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    727
    Aug 11, 2014
    I'm just saying some components can't be tested while in the circuit board because connected components around it will give misleading results on your test meter. So instead of completely removing a diode, just remove one end to test it.
     
  17. davenn

    davenn Moderator

    13,866
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    Sep 5, 2009

    No, you and Alec are looking at a blob of glue holding the cap stable on the board ... a common practice
     
  18. davenn

    davenn Moderator

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    Sep 5, 2009
    see my last post, James :)

    Dave
     
  19. James Okken

    James Okken

    6
    0
    Jul 23, 2015
    so please educate me what it means on the transformer when it says primary 117vac and secondary 38vac. i had imagined it had one 110v input and two outputs of 38v and 117v.. but i'm sensing im way off... thanks
     
  20. davenn

    davenn Moderator

    13,866
    1,958
    Sep 5, 2009
    it means just that
    remember that your voltage from the mains isn't totally stable and does vary somewhat .... 115 - 120 would be the avg middle of that 117 so that is where they rate the transformer primary voltage
    the 110V would be close to a minimum and you could expect it to occasionally be as high as 125V
     
    Last edited: Sep 8, 2015
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