need part for honeywell st9103a

Discussion in 'General Electronics Chat' started by paulmars, May 13, 2010.

  1. paulmars

    Thread Starter Member

    May 13, 2010
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    st903a 1036(electronic fan timer), 4 lead IC marked:
    L 9948
    814
    (large dot) Y

    So far no parts suppliers can identify it. Honeywell wants me to just buy a new board for 150$

    Any ideas who makes this?
     
  2. Jazz Bass Special

    New Member

    Apr 9, 2010
    24
    5
    That "L9948" number is most likely an internal manufacturers part number.
    Trace out the circuit around the unknown IC.
    Post it here if you like.
    My bet is on it being a 555 timer IC.
     
  3. paulmars

    Thread Starter Member

    May 13, 2010
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    one lead gets 15vac straight from the circuit breaker. One lead goes to a resister, another to a diode, the fourth goes to a second IC with the same markings on it. One of its leads goes to a cap, another goes to a electrolytic cap and the fourth I forget where it goes.
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    A clear close photo would make this much easier.

    It may be a lost cause. Honeywell sometimes uses house numbers or ICs that are special made (or special numbered) for their purpose.

    A photo will help.

    There are 50463406 ways to imagine your spoken word wiring diagram. Can you take a picture and attach it here?
     
  5. paulmars

    Thread Starter Member

    May 13, 2010
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    [​IMG][​IMG]

    as you can see, there are two of these ICs. Both marked the same.
     
  6. paulmars

    Thread Starter Member

    May 13, 2010
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  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    I think they are opto's
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    From the cut-out underneath, that leads me to believe they are also opto-isolators.
     
  9. paulmars

    Thread Starter Member

    May 13, 2010
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    last night i tried to log on 4 times, it said each time pswd was wrong. Well, not it just accpeted it.
     
  10. paulmars

    Thread Starter Member

    May 13, 2010
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    last night i tried to log on 4 times, it said each time pswd was wrong. Well, now it just accepted it. Oh well.

    So, do you think that this IC is a weak link that could have been destroyed during a lightning hit? 3 different circuits in my house were damaged, including the ac/heat control st9103a. I tested the 3 relays on this board and several of the resisters and diodes. One of the leads on one of those ICs is directly connected to the 115vac in, so its live 24/7. Can I replace it?
     
  11. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    what are you up to?
    Do you have any idea what you are trying to do?
    Do you have any experience in handling mains operated or live circuits?

    Tell us what you know about live circuits and what you have to trouble shoot. I will not be engaged in anyone who have no experience in handling live circuits.
    This is for safety reasons, for your safety
     
  12. paulmars

    Thread Starter Member

    May 13, 2010
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    Your not my mother. You are not responsible for my safety. That being said, since I've already removed, tested and replaced several components on this board...I do know what I am doing. Im only here because I cant identify that IC and neither can several electronic supply houses.

    I do not believe in the throw away society and would rather fix then replace this board. The other day my neighbor threw away a NEC flat screen monitor. A little research on the net and a few 470ufd caps and its good as new.

    My house was built in 1954. i've added several circuits to it (new fuses, new wire, climbing in the attic, pushing wires down the walls. I've added a ground wire to some of the existing two wire outlets. I had the central AC/Heat unit installed(2001). I know when something is beyond my abilities, then and only then I pay the pros.

    If need be I will replace the board, but if I can fix it, I save money and the land fill.
     
  13. paulmars

    Thread Starter Member

    May 13, 2010
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    I've also tried to get the part and or a schematic from hoenywell and they are no help.
     
  14. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Safety issues are of primary concern, but since u know what you are doing then let's get cranking...
    What I do if I couldn't get a schema is study the circuit.
    I can help if you show me or give me an idea of what you have.
     
  15. paulmars

    Thread Starter Member

    May 13, 2010
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    specifically what do you need to know?
     
  16. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    well for a start I like to see the complete circuit board
     
  17. paulmars

    Thread Starter Member

    May 13, 2010
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  18. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    If you want to repair the board then you have to do some trouble shooting.
    If you not sure where to look at then show me the pics of your board, closeups.
    This way I can guide you
    By looking at the board I can tell which is which
     
  19. paulmars

    Thread Starter Member

    May 13, 2010
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  20. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    If it is the faulty one then show some closeups
     
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