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Need Triac

Discussion in 'Electronic Repair' started by [email protected], Jun 16, 2004.

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  1. Guest

    I have a Black and Decker reciprocating saw. It's a variable speed
    type, and has a Triac. It quit working, and when I opened it, I found
    one of the terminals broken off the triac (right at the body, so I can
    not solder it). Otherwise the saw works fine.

    Two questions

    1. Can I wire the motor directly to the line (120VAC), thru the switch
    of course. I need to use the saw and dont care about variable speed
    for the moment, I need full speed?

    2. Does anyone know where I can buy a GE ST2 triac? B&D parts wants
    to sell me the whole switch assembly for more than what I am willing
    to pay for this old saw. I dont need the switch, all I need is the
    triac and a pop rivet to mount it. I know most places these days have
    a minimum order amount. I just need this one part.

    To reply by email,
    handyman AT centralpets DOT com
  2. Guest

    GO to:

    They call this item a Diac. It is used to trigger a Triac, not replace
    one!! If you bypass this device I would expect more damage to your saw.
  3. Bill Jeffrey

    Bill Jeffrey Guest

    I'll try again here.

    First, the link to American MicroSemi does indeed bring up ST2 as a
    diac. It seems to be a small two-lead glass diode package, which
    doesn't sound like what the OP is asking about, since he is talking
    about riveting it down.

    The ST2 data sheet on the same site
    calls the ST2 a general purpose silicon rectifier diode, 160 amps at 400
    volts. This doesn't sound like like what the OP is asking about, either.

    The Mouser catalog search on ST2 also leads to diacs, but the ST2 is
    again a small two-lead glass diode.

    A further Google search leads to
    where the ST2 is a triac, with three leads and a tab to rivet it down.

    My conclusion is that there is more than one part out there with the
    nomenclature ST2. Be careful what you order.

    Bill Jeffrey
  4. Probably. Unless they've done something strange, the motor will work
    fine straight from the mains.

    NOTE: If you're not *absolutely sure* about this, but want to try it
    anyway, run a 60W bulb in series. That way, if anything does go wrong,
    it won't blow up.
    Any suitable device will work; use the highest rating you can get
    (600V, 16A will do nicely) that will fit the space. TIC226F is a
    number that comes to mind.

    However, make sure it's not in fact a quadrac (a triac with a diac, as
    described by others, inside the package. If you use the wrong one, it
    won't work.



    ....Daddy, what does "Formatting Drive C" mean?
  5. Guest

    Thanks for all help....

    OOPS, Sorry, I read the schematic wrong. You are correct, the ST2 is
    a diac. They had it labelled right next to the triac, and the triac
    was not given a part number. However, after scraping off the silicone
    or whatever it is, from the triac, the part number on the triac is a
    G.E. SC146D.
    I contacted Black & Decker, and this part is not available, since they
    said the saw is obsolete. However, they said they could sell me a
    universal speed controlled switch, which would fit the saw, but would
    cost nearly as much as a new saw.

    This saw worked perfectly, it's just that one of the pins broke off
    the triac, right at the case, so there is no way to solder it. (I may
    have broken it when I opened the case to lubricate the gears, since
    the silicone was pulled loose too).

    Anyone have any specs / replacement part suggestions for this triac,
    and know where I can buy one without having to order $50 (or more)
    worth of stuff. I wonder if Radio Shack might have a replacement,
    then I can buy it directly and eliminate all the mail order hassles.

  6. Mark Zenier

    Mark Zenier Guest

    My old Teccor catalog says that they made this, at least within the
    last 10 years or so. Try Mouser or Digi-Key.

    It's a 400 volt 10 amp, non-isolated TO-220 Triac, 50 milliamp gate
    trigger current. Doesn't look like anything special.

    Mark Zenier Washington State resident
  7. Guest

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