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SAC722 Motorola ?

Discussion in 'Electronic Design' started by Jamie, Jul 8, 2012.

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  1. Jamie

    Jamie Guest

    I think this is a SCR, due to the circuit it is in..
    Can any point me to a data sheet telling me what this is?

    This is small circuit that is part of a water pump system. There
    are only 3 heavy snap in contacts where #1 and #3 passes the AC
    current through 2 turns of wire around a Reed switch envelope.

    Another spade connection made from the start circuit that passes
    through a SAC722, which looks to be a SCR, of the Gate and cathode,
    through a 1k R and then through the reed switch, which then hits the
    gate of the other assumed scr. On the other SCR, the cathode passes
    through another coil that is wrapped around on just one end, not the
    middle, like the first one, and then goes back out to #2 terminal where
    it holds the circuit in the run position..

    It looks like if you short #2 lug, which will create much more
    current, the secondary coil will generate enough flux to work against
    the main coil so that the reed switch will open and thus unlatch
    this mess.

    If need be I can create a ASCII schematic of it, if any one is

    The strange thing about this is, I am having a hard time getting my
    head around this because the anodes of assumed (SCRs) are both joined
    together and go no where? That is like putting 2 diodes back to back.

    So, if any one has a data sheet site for the "SAC722" or, just confirm
    my suspicions of it being so, It would be much appreciated. Thanks.

  2. Phil Allison

    Phil Allison Guest

    "Jamie the Fuckwit Radio Ham"
    ** Motorola used to ( maybe ON still does) offer custom selected parts.

    In the case of their famous " MJ " series power transistors, the "M" was
    replaced with an "S" and the 4 digit number was a code known only to
    Motorola and the customer - ie, SJ1234.

    Motorola also made a series of triacs and SCRs that used the prefix " MAC"
    followed by a 3 digit number.


    This leads to "SAC" followed by a 3 digit code for custom selected versions.

    One can only make educated guesses at such a part's real identity.

    .... Phil
  3. Jamie

    Jamie Guest

    it turns out these units are TRIACS. 2 in series.. Not sure why there?
    Maybe to up the voltage handling or a redundancy ?

    Anyway, this board was designed to switch in the starting capacitor
    for a single phase 230 volt pump motor and uses a REED switch to monitor
    current. When current from the motor drops down, the REED switch opens
    and thus, no longer supplies a gate signal to the TRIACS. The motor's
    starting cap is connected to one side of these triacs while the other
    end of the string goes to the motor winding.

    There was a failure due to insufficient voltage while operating under
    emergency power. Apparently, the hot water heater was on and there
    wasn't enough to keep the well pump at full RPM's. TRIACS are not heat
    sink mounted. The motor is still ok.

    What this all comes down to is, I was asked by a dealer that sells
    and services these items and tells me this unit is no longer offered and
    a voltage sensing type kit is put in its place, however, the replacement
    apparently does not work as well. They would like to use a current
    sensing type instead.

    Thanks for the inside info on what Motorola does or did.. Kind of a
    sneaky trick..

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