Sealy supermig 250/10

  1. Pippasdog New Member

    Wirral uk
    Hi guys
    First Post so please go gentle with me.
    My friend has a sealy supermig250/10 and unfortunately the main switch has gone. It has on it bremus series 12. I have contacted sealy but as helpful as they are as its quiet old they don't have a manual they have suggested a switch but carnt guarantee its correct.
    Does anybody know were a can purchase the correct switch and have a manual with a wiring diagram please as my friend has made the silly mistake of not taking photographs before removing it. Long shot I know thanks in advance
  2. a111r Member

    You won't buy one with the necessary information.
    The old Sealey / Telwin (185 amps upwards) tend to have the same Italian made 6 position rotary voltage selector switch.
    I have one undergoing repair, so I could send you photos, fwtw...
    The wiring from the transformer secondary always has a 'set' as to it's position. Plus a DVM can be used to compare tap off resistance and hence position.
  3. eddie49 Member

    Hello, and welcome to the Forum !
    Rather than "Bremus", I think you will find the switch manufacturer is Bremas. As a111r has said, these rotary cam switches are unique, configured-to-order, and you will need to quote the full number off the switch. These guys:
    seem to know something about them, and may be able to supply an equivalent.

    However, from the circuit diagram: Sealey.png
    it looks like your friend got lucky - it is just a simple 1-pole 6-way switch. There are 5 transformer tappings, and position 0 is "Off". Any 1-pole 6-way switch that can handle the primary current will do the job.
    To identify the wiring, unless the solid wires have been pulled around a lot, you should still be able to see which is the first and the last wire, where they exit the transformer plastic bobbin. There will then be a large gap to where the far end of the primary winding exits, and goes to the neutral via the contactor ( heavy-duty relay ). The lowest-power tapping ( position 1 ) will have the highest resistance to the far end, and the primary winding resistance will progressively decrease going up the power ranges. However, the whole primary resistance will be low - a couple of Ohms - with small changes in resistance for each step.

    As you step up the power ranges, the DC voltage at the MIG torch tip will increase steadily, from about 15v to 32v, so this would give you an alternative way of identifying the sequence of the 5 power tappings.

    Full manual here:
    Last edited: Aug 12, 2020
    a111r and wacky7791 like this.
  4. Pippasdog New Member

    Wirral uk
    hi guys
    thanks very much for your replies i really appreciate your help . looking at the drawing eddie49 very kindly posted you would ( forgive my ignorance at least i would) expect there to be only 7 cables going to the switch ( 2x at terminal 3 ) however looking at the switch there is at least 9 ? / any electrical experts out there that may be able to shed some light on this .thanks again
  5. eddie49 Member

    Yes, I agree that from the diagram there should be 7 wires at the switch. One of them being AC mains in, five tappings to the transformer, and one extra wire that feeds the auxiliary power transformer from terminal three ( picking up a lower voltage from part-way down the transformer primary ).

    The existing switch may have more available terminals, but I guess they are not used. Position 0 is Off, so it will have a screw terminal, but nothing connected. These rotary cam switches are notoriously complicated. Some may need external links from wafer to wafer to achieve the required function. However, if the existing switch is broken and unobtainable, you need to source a suitable 1-pole 6-way switch. The new switch may come with a functional diagram, and should be fairly easy to figure out with an Ohmmeter.