Biristor?

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Jaguarjoe

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Does anyone know what a "biristor" is? It has something to do with AC power control, maybe like a triac?

I have an old Milwaukee VS drill that died after only 45 years of use The trigger mechanism in the speed controller wore out. It's a relatively big controller with many discrete components. The phosphor bronze mechanical contacts wore out pretty much making it useless.

I bought a new "updated" replacement but it is very different from what I had. This unit is much smaller than the old one. It's made by Tyco and says "biristor" on its side. Of course I took it apart and it appears to be a small (TO-252?) three pin device attached to an equally small (.5" x .75") pcb with a few smd's on it.

When I put it in series with the drill's series wound brush motor, all I got was 0 or full speed from it. Having only two terminals on the package (line & load) it's pretty hard to miswire it.

The markings on the biristor are 1517042-1 and 4A052. Googling was no help.

If I could identify it, I could troubleshoot and see where my problem is.

Thanks,

Joe
 
The term you are referring to is known in the electronics world as a bistable resistor, a type of memory cell, however, what you are actually looking at there is an old Eaton speed control trigger mechanism that used the name Bi-Ristor. I didn't know that Tyco made such a thing. If I remember correctly, they originally contained 2 transistors, but what you are describing would seem to be different, quite possibly a Triac or Thyristor control circuit. Some close up hi-def photos might help troubleshoot it
 
Seems that eaton electronics used to make a variable speed switch called a bi-ristor.
If your runs full speed or off that implies that the triac is shorted, a common fail mode for a triac, maybe the device isnt rated high enough for your machine.
 
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