I have a motor speed control with the following transistors. I am having a heck of a time identifying them. I've had no luck finding a spec sheet on the web. Any help you may offer would be appreciated.

enter image description here

  • \$\begingroup\$ If, instead of photo of a mystery part, you could post a schematic of the controller, or the controllers's part number, or the manufacturer, or the motor it's controlling, maybe we could back into what it might be. So far though, I think that placeholder's pretty much on top of it since Teccor has never made transistors. Fine thyristors, but no transistors. \$\endgroup\$
    – EM Fields
    Commented May 7, 2016 at 20:41
  • \$\begingroup\$ Is the controller for a low voltage DC motor? Is it brushless? What is the motor current? \$\endgroup\$
    – Autistic
    Commented May 7, 2016 at 21:15

2 Answers 2


I don't have definitive answer, but I'll show my working up to this part so others may also use this approach to find these answers in the future.

Searching for the company logo I see this:

enter image description here

Which is possibly the right hand logo with the embossing obscuring it.

I got this logo picture from here.

If this is true, then this is not a transistor but either a Sensitive Triac or a SCR under that companies nomenclature.

However, I note that this is not a part number for Teccor. However, on a TO-220 package it is hard to put a whole part number. So this may be short hand version.

Searching on the data-sheets I cannot find the package labelling codes.

This company is now owned by littlefuse,so part labelling guidelines may have changed.

This should give you enough to test the part for characteristic behaviour. i.e. if you put this in a transistor tester and I am right, then it will fail.

  • \$\begingroup\$ unfortunately if you put a blown transistor in a transistor tester, it will also probably fail... \$\endgroup\$
    – user16324
    Commented May 7, 2016 at 22:00
  • 1
    \$\begingroup\$ @BrianDrummond yes, but the obvious point here is that if a transistor tester fails it may not be the that device has failed, it is that it may be in fact that the device is NOT a transistor. \$\endgroup\$ Commented May 7, 2016 at 22:02

Most of the time we are spending valuable resources to fix a faulty circuits. Finding and replacing defected components is the core of the process. Since the goal is always to get the circuit working, the chronicle of the old and bad components is not necessarily important.

What you should do is a through analysis on the circuit from which you pulled off the alien. The network of links around it will always give you good approximation about the type and specification of the device, even if the to220 lost its face..!!

As the other answer suggested, it could be a triac/scr. Its voltage rating should be at least 150% of supply voltage (RMS) and its current rating can easily determined by looking the final load.

The only remaining pieces of the puzzle is specification of the triggering current. Gate drive design of the circuit will give you ample ball park of this factor. Do research how the gate drive is designed for sensitive thrystor and compared it to the non sensitive thrystor.

While doing all these analysis you will actually gain lot and lots of knowledge which you may not get at all if you simply plug and play the defective component.


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