Motor Control Circuit for vintage Universal Motor 3

[zaphod1]

I have an old hand tool that utilizes a universal motor that has failed, and there is a three-terminal device on the board in the tool that I have never seen before. It is where the problem likely lies (there is smoke residue around the device) There are no markings, orientation dots or any other identification on the component. I have attached some pictures and I have sketched up a quick diagram of the circuit with the unidentified device shown as a transistor. Can anyone identify the device shown in the attachments?
thank you in advance

 

[iop995]

Schematic it's not correct, check again; I think device is a triac.

 

[Comcokid]

Find an old SCR or Triac design guide. I think what you are looking at is called a "diac" and was placed in series with the control pin.

 

[zaphod1]

Yeah, I just used a transistor as a place-holder. I have never seen this form-factor before. Ia this a common older style for Diac/Triac/Thyristors?

 

[VEBill]

That package is itself "vintage"; it was becoming uncommon by the late-1960s.

 

[LiteYear]

For what it's worth, I think the attached circuit is the intended design. I've kept the same component designators, but I believe D1 might be a DIAC. The circuit then sort of resembles typical TRIAC/DIAC dimmer circuit designs. There might still be some errors though - in simulation, C1 charges far too quickly for the TRIAC to provide any chopping function.

 

[LiteYear]

Oops, had the triac around the wrong way. The gate has to be referenced to the terminal across the capacitor. Now it works!