[HomeBrew] identifying component

[WB6BLV Central California]

those are power thyristors, either SCR or triac

previous post bout how to test is pretty accurate... you may need to allow
sufficient current throught gate (small term) and through main circuit
(smaller current limiting resistor values) in order to get them to 'fire'...
used many of these over the years for welding machines and large motor (50
hp and up) control...

John