In Reply to: Silicon Controlled Rectifiers posted by Mike Navarrette on 07/23/01 at 11:39 AM:
Testing the SCR for simply being an SCR would be to induce triggering on some low power source.
An example: There is a very low power SCR in a TO-5 case, part number 2N2223. I used to check those with a Simpson 260 VOM on the resistance range R x 1. I'd put the "+" meter lead of the ohmmeter to the anode lead of the SCR and the "-" lead of the ohmmeter to the cathode lead of the SCR. No current would flow. Then, I'd momentarily touch the SCR gate lead to the "+" meter lead too and then disconnect it. The SCR would latch and carry current from its anode to cathode where it hadn't done so before. Then, momentarily disconnecting and reconnecting the SCR anode wire would cause the SCR current to stop again.
This was a simple, but effective check of that SCR. You could rig up some similar arrangement for the devices you need to check.
John Dunn - President