Dumb Vactrol Q: NSL-32

[warriorpoet]

casing is generic and square- no cutout. There is a dot on one of the leads; is this the LED anode?

[madbean]

Here is an easy way to find out: put another LED is series (with its cathode to ground) and use a 4k7 resistor or similar. Apply 9v. If the second LED lights up, the mark on your vac is the anode (my NSL have the mark on the cathode, BTW).

[warriorpoet]

Here is an easy way to find out: put another LED is series (with its cathode to ground) and use a 4k7 resistor or similar. Apply 9v. If the second LED lights up, the mark on your vac is the anode (my NSL have the mark on the cathode, BTW).

I did the obvious thing: used my DAC55

It's cathode.

Cool tip! Thanks!