Testing of common electronics components

Thread Starter


Joined Aug 27, 2014
Hi all,

New to the board. I have a question per the thread title.

I am attempting to fabricate a test light for use in testing automotive
distributor components, eg, coil, ICM, etc. It involves an LED w/
built in resistor. Exactly, the LED in question is RadioShack
#276-270, which is rated for 12V and 20mA.

The question is, how can this LED be tested before its fabricated
into the test light? It has a red-insulated wire (+) and a black-insulated
wire (-). Can I simply put it directly across the 12V automobile
battery w/ red wire to battery positive terminal and black wire
to ground? I've tried resistance testing and continuity testing w/
a multi-meter but these were ineffective most likely due to the presence
of the built-in resistor.

Thanks for your input.


Joined Jan 29, 2010
Looking at the datasheet for that LED, just connect the Red wire to Positive of the 12V battery and the Black wire to the Neg of the Battery.
[B]RadioShack® 12V/20mA 4mm Red LED with Holder[/B]

Cal Rico

Joined May 1, 2012
Hey, RE: tips and tricks.
When testing wire devices ( am thinking of the Peak DCA55 transistor tester) connect up the test leads RED-Green-Blu e (as this is RGB), and RGB is how computer monitors use...Not only can you quickly remember which is Base-Common-Emitter it is also easy to remenber the sequence (as in American-Euro or Japanese Pin-out.
You may also use it in Red-Green-Black testing