[Elecraft] Installing the K3 AGC Mod (SMD)

[Ron D'Eau Claire]

Hello David:

The diode in question has about a 1.6 V forward drop. 

I've use that technique for a number of years with both Fluke and other DMMs
and it's always worked for me on red, yellow, green and "white" LEDs. 

As I mentioned, it only works in 'diode check' mode. Ohms scales on modern
DMMs typically don't have enough voltage to turn the diodes on, in my
experience. 

Your point is a good one though. It might not work for all DMMs out there.
But, if it does, it's a positive indicator. It's  been invaluable for me
once diode leads are cut since for many diodes only the lead length
indicates the polarity! 

Ron AC7AC 

-----Original Message-----

Ron D'Eau Claire wrote:
> If you have a DMM with a diode check feature, just probe the LED 
> terminals. When you have the positive lead on the anode the DMM will 
> indicate a forward biased diode junction and the LED will light up!

LEDs have higher forward voltages (much higher for blue ones) than 
ordinary diodes, so some meters may light the diode, but show full scale 
and some may not even light the diode.

My meter will light up to at least green, but shows an off scale drop 
for even red.

-- 
David Woolley