1. Rest in Peace Paul (Kegger) If you would like to help the family in this time of great sorrow and need, you may donate on their GoFundme page: https://www.gofundme.com/mckechnie-medical-and-funeral-fund?
    Dismiss Notice

solder, diode, short, test question.

Discussion in 'DIY' started by stereory, May 19, 2017.

  1. stereory

    stereory Member

    Messages:
    57
    Electronic novice question:

    I soldered a silicon diode (+/-) onto a board. The two holes on the board were very close and I was a little heavy handed on the solder and I barely see any "green board" between the two joints. I want to assure I didn't short the two leads together.

    To test for that I would just check for continuity between the two leads? If there is continuity then I have a problem? Is that correct?
     
  2. RocketMonkey

    RocketMonkey Active Member

    Messages:
    255
    Location:
    Kansas city area
    How you can check that might depend on the circuit its installed in. But baring complications from any parallel components with meter on ohms red on the cathode(marked side of the diode) and black on the anode should be very high impedance, reverse the leads and it should be much lower. If you have a diode mode on your meter set it to that and check black to cathode red to anode, should show forward drop, typically about .7 volts depending on the type of diode.
     
  3. turnitdown

    turnitdown AK Subscriber Subscriber

    Messages:
    1,063
    Location:
    Tallahassee, FL
    A diode blocks any voltage if you test it backwards, so using a DMM in "OHM/RESISTOR" mode, touch the red lead on the anode end (no stripe) and the black lead on the other. (cathode) and if you have a short you will (likely) get a reading of 0 resistance. If your DMM has a diode tester, you can use that too.
     
  4. stereory

    stereory Member

    Messages:
    57
    I don't have diode mode on my meter. But if I check OHM between each side of the installed diode as you suggest, if I reverse the leads/polarity, wouldn't it just show the same impedance reading but displayed in negative?
     
  5. stereory

    stereory Member

    Messages:
    57
    Postive side of meter on stripped end of installed diode, common on opposite side is showing .5. The audible continuity alarm also sounds.

    So to confirm, that means I have a short right?

    Could other installed components cause this reading even if I did not have short?

    I ask that because I wonder if I should go forward and power the circuit and see.
     
  6. RocketMonkey

    RocketMonkey Active Member

    Messages:
    255
    Location:
    Kansas city area
    No, not negative. The measured DC resistance with a normal meter will be much higher, usually over load on a common meter, and much lower in the opposite direction. 20170519_214141.jpg

    5 million ohms that way.
    20170519_214200.jpg
    Over load, so higher than the meter can read this way.
     
    Last edited: May 19, 2017
  7. RocketMonkey

    RocketMonkey Active Member

    Messages:
    255
    Location:
    Kansas city area
    Other components can confuse things yes but .5 ohms either way is too low for a normal diode with a meter.
     
  8. elnaldo

    elnaldo Addicted Member

    Messages:
    6,333
    Location:
    Buenos Aires GMT-3
    If you doubt of your work, there is no doubt, do it again until you trust it.

    I'd remove the diode and measure resistance between both solder points without the diode.
     
  9. HypnoToad

    HypnoToad Ms Puss Puss Subscriber

    Messages:
    5,950
    Location:
    Melbourne, Australia
    Solder wick and plenty of flux to sop up the excess?
     

Share This Page