how can i check series of a diodes

Discussion in 'General Electronics Chat' started by raj90012000, Mar 8, 2010.

  1. raj90012000

    Thread Starter New Member

    Mar 8, 2010
    i want to check a series of diodes mounted on a pcb how can i do it
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Use a meter. If it has a PN junction check function, use that. Shorted and open diodes will be easy to spot. Forward conduction drops should be very similar for the same type of diode.
  3. someonesdad

    Senior Member

    Jul 7, 2009
    See here for some basics. Note you can usually check the diodes in-circuit unless there are low impedance paths in parallel with them.
  4. raj90012000

    Thread Starter New Member

    Mar 8, 2010
    i m not asking abt to check a single diode i want to knw the technique for checking diodes connected in series
  5. SgtWookie


    Jul 17, 2007
    Pass a voltage-limited controlled current through the diodes wired in series, around 20mA.

    Each diode will drop a certain voltage across itself, depending upon the diodes used and the current.

    If the sum of the voltage drops is in the expected range, then it's likely that the diodes are all good.

    If the voltage is at the limit, one or more diodes are open.

    If the voltage is less than expected, one or more diodes are shorted.