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Don’t Be Lazy- About Checking Resistors On Board

By on May 27, 2012

When checking any resistor the best is to check them off board. Why? because to avoid parallel circuit that could produce wrong reading in the meter. Here is a reply that I've got from an ERG member concerning the TV problem that he had solved. Before I got that email he told me he had checked every components in the primary side and could not find any bad components. After few days he told me he had solved the TV problem. Below is the email:

"This resistor link to the the base of the switching transistor and to the optocoupler at the primary side,this resistor checked ok when check in circuit but open when check out of circuit, dont be lazy to unsoldered one of it leg to do checking. Thanks."

He mention that one should not be lazy in checking resistors off board (with one leg out from the circuit board). If you want a higher success rate you need to check not only resistors off board, you also need to check zener diodes, diodes, transistors and non polar cap off board. If you have the ESR meter, you can check the electrolytic capacitors on board.






  1. Roberto S.

    May 28, 2012 at 7:37 am

    Oh yes, I agree with your words!
    Otherwise you can check the electrolytic capacitors on board if you use the ESR meter.

  2. Antonio D.

    May 29, 2012 at 5:49 am

    yes I agree that the best way to find the resistor's value is to take off one leg and measure but it never happened in my experienced that the resistor is ok on board but high resistance off board. Think of a single resistor in a complex circuit (series-parallel ckt) w/o disconnecting one leg, you will not have any resistance higher than it's value and if that happened it should be open. In my point , any good resistor on board will always read in it's value or lower and will not be read higher.

    • Jestine Yong

      May 30, 2012 at 8:30 am

      Hi Antonio,

      In fact you are right it is either open circuit or read lower value. That resistor could have intermittent problem which is very rare but it did happenned.



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