Help on identifying resistor value please.

Discussion in 'General Electronics Chat' started by bordonbert, Mar 31, 2016.

  1. bordonbert

    Thread Starter New Member

    Feb 21, 2012
    18
    0
    I feel totally stupid asking this after a long lifetime in electronics but it is something I've just never seen before. And it's plain bugging me!

    I have a 5W power resistor which is defying my rules of resistor banding. You can see 3 of these which are actually in parallel on the PCB. They are listed as 100R 5W on the schematic and they meter out as 33.3R exactly. But if those bands are Brown, Black, Brown, Gold, Black, isn't that usually denoting 10.1R, 101 x0.1 @ 1%? Yes 10.1R is a silly value for a power resistor but what the heck!

    And with Brown, Black, Brown, Gold metering out at 10 x10 @ 5%, more in line with a 5W resistor, then what is the Black band on the end for? I've never come across a black temp coefficient. If it is to be ignored how do you know it is to be ignored? Is it just the case that nowadays power resistors are being marked as 5 band but only have 4 relevant ones?

    I know this is going to turn out to be a simple "ignore the usual rules this is an odd case", but someone will have seen this before and can explain what the odd last band is doing there.

    Power_Res_Chain.jpg
     
  2. #12

    Expert

    Nov 30, 2010
    16,345
    6,829
  3. bordonbert

    Thread Starter New Member

    Feb 21, 2012
    18
    0
    Thanks for the link, I originally checked out my own thinking with a link that looks identical to that.

    http://www.hobby-hour.com/electronics/resistorcalculator.php

    However, as you can see it didn't have that entry for the black temp coeff. The power and accuracy of the internet!!!! Mind you the clue is in the word "hobby". That now makes sense and my world has stopped rocking! Many thanks for the succinct reply and the answer. :D
     
Loading...