I recently came across a great value on E-Bay, when a seller was offering 1000 pieces of 1% precision metal film resistors for $54.00 total.  I put the order in, and they promptly shipped from Hong Kong, arriving in Arizona within a week.  That was pretty impressive.

I have been a ham for almost 40 years, and a professional electronics technician for over 35 years.  Every once in a while, I see something new that is totally unexpected.  I’m not talking about new semiconductor devices or microprocessors, but something much more basic.

On examining the resistors for the first time, I thought… Man the lighting in hear is really bad.  I can’t make out the color codes on these things.

Later, I had a chance to examine them in sunlight, and the color codes still didn’t make sense.  For example, a 1 k-ohm resistor would normally have a color code of brown-black-red.  These 1 K-ohm resistors had a color code of brown-black-black-brown!

Huh?  What?  A few minutes of searching for “weird color codes” and finally “1% resistor color codes” yielded a chart that put everything in order ( from www.logwell.com ).

1% Resistor Color Code Chart (with 3 digits)

1% Resistor Color Code Chart (with 3 digits)

It turns out that some precision resistors have an extra digit in the value.  So instead of 1st digit, 2nd digit, multiplier… They have 1st digit, 2nd digit, 3rd digit, multiplier.  And to make it worse, you have to remember that the multiplier is for the three digits together.  So something in the 10K – 99K range has a red multiplier, instead of orange!

The chart above describes the odd color code effectively.  So be careful out there, when ordering new parts.  Things sometimes change from what you learned 40 years ago!

 

Here are a couple of 47 K-ohm (yellow-violet-black-red) resistors in place on a circuit board.

47K-ohm, 1-watt 1% resistors

47K-ohm, 1-watt 1% resistors