Electronic – Decoding a resistor with weird colors

resistors

I have humidifier power supply with a blown 2W resistor.

From what I can see the colors are red, gold, gold, orange and grey or the inverse. I cannot tell the direction because the two external bands are in the same place.

What is strange to me is to have two gold rings in the middle.

How do I decode this resistor? It looks similiar at the one in the picture but I have an orange ring instead of red. I understand the picture is bad but I don't have a better one.

enter image description here

Best Answer

So the key to reading resistors like that is to try one direction, and if it doesn't make sense, turn it around and try again. For small-valued resistors, gold and silver are used as multiplier bands, and usually a fourth band on a 20, 10, or 5% resistor is a temperature coefficient (ditto a fifth band on a 1% or 0.1% resistor).

So, going by Wikipedia's color code article, because I'm too lazy to get up and get the ARRL Handbook from the shelf:

  • gray = 8
  • red = 2
  • gold = x 0.1
  • gold = 5% tolerance
  • red = 50ppm / degree K temperature drift.

So it's 8.2 ohms, 5%, low drift.

2W and 8.2 ohms implies that it'll never have more than about 4V across it, or around 0.5A. The low drift may be because it's expected to get hot yet needs to be accurate, or it may be whatever was cheap when that lot of resistors was purchased.

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