I previously posted about the rise in the occurrence of the Optima XM series main regulator resistor blowing. I’ve since had a few boards sent to me for repair, and a few users have also asked me about the resistor colour band codes. Below is my image of what an Optima XM & XM6 resistor SHOULD look like, before it burns up and scorches the board:

OptimaXM-and-XM6-resistor-undamaged

For those who want to know the resistance, the colour bands are the following: Gold, Black, Purple and Yellow, with a space between the gold and black bands. Here’s a diagram I made that shows how to interpret them:

resistor-color-code-allWhen working out the resistance of a pass-through resistor, you start by having the closest-together bands on the left. The resistor in the Optima is a 4 band one, so the resistance is worked out like so:

1. The first band is the Yellow one, which is 4;

2. The 2nd band is Purple, which is 7;

3. The 3rd is the Multiplier, which is Black at 1. The multiplier simply tells you how to multiply the first two values. Any multiplier with a K next to it is kilo (thousands, and the ones with M are Mega. So if our value of 47 was to be multiplied by 1k, a thousand, the value would now be 47,000. The Optima’s is simply a 1 multiplier, so it stays at 47, as you can’t divide it by 1.

4. We jump straight to the Tolerance band, which is Gold, at ±5%. The Tolerance band simply denotes how precise the manufacturing process of the resistor was, they can be 5%, 10% or 20%

Your total resistance is 4 + 7 * 1 = 47 Ohms ± 5%. Do not confuse it with a 47K resistor, it is 47 ohms, not 47,000 ohms, a K after the value indicates thousands.

Note that surface mount resistors and fuses do not have bands, they have the values stamped directly on them. If you are replacing a burnt resistor, clean the board around it with vinegar or contact cleaner to remove the burn marks. 99% of the time I’ve never had any actual board or trace damage, they are just burn marks from the resistor coating. You can use the methodology above for all the other resistors on the board, too, as they are mostly 4 band ones. If you are in any doubt I can do your repair for you, as I can repair traces and board damage professionally, use my contact form on the left sidebar to get in touch with me.

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One Response to “Optima XM & XM6 – Resistor Band Codes”
  1. Andrew Williams says:

    Hi!

    The contact form is not working for me…are you still able to help replace capacitors on XM6 PCBs?

    Thanks
    Andrew

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