# A mystery resistor...

#### RoverAllOver

Joined Jan 23, 2024
3
Hello folks, I'm trying to fix an ATX power supply, among other problems it has a blow resistor with markings that don't make sense to any of the calculators I've tried.
I'm reading it as red, red, silver, gold, green.
It is a large resistor (15.5mm) on the high voltage circuit.

Here is a huge picture - can anyone help me with the resistance and wattage values?
Thanks for any help.

#### MrChips

Joined Oct 2, 2009
30,820
Before replacing any blown component you need to determine what made it blow in the first place.

#### RoverAllOver

Joined Jan 23, 2024
3
Yes I'm working on that, I've found a blown fuse and the resistor so far.
There was a loose piece of uninsulated copper wire in the case which may be the root cause.
I'm going to check the large transistors and diodes as well, so far everything looks good.

#### Michal Podmanický

Joined May 11, 2019
35
I would say 0.22 ohm about 2W. It is obviously poor wattage rated.

#### sagor

Joined Mar 10, 2019
912
While it seems badly "cooked", it might still be close to the original value. Lift one leg and measure it....
If it is a really low value, most ohm meters will simply show a zero reading, or close to it.

#### WBahn

Joined Mar 31, 2012
30,066
Red - 2
Red - 2
Silver - x0.01
Gold - 5% tolerance
Green -- Something else.

The green might indicate a few things -- often either a reliability rating or a temperature coefficient. If it's a tempco, it would be 20 ppm/K. Not sure whether green is every used as a reliability band, but if it were, it would probably be a failure rate of 1 ppm/1000 hrs, I can't imagine a resistor being used in an ATX power supply having a reliability band (this is almost never used on commercial resistors, it is part of a military specification), so it's almost certainly a tempco.

So 0.22 Ω, ±5%, 20 ppm/K

Not a guarantee, but highly likely.