I need help identifying the green resistor, it is on a High Frequency board. This is a plasma cutter and the resistor cooked off due to dust and metal filings being sprayed into machine

it maybe a 0Ωresistor

Black Black white(?) brown(?)

MFR-12FTF52-0R can work for that resistance.

I’d be willing to bet it isn’t a zero ohm resistor. The cost of that resistor vs. a jumper wire would not make sense. It’s maybe a 5W resistor? I wonder if the value starts with 1 (brown) and perhaps the second color is burned off? Also, those bands that look black could be silver maybe.

I would unsolder that resistor and see if you can get a meter on it to measure its current resistance. Can you trace the circuit from the resistor to see what other components are connected to that resistor?

Hope this helps.

I tested it on the board and it read zero, then I touched it and it fell apart. It is wire coiled up inside but willing to bet it’s not a zero ohm resistor

Yes, that means it is a resistor with *some* low-ish value. If the coil of wire is still in one piece you may be able to measure the resistance from end to end to get an approximate value. If it still reads zero, it’s likely a small resistance like an ohm or two, or it could even be below one ohm, which is what I think it was.

Mike

I am more concerned with the voltage, as it is on a high frequency board and will need to handle that. Plus it is pretty big and the wire is thick, the main wire, not the coiled up wire which is finer than hair

Would you have an idea of what size it would have had?

Also what resistance would you want to try out?

As we have many that are super low ohmic values that are 0 to 2Ω.

Examples. Which also show the dimensions we list for these.

What kind of resistor would it be if it was this color combo from left to right black, brown, white, orange. What kind of voltage can it handle?

Here is a link to the 4 band calculator if you want to play around with different color combinations and see what you come up with and it should also give you options for what is available. Often this will tell you if it is a common resistance value or not.

-Robert

It won’t start with black, black is 0. As far as voltage, that has more to do with the physical size of the resistor. For instance, a 5W wire wound resistor with a physical dimension of 17.5 X 6.5mm has a working voltage of 500v while a .25W resistor with a physical dimension of 3.20 X 1.85mm has a working voltage of 200v.

It’s difficult without an accurate milliohm meter to get a reading from the resistive element (the wound wire) to be sure of the value which *could* have changed under the overload as could the color bands.

If you look at the colors from the bottom up as in the image, it could be GREY BLACK SILVER GOLD which would be 0.8 ohms 5%, but you will have to judge the colors yourself (if you can); a photo can be deceiving depending upon the monitor.

BROWN WHITE ORANGE would be 19,000 ohms or 19K ohms. How long was the wire after it was unwound from the resistor core?

Mike

I will check the wire length and physical dimensions but I am thinking this thing is 10kv or higher

Were you able to figure out the resistance value? And what are the dimensions of the part?

As a note, only a high ohmic value resistor could be rated for 10kV because of Ohm’s law.

For example, assuming it were a 5W resistor:

R = V

^{2}/W => R = (10kV)^{2}/5W = 20MΩ

So resistance would have to be at least 20MΩ for a 5W resistor to handle 10kV.

The wire is 7.5 feet long

Without knowing the actual value of the resistor and the colors are hard to read. It would be difficult to find an option to work.

So that’s a smallish resistance probably 1 to 2 ohms and from the physical size I’m guessing it’s between 5 and 7 watts. To be safe I would just use a 7W resistor, quite a few of those are 25mm long. If a 10 watt resistor will physically fit you can use a 10 watt resistor since it is only 5mm longer. That will give you many resistance choices.

We know it’s wire wound since you have the wire. The only two questions will be the resistance and whether it’s non-inductive or not. If it’s in an HF circuit it’s possible you will need a non-inductive resistor like this one: Resistor Aryton Perry winding and since it isn’t much more expensive I would just use a non-inductive resistor.

The only unknown is the resistance. Maybe a few others will offer suggestions for a 7.5 foot resistive element, but I think it will be 1 to 2 ohms and maybe it is a .8 ohm resistor like I said before. Start with a higher value and see what happen; you can always solder smaller value resistors in, but maybe do that in steps.

I hope all of this helps and you get the plasma cutter up and running again.

Mike

Before it fell apart, I put my meter on it and it registered 0 but it is not a milli ohm meter

I did put my meter on it before it fell apart and it measured 0

Right, then the meter does not have the resolution to measure small resistances. If you can find some resistors somewhere and measure them to see where your meter begins to measure low resistance, then you will have some idea where to start.

Hopefully you can find something that works.

Mike