Resistor Code ?

[AeroEngy]

Due to a power surge a resistor on the Motor Control board of my treadmill cooked. It is likely that other components are also toast. However, since resistors are cheap and new control boards are not I thought I would try to replace the blown resistor first.

However, it has been a long time since my EE classes in undergrad and this resistor's color code doesn't make any sense to me. It seems to be an impossible combination since it either begins or ends with black ... which I thought you couldn't do ... also there are 2 gold bands in the middle ... which doesn't seem correct. To me it looks like Red, Black, Gold, Gold, Black (or the reverse).

Any help would be appreciated.

 

[Lorthreth]

Since the red is farther (seems atleast) from the black than the orange is from the leftmost black. Unless there's silver/gray next to the red, hard to see... (edit: just glare from the flash more likely)
So it would be 033*10^0±2%. And by size, 1W?

 

[Sheep221]

The color strips on resistors are still used? I haven't seen that for quite long time, any newer electronics, and parts just come with imprinted absolute value of their resistance.
Just connect multimeter and measure the resistance, it's not worth bothering to figure out the colors.

 

[PottedMeat]

The color strips on resistors are still used? I haven't seen that for quite long time, any newer electronics, and parts just come with imprinted absolute value of their resistance.
Just connect multimeter and measure the resistance, it's not worth bothering to figure out the colors.

I haven't seen many values printed on resistors except on SMDs and japanese power resistors. OP can try desoldering and measuring the value but if it took the surge the reading will be unreliable.

there's no identical good resistor on the board? - you could remove and measure that

is it a common board, maybe there's a schematic available

try playing with digikey's 4/5/6 band resistor code calculator
http://www.digikey.com/us/en/mkt/4-band-resistors.html

 

[Golgatha]

Due to a power surge a resistor on the Motor Control board of my treadmill cooked. It is likely that other components are also toast. However, since resistors are cheap and new control boards are not I thought I would try to replace the blown resistor first.

However, it has been a long time since my EE classes in undergrad and this resistor's color code doesn't make any sense to me. It seems to be an impossible combination since it either begins or ends with black ... which I thought you couldn't do ... also there are 2 gold bands in the middle ... which doesn't seem correct. To me it looks like Red, Black, Gold, Gold, Black (or the reverse).

Any help would be appreciated.

Is that an axial capacitor?

10 picofarad, 20% tolerance, 250V?

 

[Sheep221]

its resistor not a capacitor

 

[A5]

Due to a power surge a resistor on the Motor Control board of my treadmill cooked. It is likely that other components are also toast. However, since resistors are cheap and new control boards are not I thought I would try to replace the blown resistor first.

However, it has been a long time since my EE classes in undergrad and this resistor's color code doesn't make any sense to me. It seems to be an impossible combination since it either begins or ends with black ... which I thought you couldn't do ... also there are 2 gold bands in the middle ... which doesn't seem correct. To me it looks like Red, Black, Gold, Gold, Black (or the reverse).

Any help would be appreciated.

This site ( http://www.ankaudiokits.com/resistorcodes.html ) has a calculator for 5-band color codes. It comes out as 44 ohm, +/-3%. I'd verify that value with a multimeter, though.

The power rating is going to be a crapshoot, but it looks pretty big so I'd get one that is fairly beefy (1+ W).

 

[SecurityTheatre]

This site ( http://www.ankaudiokits.com/resistorcodes.html ) has a calculator for 5-band color codes. It comes out as 44 ohm, +/-3%. I'd verify that value with a multimeter, though.

The power rating is going to be a crapshoot, but it looks pretty big so I'd get one that is fairly beefy (1+ W).

Pretty sure it's actually 33ohm. Those seem more like orange than yellow to me.

 

[ScottMac]

The resistor color code: "Bad Boys Rape Our Young Girls, But Violet Gives Willingly for Silver and Gold"
Black(0), brown(1), red(2), orange(3), yellow(4), green(5), blue(6), violet(7), grey(8), white(9).

The third band is the multiplier. add that many zeros to the values of the first two bands.
i.e., brown, black, red, silver = 1,0,00 = 1000 Ohms, @ 10% tolerance (900-1100 ohms)

Silver = 10%
Gold = 5%
Colors = "precision" - i.e., Red = 2%

 

[AeroEngy]

I found a replacement board on e-bay that had some good high res pictures of the resistor in question but unexploded.

The pic (R46 in the middle) shows red, black, gold, gold, purple. I guess the heat could have changed my purple band to black (or see Edit below).

However, the digikey site won't take that combination as an input either using their 5 band calculator. It won't let me pick gold for the 3rd band. But if I use the 4 band calculator it comes out as 2 Ohms. Then with the 5th purple band would be a 0.1% tolerance. Does that sound about right to you guys? Thanks for all your help so far!

EDIT:
Just found this info from here:

...Generally, If an additional fifth band is black, the resistor is wirewound resistor. If an additional fifth band is white, the resistor is fusible resistor. ...

So either way it looks like a 2 Ohm and my black last stripe could just indicate that it is wirewound.

 

[A5]

The resistor color code: "Bad Boys Rape Our Young Girls, But Violet Gives Willingly for Silver and Gold"
Black, brown red, orange, yellow, green, blue, violet, grey, white.

Silver = 10%
Gold = 5%
Colors = "precision" - i.e., Red = 2%

Problem is this resistor has Gold in some of the value fields, not the precision.

OP, the other board you posted appears to have some minor differences from yours, at least as far as component source (the capacitors are different colors, and the tolerance value on the resistor at the front of the frame is different).

It's possible that that board uses a different resistor for R46 as well. The one on your board is Black, Gold, Gold, Black, Orange while the other is clearly Purple, Gold, Gold, Black, Red - I don't think the different dyes in the color bands would separate out before the whole thing just burned up.

 

[sm625]

Wow that is truly screwed up. You're not supposed to have gold on rings 2 of 5 or 3 of 5. That's just gibberish. And the photo clearly shows that it is indeed gold and not orange or yellow. Shrug.

You should remove R46 from your board, then ohm across R46 on your pcb (ohm across the holes). If that resistance is high, then that means the person who owns that known good board can ohm across his R46 and that reading will be accurate enough to let you know what the resistor actually is.

 

[ScottMac]

Gold in the third position is a 10-to-the-minus-one (-10^1) multiplier.
In the fourth position is the 5% tolerance

The violet band at the last position is the thermal coefficient ("M" - 5ppm/K)

Check this out ... http://en.wikipedia.org/wiki/Electronic_color_code

 

[sm625]

Why would a 5% resistor have a 5ppm temperature coefficient? And how are you supposed to know that this resistor only has two significant digits (2.0 ohms) when most resistors with 5 color bands have 3 significant digits (2.00 ohms)? I have dozens of different kinds of 5 band resistors right in front of me and they all have 3 bands for 3 significant digits, followed by a multiplier band and then a tolerance.

 

[ScottMac]

Why would a 5% resistor have a 5ppm temperature coefficient? And how are you supposed to know that this resistor only has two significant digits (2.0 ohms) when most resistors with 5 color bands have 3 significant digits (2.00 ohms)? I have dozens of different kinds of 5 band resistors right in front of me and they all have 3 bands for 3 significant digits, followed by a multiplier band and then a tolerance.

How would you express a single digit value? There is no "decimal point" color. To express two ohms, they give you 20 in the first two stripes, then a negative multiplier to reduce it to 2.
I guess it's not so much a "negative multiplier" but the "number of zeros to add" ... in this case it would be "subtract one zero."

The 5ppm is in Kelvin and apparently in addition to the precision. For a resistor of that value, it is likely to see some heat, and that may be a significant change. Plain carbon resistor change value as they heat up, the ceramics are more stable, all types have different characteristics.

Resistors in that value range tend to be high-wattage as part of a current limiter or power power divider.

 

[sm625]

How would you express a single digit value? There is no "decimal point" color. To express two ohms, they give you 20 in the first two stripes, then a negative multiplier to reduce it to 2.

A two ohm resistor should be red black black red (200 x 10^-2) and then the final band is the tolerance. Violet is 0.1%

 

[imagoon]

My book says this:

RESISTORS LESS THAN 10 OHMS
When the third band is gold, it indicates the value of the "colors" must be divided by 10.
Gold = "divide by 10" to get values 1.0 to 8.2

I found this site:

http://www.mikroe.com/old/books/keu/01.htm

And the show a 2.2ohm as Red Red Gold gold.

Red Black Gold Gold would give you 2 ohms then.

--edit--

mentioned here also:

http://www.1728.org/resisclr.htm

Third Gold = .1

 

[ScottMac]

Quote:
Originally Posted by ScottMac View Post
How would you express a single digit value? There is no "decimal point" color. To express two ohms, they give you 20 in the first two stripes, then a negative multiplier to reduce it to 2.
---------------------------------------------------------------------------------------

A two ohm resistor should be red black black red (200 x 10^-2) and then the final band is the tolerance. Violet is 0.1%
__________________

That would be a 200 Ohm resister with a 2% tolerance. IF there is a violet band after all that, then it is a 5ppm/K temp coefficient.


See Imagoon's links above.

 

[Cogman]

Are you absolutely sure the resistor is burnt out and not something else? Resistors are pretty hardy fellas, even to pretty extreme power surges.

 

[imagoon]

Are you absolutely sure the resistor is burnt out and not something else? Resistors are pretty hardy fellas, even to pretty extreme power surges.

Considering it shattered the dip and you can see the internal coil, I would consider it burnt out.

 

[mindless1]

^^ That would be my guess too, that the resistor has merely lost some of the coating but is electrically ok, that maybe a switching transistor is fried but an equivalent replacement shouldn't be expensive.

Anyway, check continuity on the resistor legs. It's weird that you didn't mention any tests like whether you measured a resistance across it.

Considering it shattered the dip and you can see the internal coil, I would consider it burnt out.

Physically damaged and ought to be replaced yes, but in the short term it may be electrically functional, not necessarily the reason the board doesn't work.

 

[imagoon]

Physically damaged and ought to be replaced yes, but in the short term it may be electrically functional, not necessarily the reason the board doesn't work.

True but for a resistor (or any component really) to blow apart its package, something had to heat up and be converted to gas to breach the package. Generally that changes the devices characteristics. However yes I agree that the board itself may (likely) have other parts that are bad. I mean a resistor is a 2 leg device... something else on the board also had to sink that power. You hope it was a varistor that is also easy to replace and is supposed to be the device that dies to protect the board but you never know.

 

[mindless1]

^ Less true for wirewound resistors than many other components. IF the wire is intact the package doesn't matter except for eventual degradation from heat -> oxidation.