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I'm attempting to repair a burned out resistor on a refrigerator control board. I can't seem to find a valid value given the color bands that I SEE . Any help would be appreciated.
The working resistor of the same size/type/markings measures 23 ohms.
If it is the same, it would probably a standard value of 22Ω, if there was no other resistance in parallel with it. The sure way is to disconnect them from the ckt then measure them.
That was the easy part. Now find out why the resistor died so it won't happen again.
Thanks for the reply. Well the cause is pretty easy to identify....me. I tried to run the fridge on a 1500w modified sine wave inverter. Ran fine while I was watching it the first 10 minutes. But a tell-tell melting smell greeted me upon return after 2 hrs. I didn't think a 10 yr old fridge would be controlled by a control board with "sensitive electronic components" but I was wrong.
That's what's throwing me off....the blue tolerance band. .25% tolerance doesn't seem appropriate. Also, I can find plenty of 22 ohm resistors, but how to find the wattage? Based on the size (15 mm length, 4-5 mm diameter) I think it is 1/2 watt...but I don't know how to test.
Very difficult to tell from the photo, but is it red-red-green(???)-silver-blue(???)
Back in the old days, resistor manufactures would make "fusible resistors", which had (if I remeber correctly) an additional band.
These resistors had the characteristic to be 1 watt and above, and when they failed, they would open without any sign of overheating in the body.
I was introduced to them the hard way via a Zenith TV set in the early 1980s....could not figure the colors out, so had to purchase a service manual from Zenith.
In the manual it was listed as a critical component, I suppose to both limit inrush current and act as a fuse...... Your circuit could be similar.
Thanks for the reply. The circuit board is pretty simply and these resistors are fairly isolated so I "assumed" I was getting a good reading. But as soon as I saw your post and realized my "assumption" I decided to use the old troubleshooting adage "Prove what you know". I removed the good resistor and it is measuring closer to 22 ohms now. Same ballpark, but always good to verify.
This makes the most sense. Matches the measurement I received from the good resistor when removed from board (22.4 ohm). The bad one "melted" in the middle but stayed intact, reducing in diameter by about 25%. Wattage is still an open question though.
actually i think it's red-red-black-silver, and the blue "band" may not be a band at all, but where the blue paint of the body color has been rubbed or compressed in the pick-and-place machine.
red-red-black would be 22 ohms, silver band 10% tolerance. i have some very similar resistors here, and the ones with blue paint appear to have a blue stripe, until you look closeley at them and you can see it's a wear mark. the ones that i have with grey body color appear to have a lighter grey stripe in exactly the same place.
it seems that the camera is "lying" when you see the black band as green, because the blue from the body color is bleeding into the band, because the picture isn't perfectly focused.. i blew this picture up real big, and there are green splotches in most of the shadows, as well as in the red bands on the resistors.
Thanks for all the feedback. I'll go with 22ohm 10% 1/2 watt and see what happens. It's a crap shoot whether replacing the resistors will fix the problem anyway, so if I'm wrong I'll just have to fork out $100 for a new board instead of 50 cents for a couple of resistors.
For some reason on my monitor all the resistors look like: Red, violet, green, silver, blue. You do the math. That's all three that look the same. The red band is much wider than the violet band and the other bands.
Solution:
Take more pictures from various different angles and post here. One picture is not always good enough for 3d items or for resolving colors. Pic's these days are cheap, almost nothing to take one and see it on the monitor, so take more, more more
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