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quinnvanorder
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I am trying to repair this device and have determined that the issue is with this melted resistor... In order to find the correct replacement i need to determine specifically what resistor this is.
Although I am not familiar with this aspect of electrical engineering, I am familiar with electronics. I have built several pc's and have done minor soldering repairs and such. I always disconnect the power before running and I use an insulated screwdriver to bridge the capacitor to prevent any danger to me.vk6kro said:That plug is usually used for mains voltage appliances, which means you probably shouldn't be doing this.
Do not touch any part of the circuit board if power is applied.
How do I check for a capacitor being faulty?It is possible for these plugs to make a bad connection, but that would not normally cause a resistor to burn out.
The capacitor next to the burnt resistor could be faulty, or it may just have got hot from the resistor next to it.
What is the function of the circuit board with the burnt out resistor on it?
Ok thanks, I will check this out tomorrow and post results. Thanks for the help!The large black thing next to the resistor looks like a power transistor or possibly a triac.
If you test the resistance between the leads of this, then none of them should be less than, say 300 ohms.
If you find any with resistance less than this, the transistor may be faulty.
Thats the interesting thing, this device actually works for a bit. When I plug it in, it let's me set the temperature, but it cuts out when it exceeds roughly 100 degrees. As long as I let it cool off, it will work again. My hope was that I can get a mostly accurate measurement when it is cool. Also I the multimeter I am borrowing is not cheap so hopefully it can get an accurate read.Studiot said:I am going to stick my neck out here and suggest another analysis.
Firstly the resistor, although obvously overheated may well not be destroyed, because it looks like a wire wound power type and the wire appears intact. If so, this will not have changed its resistance on cooling. Obviously the protective ceramic coating has burned away so the componeents needs replacing.
This resistor is likely to have quite a low value, difficult to check accurately with a cheap multimeter.
Are you referring to the black thing next to the burned resistor?The power controller?
I can't see any rectifiers so this is likely a thyristor/triac. Does it have any markings/ letters. Post these. It may well have failed. Multimeter check on these are unreliable.
Well I'd say that the load element has overloaded the controller circuit for some reason. Perhaps it has gone (partial) short circuit.
Are you referring to the black thing next to the burned resistor?
BTW, that is a VERY common plug type. If still possible, you might consider undoing your soldering job and simply picking up a cable at an electronics surplus shop or off one of uncountable dead appliances.quinnvanorder said:Another theory for outside interference that could have damaged it: This device used a plug that looks like this
Antiphon said:I am 90% sure of the following but I write it as if I am 100% sure. You need to confirm with a meter.
The large capacitor is a series ballast. It has most likely gone bad. It works by acting like a large lossless voltage drop at 60 Hz. The black cube is a three-terminal voltage regulator which still works and is powering the micro. It has a built-in thermal shutdown which is why it quits.
Im not sure where the power resistor sits but if post the schematic it might confirm the above speculation.
a heating element. as you can see here, this heating element is placed in the glass and metal tube, with the thermal sensor resting immediately behind it, on top of its wires.I have desouldered the burnt resistor(Pictures), and in an hour or two I will be able to post the results about what it reads..jim hardy said:what does this thing control?
what connects to those metal tabs?
vk6kro said:The last photo shows an F1 on the board, and assuming this is a fuse, I can't see it on the other side of the board. Maybe that is supposed to blow if the capacitor fails, except it may have been bypassed in the rewiring effort.
Studiot said:The rectifier is the object to the right of the legend on the board R13 and D4. It has a number beginning 1NXXXX. Filling in the XXXX will identify it. You do not need to desolder it to test it. Just use the ohms range on the multimeter to check the it has high resistance with the leads connected one way across it and low resistance with the leads connected the reverse way round.
I found that there is in fact no fuse on this board, nor was there. The board came with the power wire soldered straight to where the fuse should go. Should I/could I put a fuse into prevent this in the future, and what type?vk6kro said:The last photo shows an F1 on the board, and assuming this is a fuse, I can't see it on the other side of the board. Maybe that is supposed to blow if the capacitor fails, except it may have been bypassed in the rewiring effort.
vk6kro said:Can you try to read all the writing on the "3 wire regulator". I don't think we know for sure that is what it is.
E
NXP
TJA0906B7
You could consider a fuse later if this ever gets fixed.
Q: How can I tell if a resistor has overheated and melted?
A: You can usually visually inspect the resistor for discoloration, warping, or melting. Additionally, the resistance value of the resistor may have changed if it has overheated.
Q: Why did my resistor overheat and melt?
A: Resistors can overheat for a variety of reasons, including high voltage or current passing through them, excessive ambient temperature, or incorrect installation or usage.
Q: What do the color bands on a resistor mean?
A: The color bands on a resistor indicate its resistance value, tolerance, and sometimes its temperature coefficient. These color codes can be decoded using a resistor color code chart.
Q: Can I still use a resistor that has overheated and melted?
A: It is not recommended to use a resistor that has overheated and melted, as its resistance value may have changed and it may no longer function properly.
Q: How can I determine the type of resistor that has overheated and melted?
A: The type of resistor can usually be determined by its physical characteristics, such as its shape, size, and construction material. You can also refer to its documentation or markings on the resistor itself.