Electronics > Repair
Replacing unmarked SMD resistor
Bicurico:
Hi.
Die to a stupid mistake I had a short and it burned a SMD resistor. The PCB's top layer has a hole, but I found the traces and it should be possible to replace the burnt resistor and rebuild two traces.
I have a good board and I measured the resistor in circuit. It has 6 ohms give or take. Actually all resistors of the same size measured between 5 and 6 ohms. Unfortunately they have no markings, as opposed as other resistors on the board, which are flatter. These have the typical 3 digit codes.
I assume that the burnt resistor was a thick type carbon resistor.
My questions to the pro's:
Can I replace this SMD resistor with a normal 6 ohm resistor, not a SMD One, for easier soldering and availability?
Does it make sense to measure a resistor, as opposed to a capacitor, while in circuit? I would get it should be ok.
How can I know what the thickness of the wire should be? The trace that burned was fairly thick, but then it had a hole to connect to the middle layer (still working), which is tiny.
Thanks!
Swake:
You cannot trust an in circuit measurement of a resistor to have its real value. Whatever is in parallel with that resistor is going to mess up the reading. You'll have to remove the good resistor to measure it out of the circuit. This really is the only right way.
You can generally replace an SMD resistor with a through hole one, but it is not going to be an easier soldering at all.
Make pictures of both good and bad boards. Chances are the things you're looking at are not resistors.
Bicurico:
I attached two pictures.
I would suspect this to be either a resistor or a fuse.
Swake:
That is a capacitor.
Finding the value is going to be tricky unless you are willing to unsolder the good one and have a good C-meter. The value might not be all that important given how it is connected with the 4 legs of that chip nearby. What is that chip? I can't read from the pictures. I think it is a MOSFET and that this is part of some power supply.
kripton2035:
it looks more a capacitor than a resistor ...
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