Electronics > Repair
Replacing unmarked SMD resistor
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shapirus:
I doubt that a ferrite bead would measure as high as 6 ohms on the working board. I'd expect it to be near-short.

It could also be an inductor.

Really the best way would be to desolder it from the working board and find out what it is by measuring R, L, C.

Another option (but without guarantees) would be desoldering the parts that look the same near the burned one on the damaged board and testing them. They might be the same, and if they measure the same on the working board (even in-circuit), that could speak in favor of it.
kripton2035:
even an inductor would not measure 6 ohms ?
Bicurico:
That might have been a mistake, I just measured in-circuit with my Uni-T 61E in Ohm mode. Perhaps there was some oxide layer or dirt. I will measure that again.
Please note I measured the OTHER similar looking components (probably/hopefully ferrite beads, also).
The good board is in another working device and I don't want to risk breaking it - I already caused two misfortunes in two weeks...

shapirus:

--- Quote from: Bicurico on January 06, 2025, 04:22:26 pm ---Please note I measured the OTHER similar looking components (probably/hopefully ferrite beads, also).

--- End quote ---
I think a decent starting point would be to carefully desolder one (or better more) of them on the damaged board and measure them out of circuit. If you don't have an LCR meter, then measuring their resistance and capacitance with a general DMM can already tell us something useful.
Bicurico:
I have some further questions:

Imagine I do have a compatible replacement SMD ferrite bead.

1) How would you tackle the burned area? Leave it as is or fill it with hot glue or resin?
2) How would you repair the broken pad? Try to use lots of flux and apply solder in the hope it will make contact with the hole (which is still contact) or would you solder a new wire from the SMD ferrite bead to the pad of the connector?
3) What are the chances that the repair would end up stable and lasting, without risking damage to the board that is powered by this pad of the connector?

I know these are vague questions, but I would like to hear your opinions based on experience.

Thanks!
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