# Replacing an inductor, but there are so many and don't know which one is the correct

#### ragarcia

Joined Sep 3, 2021
3
Hi,

I am trying to revive an equipment used for apnea monitoring. It uses 2 AA batteries, but doesn't work.
I opened it up and one inductor had a crack and makes a buzzing noise. It appears to be part of the power supply circuit.

The marking on the inductor is 4R7 1U.
See image, the tape is just to keep the broken corner attached.

When I search for it, a whole family of inductor appears. I don't know which one is correct.

Thanks,
RG

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#### Ian0

Joined Aug 7, 2020
3,761
Superglue it!
If you want to replace it, 4R7 means it's 4.7μH. Get one that's the same physical size and it will work.

#### ragarcia

Joined Sep 3, 2021
3
Superglue it!
If you want to replace it, 4R7 means it's 4.7μH. Get one that's the same physical size and it will work.
Thx for the info.
So, basically the main thing is getting the same dimensions (size).

I am checking some that list : inductance - 100KHz, 1.0V... 4.7 and others list 0.1V @ 10KHz .
Does this values make any difference?

Thx

#### Ian0

Joined Aug 7, 2020
3,761
To be perfectly honest, you're trying to achieve the same amount of energy storage, and the same saturation current, but energy storage is pretty much proportional to the amount of magnetic material, and saturation current is proportional to cross-sectional area and number of turns.
But when all said and done, both these things depend on how big it is.
If they measure the inductance at 1V @100kHz, or if they measure it at 100mV @ 10kHz, it will be about the same for an inductance of 4.7uH. If the inductance were much larger, then it might work better at 10kHz than it would at 100kHz, but a 4.7uH inductor should be good for a few MHz, so 10kHz or 100kHz should make no difference