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Comments on What are these mystery components (one of wire coil, another labeled "100-10L A9")?

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What are these mystery components (one of wire coil, another labeled "100-10L A9")?

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I have here an acre-counter or crop counter device like the lykketronic shown below, using two AA batteries. It arrived without working. lykketronic acre counter

Upon opening its case, I found that the PCB is missing two components, and the area where these components were is scratched, as though someone removed them carelessly.

Here is a photograph of the main PCB. The top part (cropped) is just the LCD.

PCB entire

And a close-up of the corner missing the components.

I was able to find another identical device, and the components are intact. One is a coil of wire on a black spool with a rectangular top. The other is a rectangular box labeled "100-10L A9". Here is a general view:

sane PCB

And again the close-up, including the mystery wire coil component: wire coil component

Is this wire coil a filter of some sort? An impedance? What does it do?

And what is the black box to its left? It looks like an SMD capacitor like this one at mouser, but I don't know how to interpret its label.

I am hoping to either replace or re-make the components to restore the PCB.

identification repair
posted 9 months ago
9mo ago by Nick Alexeev‭
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Conrado‭
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4 comment threads

It arrived without working (2 comments)
[meta] component ID questions and repair questions (1 comment)
What's the output of the SOT-89 chip with the 331 marking? (2 comments)
What's connected to the [-] and [+] throughole pads? (4 comments)
What's the output of the SOT-89 chip with the 331 marking?
Nick Alexeev‭ wrote 9 months ago
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Conrado‭ Check the output of the unidentified 331 chip on the undamaged unit. Probe the voltage at the middle pin, and at the other tantalum capacitor (the East-West one). It may be a boost switcher. That would explain two things: the connection of the inductor, the diode between pins 2 and 3. If you’ve got an oscilloscope, check if any of the pins of the 331 chip are switching (pin 3 raises suspicion).

Conrado‭ wrote 9 months ago
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Nick Alexeev‭ Oh, I didn't know enough to know what I don't know yet... I didn't think to check the voltages one the intact device, and I don't have it in my hands; I only borrowed it to get the pictures of the missing components. I've ordered a capacitor to specs as explained by Lundin and a 10uh inductor on *bay; where I live in Chile postage takes about a month from anywhere, so when they get here I'll have a try at it, and then I may be able to update this post with that information about the 331.