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What are these black things that have come loose?

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bleeP

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Hi!
What are these:



that belong here:




If these can be recognized by someone, i'm also looking for advice on repairing. Is there any possibility to join them back where they belong, or do i need new ones (in that case i need assistance on what to buy).
 
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betwixt

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They are EMC filters, basically a loop of wire with two ferite beads, one on the up side and the other on the down side. You can buy them or make a replacement yourself. I would suggest before buying anything, you carefully snap the bridge between the two barrels and see if you can pull the wire out of them. You can then make a new filter by threading a new wire in it's place, leaving enough excess length to solder the ends back into the PCB.

Brian.
 
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bleeP

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Thanks for the information. I would like to clarify something because i don't have much experience with electronics and not very familiar with terms. Do you mean that if i break one of my "black things" i can find 2 of these inside:
thb_FeUKW_pf2.jpg
And the i could remove the wire and put new wire in there?
 

Mattylad

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Yes.

Although it's not exactly the same as the one in your picture, it will just be a pair of tubes with a single hole in.
2 ferrite tubes with wire running through it, it's purpose is to link 2 bits of board (input from what looks like a USB socket) to the board.
You could just link them out ut it would be better to include the ferrite so the perform the original purpose.

Pull the wire out of them (twist to break the black stuff, pull out wire, clean them) and replace it with more wire (resistor legs etc).
 
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bleeP

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Thanks a lot for both of you. Just one question, what kind of wire should i get for replacement? Copper wire?
 

betwixt

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Yes, any copper wire will do. As Mattylad suggested, you can use the cut-off legs of resistors if you have any. Obviously, the wire has to be solderable to connect it to the board again so tinned copper wire would be best. The black coating on the broken parts is just epoxy resin to stop the ferrite beads rattling if you shake the machine!

Their purpose is to stop unwanted signal leakage in or out of the socket and the cable plugged into it. Often they are needed so the machine passes the strict EMC regulations that set the limit for how much interference it is allowed to radiate. They also form an electrical bridge across a section of the board which may be used to allow copper traces to run underneath it. If you are confident nothing will be upset by interference leakage (buzz and whistles on nearby AM radio for example) you can just link a wire across without fitting the beads at all. It may break the regulations but speaking practically, the level of interference is likely to be extremely low and despite bearing conformity labels, quite a lot of other equipment never meets specification from new.

Brian.
 
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