Author Topic: Repair this part - FB  (Read 370 times)

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Offline almamater

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Repair this part - FB
« on: April 09, 2021, 10:11:02 am »
Hello.

Recently my LG Mini Hifi XA14 stopped working, the problem:



The +5V input (from Power Supply) had burned! So, i clean everything and put two wires (just for test) and with other power supply (ATX) it worked!

So, i check the original power supply, changed one diode and capacitors, and now the voltages are OK



And i tested all again with the original Power Supply and works!

But now i have one doubt, the 2 two components "FB" at the entrance of the + 5V exploded:


So I researched and they would be "Ferrite Bead", in the service manual (page 38) is the following:


what kind of protection can i put there now? What type and value of ferrite can i use? I only have this kind off ferrites here ;D :
 
« Last Edit: April 09, 2021, 03:45:47 pm by almamater »
 

Offline almamater

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Re: Repair this part - FB
« Reply #1 on: April 12, 2021, 10:33:28 pm »
Can i use two "330uh 400ma" ? It's what i find near me..
 

Offline perieanuo

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Re: Repair this part - FB
« Reply #2 on: April 13, 2021, 08:15:43 am »
or this:
 

Online Ian.M

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Re: Repair this part - FB
« Reply #3 on: April 13, 2021, 09:13:37 am »
No.   You need to find the specs on the ferrite beads and at a minimum troughly match the DC resistance.  Is there a BOM in the service manual you can get a full part number from?
 

Offline almamater

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Re: Repair this part - FB
« Reply #4 on: April 13, 2021, 09:41:46 am »
 :-\  I only can find the service manual (link) but it only have this reference "300RH" on page 38.

Its possible remove and check the values from another one?
 

Online Ian.M

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Re: Repair this part - FB
« Reply #5 on: April 13, 2021, 09:56:29 am »
"SECTION 4 ........REPLACEMENT PARTS LIST" is missing from the manual you linked.  Try to find an alternative copy that has that section.

There's no need to remove any from circuit to measure them, simply unplug PN1/CON9 to isolate one end of them.

They've obviously acted as fuses (poor ones as they burnt the board) and it would be desirable to maintain their over-current protection.  If you can find some slip-on type ferrite beads as usually used for through-hole applications, you could transplant two of the good '300RH' ferrite beads from 'MGND' pins of the header, and replace them with slip-on ferrite beads on wire links.
 


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