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Broken Battery Drill Charger.

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My drill charger was dripped and does not work now. After looking inside I can see damage. Two coils mounted on a small plastic former have come away from the P.C.B. The wires are hair thin and I am not confident in re-soldering them back. On the P.C.B. the mains flex connects to terminals and a yellow "capacitor" (guessing here, marked .22k, 300V a.c. 40/105/21.  connects across them, that is o.k.. The "capacitor" is connected parallel to a resistor, perhaps to discharge it, then the two small coils are located. After the coils there are 4 diodes, perhaps a bridge rectifier, then the circuit goes into the automatic charging section.


Are the coils essential, or can I just shunt across them? If I do just shunt across them will next door's radio or telly misbehave?


Thanks,


Z.
  • 0
    Sounds like you have correctly identified the RFI filter or RF "choke".


    Choke is between mains and the bridge rectifier, and may double as the fusible element in the value engineered design.

    Yes if you omit it, it will probably run, and charge things OK. It is however not likely to meet the letter or the spirit of the EMC regs without it, and radio reception and broadband use nearby may be a corrupted. 

    (overhead 'phone lines carrying ADSL or VDSL act as rather indeterminate antennas, and the pick up of fast switching spikes and sensitive broadband modems to not co-exist well.)

    After all if it did not need the filters to pass type aproval,  it would not be there

    I might leave the filter out as a quick test to see what else is broken. Longer term, can you unwind one turn of the wire. to form a new end, or fit another easier to handle filter externally or in-line.
  • 0

    mapj1:

    Sounds like you have correctly identified the RFI filter or RF "choke".


    Choke is between mains and the bridge rectifier, and may double as the fusible element in the value engineered design.

    Yes if you omit it, it will probably run, and charge things OK. It is however not likely to meet the letter or the spirit of the EMC regs without it, and radio reception and broadband use nearby may be a corrupted. 

    (overhead 'phone lines carrying ADSL or VDSL act as rather indeterminate antennas, and the pick up of fast switching spikes and sensitive broadband modems to not co-exist well.)

    After all if it did not need the filters to pass type aproval,  it would not be there

    I might leave the filter out as a quick test to see what else is broken. Longer term, can you unwind one turn of the wire. to form a new end, or fit another easier to handle filter externally or in-line.




    Thanks Mike. I will try to get the charger working with the choke shunted initially to see if the charger works. Then replace it if possible. The circuit does have a 3.15 Amp soldered in fuse at the supply part of the P.C.B. I would expect nothing less of Hitachi.


    Z.

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