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ZNR Help Please

Discussion in 'General Electronics Discussion' started by Mickey13, Apr 5, 2013.

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  1. Mickey13


    Apr 5, 2013
    I have an older Power Filter. Inside are left and right side mirror images for the power input.

    On each side is a ZNR 20K201U 9w resistor. On one side the ZNR resistor completely blew out. The unit also blew a protector which I replaced.
    I did not replace the ZNR I removed it and the unit is working fine drawing clean voltage from all sockets. Not knowing alot about these:
    Question: 1. Do I have to replace the ZNR?
    2. This is really hard to find this ZNR 20K201U 9w, can I replace it with a different
    value like ZNR K201U with a 1 3 at the bottom. or a znr 14k201u 39

    I thank you in advance for your help with this.
  2. Electrobrains


    Jan 2, 2012
    That is not a resistor, it's a varistor, preventing your circuit from over voltage.
    Probably that fellow had to die to save whatever was behind the filter (a very Christian concept).

    The number "20" usually stands for 20mm disc size. The size also specifies how much energy the varistor can absorb.

    "201" should tell you the voltage and on that spot I have seen a bit of confusion, which kind of voltage is specified.

    If the filter is specified for 110V AC power lines, the varistor code makes sense as a 200VDC Varistor. The maximum operating voltage of such varistor is specified at 130VAC.

    I have mostly worked with Epcos (Siemens) varistors and the type you would use as replacement would be S20K130 (only referring to the Epcos code!)

    You should definitely put in a new varistor in that place, or your filter will not protect you next time.
    Also the size should be the same.
    Last edited: Apr 6, 2013
  3. Mickey13


    Apr 5, 2013
    ZNR Information

    Thank You very much your information was helpful.
  4. brevor


    Apr 9, 2013
    Look for a V130LA10A it is a common replacement.
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    I guess it should be pointed out that there are a plethora of voltages associated with varistors, (working max AC and DC voltage, breakdown AC and DC voltage, limiting voltage, etc.) and the specs can use almost any of these in the part number.

    In the original part number 201 means 20 x 10^1 (200) and apparantly represents the maximum DC working voltage.

    I haven't checked, but if the replacement suggested by brevor is correct, the 130 directly refers to 130V AC (RMS). (same is true of the one electrobrains suggested).

    130*1.414 = 182, and that's less than 200, bit it may represent a working voltage rather than a maximum voltage..

    There are 2 ways to determine if one is suitable. The first way is to look at the datasheets and see if the various voltages etc are similar.

    The second is to know what devices are typically used for your mains voltage, and use the size as a rough (but not too rough) estimate of energy rating.

    Note sure if this post is at all useful.
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