Confused about capacitor numbers

Discussion in 'General Electronics Chat' started by Korishan, Jun 29, 2016.

  1. Korishan

    Thread Starter New Member

    Jun 29, 2016
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    Hi everyone. First time poster here.

    I've tried looking for a capacitor for a UPS board I'm working on. I've found the MOSFET and resistor I need, but I can't find the capacitors.
    It is a square cube, green in color. The numbers on the capacitor is "22" stamped on the top (not sure if that means anything). On the side is:
    1817
    100
    9750

    I've figured that it's a MKT1817, 100V film capacitor. However, I can't figure out what that last number is for. And I've noticed there are different uF ratings for the MKT1817; unless I'm confused about something there.

    Can someone help me find what this is? Or can I just use any of the MKT1817 100v film capacitors in it's place?

    FYI: I'm adding the extra components to the UPS to help duty-cycle balancing and lower overall heat/wear-tear. There are 2 extra spots for 2 mosfets, 2 resistors, 2 capacitors.

    Thanks,
    Kori
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,908
    379
    If you look at the datasheet for MKT1817 you will see a table of sizes for different voltages & capacitances. If you measure the capacitor this will let you narrow down the possibilities.
    The '22' is likely the capacitance but whether it's 0.022uF or 0.22uF the size will tell you - and, yes, it will matter.
     
  3. Korishan

    Thread Starter New Member

    Jun 29, 2016
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    0
    Ok, thanks. That helps a lot :)

    At this datasheet here:
    http://www.vishay.com/docs/26032/mkt1817.pdf
    I notice on page 3 there are 2 listings for "22", which you mentioned earlier (either .022uF or .22uF). However, measuring gives me 4.5x9x7.2 which corolates to the .22uF. So that greatly makes things easier.

    Now, in the datasheet mentioned above, at the top of each page, it says "Not Recommended for New Designs, Use MKT370"
    MKT370: http://www.vishay.com/docs/28108/mkt370.pdf

    So, would it be recommended to just add the MKT370's, or should I try to get the MKT1817 since that's what's already in there? Or, should I just replace the MKT1817's with MKT370's across the board?

    Thanks again for your input
    Kori
     
  4. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    "9750" is probably the date code. It was made in the 50th week of 1997.
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    379
    For the two extra capacitors you can use either the original type, or the suggested type, whichever you can get easiest. The note about not using them for new designs is aimed at going into production with them. The other capacitors can remain as they are.
     
  6. Korishan

    Thread Starter New Member

    Jun 29, 2016
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    Thanks for all the input, it has helped tremendously.

    Now, if I understand the capacitors correctly I can replace with a higher Voltage rating if need be, correct? But what about the uF rating? Does that have to be exact, or could it be close? ie. .33uF or .30uF instead of .22uF

    Kori
     
  7. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Without details of the circuit, best keep to the same capacitance value but, yes, a higher voltage rating should be OK.
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    782
    It could end up being too big - but that should be the only problem.

    Its electrolytics that you have to select near the correct voltage - if you run them significantly under their rated voltage; the oxide dielectric thins - the voltage capability diminishes to what's applied and the capacitance increases.
     
  9. Korishan

    Thread Starter New Member

    Jun 29, 2016
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    Ok, got it, I think/hope :p

    Now, I do have another question about the MOSFET's I need.
    The MOSFET's have RFP40N10 on them. There is a replacement(ish) of IRF1310N, but confused a little about the compatibility.

    At this site, it says "Compatible Equivalent - The body and the findings coincide. but there are some differences in electrical lines.
    For example component has more functionality."
    Does that mean that it has the same pin-out and I can just solder it right into place?
    http://www.cross-parts.com/news/html/2008112001/0000077131.html
    (Or should I post this question as a new one?)

    Kori
     
  10. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Measuring the cap, is it not an option?
     
  11. Korishan

    Thread Starter New Member

    Jun 29, 2016
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    As noted earlier, I measured the cap to be 4.5x9x7.2 which comes to the .22uF.
     
  12. atferrari

    AAC Fanatic!

    Jan 6, 2004
    2,648
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    Sorry, I have should say measuring the capacity. That is what I would try upfront.
     
  13. ian field

    Distinguished Member

    Oct 27, 2012
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    To220 & TO247 MOSFETS always have the same pinout with the exception of a very small number of RF types.

    The 40N10 means 40A & 100V - for SMPSU applications; you have to check that the Ton and Toff on any substitute are equal or faster. RDSon is also important - there have been significant advances in getting RDSon as low as possible, so if you're replacing a modern part - many older designs probably won't do.
     
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