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Need replacement capacitor but value not readable

Discussion in 'General Electronics Discussion' started by Zapper, Apr 8, 2019.

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  1. Zapper


    Sep 28, 2015
    I have a Eurotherm 91e Temp Controller that has blown a capacitor. I know it's a RIFA PME 2371Y 40/100/56C but the value has blown off.

    I can't justify taking it to Eurotherm as they charge a lot from memory. I can't find a schematic or photo of the circuit board. I posted already on the Eurotherm Forum but had no reply.

    Is there a practical way to work out the capacitance from the circuit board
  2. davenn

    davenn Moderator

    Sep 5, 2009

    HUH ??

    how about photo'ing YOUR board showing the capacitor

    would almost indicate 40uF 100V ... but seeing the type of capacitor would help confirm that
  3. Zapper


    Sep 28, 2015
    [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] 333[​IMG]

    I used these .0047uf RIFA PME 2371Y 40/100/56B on other Eurotherm models but I've never paid attention to what was in the 91e
  4. davenn

    davenn Moderator

    Sep 5, 2009
    thanks for the pix

    OK I would backtrack on my previous 40uF they would be so much bigger than what is present

    it appears to be a polypropylene / metalised ... polyprop for short

    I would suggest that in your first pic the PME 271 Y may be the value with the line below stating the tolerance and voltage rating etc

    but then 271 = 270pF would appear to be way too small a value for a PSU

    some one else may do a better interpretation

  5. Colin Mitchell

    Colin Mitchell

    Aug 31, 2014
    I would start with 100n X2 capacitor. (104)
  6. dave9


    Mar 5, 2017
    It's a (now Kemet, originally Rifa) class Y2, 250VAC, metalized paper, EMI suppression cap.

    The 40/100/56/C is just an IEC Climatic Category rating.

    There is no way to determine the capacitance value based on the markings remaining.

    They're available in capacitance range of 0.001 - 0.1 uF and lead spacing of 10.2, 15.2, 20.3, 22.5, 25.4. They may have dropped the 22.5 size at some point.

    If you look on the following datasheet you can narrow the range of possible capacitance based on the lead spacing, on page 5.
    If you measure the dimensions in width "B", height "H", and length "L" you might narrow the possible capacitance even further. I know, this will be hard to do with it swollen like a balloon so make your best guess.

    The same chart also shows new Kemet part #s though you wouldn't "need" to get this exact cap, another class Y2 250VAC (or higher) film cap that fits would work.
    Last edited: Jun 1, 2019
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