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Help needed with capacitor replacement

Discussion in 'Solid State' started by Vaylo, Nov 9, 2018.

  1. Vaylo

    Vaylo New Member

    Messages:
    8
    Hello guys,

    time has come to replace one of the filter caps in my tuner and amplifier. Please see below scheme from the service manual, it's marked C901.

    [​IMG]

    My expectation would be to place an X2 cap here but when i look at the existing cap there's a 'Y' letter stamped on it, which confuses me as then I would expect one of the leads to be connected to the ground rather than to a transformer:

    [​IMG]

    It's RIFA, type PME265MB510, unfortunately I cannot find any datasheet for it to be sure whether it's an X or Y.

    In case it's an X-type would this be a correct replacement?
    https://www.tme.eu/en/details/mkpx2...olypropylene-capacitors/kemet/r46ki21005001m/

    Many thanks in advance for your help.
     
    dlucy likes this.

     

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  2. mbz

    mbz Super Member

    Messages:
    2,186
    Location:
    Melbourne, Victoria
    The cap is a snubber cap used to prevent arching when the power switch is turned on. The (larger) filter caps
    will be on the other side of the transformer. The cap looks fine to me, why do you want to replace it, it won't improve sound quality.
     
  3. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,778
    Location:
    Fort Dodge, Iowa
    There is probably nothing wrong with the Rifa snubber cap.

    Your Kemet selection would be fine.
     
  4. Vaylo

    Vaylo New Member

    Messages:
    8
    Hi,

    Yup, my bad, you're right, english is not my primary language :)

    Unfortunately it's totally cracked in the tuner (which does not even turn off when you push the power button). I think the one in the amp will follow soon. They are almost 40 years old.

    Many thanks for quick replies, I'll go with the Kemet replacement.

    Thank you guys.


    [​IMG]
     
  5. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,778
    Location:
    Fort Dodge, Iowa
    LOL Thats not good..
     
  6. mbz

    mbz Super Member

    Messages:
    2,186
    Location:
    Melbourne, Victoria
    Yeah replace the cap however it is not responsible for failed power-on. The snubber will either fail short or open, neither will prevent
    power up. Double check fuses.
     

     

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  7. mbz

    mbz Super Member

    Messages:
    2,186
    Location:
    Melbourne, Victoria
    F911, F912,F901 transformer also has a thermal fuse, maybe check for AC on secondary, if no AC check resistance/continuity of
    secondary be measuring resistance at power plug active/neutral pins, power switch ON.
     
  8. Vaylo

    Vaylo New Member

    Messages:
    8
    Hi,

    there's no problem to turn the machine on. I wrote that the issue is it does not want to turn off :) Only unplugging the socket helps.
     
  9. mbz

    mbz Super Member

    Messages:
    2,186
    Location:
    Melbourne, Victoria
    Apologies, english is not widely spoken/understood in Australia.

    This is good news, means the cap has failed short, simple fix...
     
  10. Vaylo

    Vaylo New Member

    Messages:
    8
    Thanks again for all the replies. Now a question about those large ones (power supply filter caps). I'd like to replace them as they are 40 years old. Considering their capacitance which is 6800uF, minimum voltage of 40V and lead pitch of 12.5mm it seems I only have three choices (with THT mounting):

    Nichicon UVR: general purpose cap, 2000hrs/85C degrees, ripple current 3900mA, 63V
    Nichicon UVZ: general purpose cap, 1000hrs/105C degrees, ripple current 2800mA, 63V
    Nichicon UFW: "audio grade" cap, 2000hrs/85C degrees, ripple current 3500mA, 63V

    Which one should I go for?

    Btw we talk about Onkyo A-15 here, 2x25W @ 8 Ohms max output, a pretty lowendish amp but I love it.

    Thanks.
     
  11. Binkman

    Binkman AK Subscriber Subscriber

    Messages:
    6,543
    Location:
    Chapel Hill, NC
    Greetings; Is "6800uf" a typo? Your choices don't match the rated uf.
     

     

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  12. Vaylo

    Vaylo New Member

    Messages:
    8
  13. Binkman

    Binkman AK Subscriber Subscriber

    Messages:
    6,543
    Location:
    Chapel Hill, NC
    sorry my error not reading your post correctly.
     
  14. dlucy

    dlucy dlucy67 (Doug) Subscriber

    Messages:
    1,983
    Location:
    Philadelphia, PA
    It is definitely a safety cap, e.g. X2 or Y2. There is a description of the classes here: https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/

    The schematic doesn't show the cap going from line to ground, so I'd guess it is supposed to be a X class cap.
     
  15. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
    1,732
    Location:
    Victoria, Australia
    Those Rifa safety caps are notorious for failing like yours has, l have seen quite a few myself.

    In regards to your filter caps, how about these Nichicon LS snap in's, they have lower impedance and higher ripple than the ones you mentioned. You can easily "tweak" the 10mm leads to fit your 12.5mm spacing.

    https://www.tme.eu/en/details/lls1j682melb/85c-snap-in-electrolytic-capacitors/nichicon/

    I am guessing you have enough room to fit 30mm diameter caps?
     
  16. Vaylo

    Vaylo New Member

    Messages:
    8
    Hi,

    I was considering those as well. As long as it is perfectly 'safe' to add leads to them I'll for sure go with those. And yes, there's plenty of room for them as the old ones are like 40mm in diameter.

    Thanks very much.
     

     

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  17. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
    1,732
    Location:
    Victoria, Australia
    Are these just going through a standard board thickness, ie approx 2-3mm? these snap in leads will have plenty of length for through hole fitment. Depending on what caps are originally fitted you may have to drill out holes/traces in board to 1.0-1.5mm.
     
  18. Vaylo

    Vaylo New Member

    Messages:
    8
    Yeah the board is thin. It's like 2mm at most. I just looked in the datasheet and those leads are 4mm long. So maybe I will not need to drill any holes or add leads as I only need to go like 1mm to each side to fit them in the original holes. Carefully bending them may do the trick.

    [​IMG]
     
  19. Oldsansui441

    Oldsansui441 AK Subscriber Subscriber

    Messages:
    1,732
    Location:
    Victoria, Australia
    Yes you are correct, they should be fine, l have done this before with no issues. Probably a good idea to add a little glue under base of new caps for stability.
     
  20. OMGCat!

    OMGCat! AK Subscriber Subscriber

    Messages:
    3,142
    Location:
    El Sereno, CA
    Many times the through holes are pretty big for filters and you'll find more than enough room to fit a 10mm spacing where there was a slightly wider spacing originally.
     
    Oldsansui441 likes this.

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