Substituting a 25 volt cap in place of a 6.3 volt one

Discussion in 'Pioneer Audio' started by Stevescivic, Sep 14, 2017.

  1. Stevescivic

    Stevescivic Active Member

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    I failed to order a replacement 220uF 6.3 volt cap from Mouser for the function switch board on my SX-1050.

    I had some spare Nichicon UPW series 220uF 25 volt 105C rated caps. Is it okay to use that in place of the original cap even though the new cap is 25 volts?

    Thanks
     
  2. zebulon1

    zebulon1 This summer heat slowed me down. Subscriber

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    You can always go up in voltage.
    Most of the time the newer higher voltage caps will be the same size as the old originals.
     
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  3. Stevescivic

    Stevescivic Active Member

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    hey Zeb, that was what I thought as well but I wasn't confident jumping so much in voltage. Had I dropped in a 10 or 16 volt cap then no biggie but 25 volts could potentially cause too high of a ripple current that would in theory damage other components down stream no?

    In any case I replaced the cap with a new UPW cap so I guess the only way to tell is to fire it up on DBT!
     
  4. zebulon1

    zebulon1 This summer heat slowed me down. Subscriber

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    The 6.3v's are harder to come by. Go to 10, 25 or 35 volts.
    You'll be fine. Make sure you have it in the correct polarity. That's it.
     
  5. Stevescivic

    Stevescivic Active Member

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    okay, polarity definitely is correct and the cap I used fit perfectly.
     
  6. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    I tend to avoid using 6.3V or 10V replacement electrolytic capacitors if possible, (barring size limitations), preferring to use 16V or 25V.
    In theory at least, a 6.3V electrolytic will work just the same as a 25V electrolytic, the voltages are just a rating, it's the applied voltage 'in circuit' that matters.
     
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  7. Leestereo

    Leestereo Super Member

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    The ripple current is function of the capacitance value, not the voltage rating: increasing the capacity lowers the AC ripple. Also, it is recommended to use capacitors rated at least 16V or 25V since lower voltage rated capacitors do not perform as well and are not as long lived (@ConradH has discussed this in this thread: http://audiokarma.org/forums/index.php?threads/bought-some-silmic-iis-just-because.490633/).
     
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  8. zebulon1

    zebulon1 This summer heat slowed me down. Subscriber

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    Also:
    Another voltage rating consideration I realized only recently, is not only to cover the voltage in the circuit but might give some consideration to a runaway circuit supply.
     
  9. gadget73

    gadget73 junk junkie Subscriber

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    I don't think any of the parts I put in my SX-1500TD variant were under 25v, some of the originals were rated 6.3v. One was rated I think 3.3v. Hard to find values in voltages that low but in the old larger physical sizes. They do exist in teeny caps but the lead spacing doesn't work on 1970s electronics.
     
  10. john stumpf

    john stumpf AK Subscriber Subscriber

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    a few months back i was trying to get feeble mind around capacitors with regards to low impedance/ low leakage and audio grade types and the pro's and cons in older designs. in this seemingly endless stream of data.liberally seasoned with opinion came one alleged kernal of wisdom from a NICHICON DESIGN ENGINEER. that E caps are happiest at 50- 75% of their rated voltage. i just read this stuff and dont pretend to know one way or another! but i thought i'd mention it to see what greater minds than myself had to say as it seems to bear directly to what the o.p.was asking. ive subbed higher voltage caps and everything appears to work just fine. but it does make me wonder.
     
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  11. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    Well done for bringing this up. ;) It seems these days you can take somewhat greater liberties with voltages. Maybe modern capacitors perform better over a wider voltage range, or maybe other considerations, (see below), now over-rule what was important when that statement (by The Nichicon engineer), was made. Personally I try to adhere as closely as possible to those limits but alter my views when it comes to modern low voltage electrolytics, (less than 10V), which I understand, even when 'new' generally have a short and unreliable life.
     
    Last edited: Sep 15, 2017
  12. Stevescivic

    Stevescivic Active Member

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    This is interesting banter. Didn't think my simpleton question would garner the attention that it has. One thing is for certain is that I'm glad my impromptu substitution worked out in my favour from a "suitable and reliable part standpoint".
     
  13. Stevescivic

    Stevescivic Active Member

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    BTW, even though my recap jobber on my first SX-1050 is complete I am now wondering what purpose does this lone capacitor do on the tone input selector board?
     
  14. Hyperion

    Hyperion Roobarb & Custard Subscriber

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    If you mean C1 on AWS-094, it looks like damping for the Signal Meter.
     
  15. SaturationPt

    SaturationPt AK Subscriber Subscriber

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    These electrolytic capacitors are designed around specific operating parameters, one of them being the voltage. You can always use a higher voltage capacitor, but IMO it isn't always good practice and beside that, ... why?

    When I select a capacitor for a circuit, I select it based on the maximum voltage in use. The capacitor is designed to operate at that voltage, and as we can see with these old beasts heat is what shortens their life, when they're shot they're shot no matter how much higher their rating is than their actual use. If it worked fine for 40 years and the technology has improved, ...

    The higher voltages need to have more or better dielectric to prevent breakdown at the higher voltage, and might not have the same reactance at significantly lower voltage.

    A 100v / 220uF capacitor is rated at 100v nominal, and is 220uF at that voltage, ... not necessarily at 6.3v. This is its rated operating voltage, not its maximum.

    If you take out a 6.3/220 and can get a quality 6.3/220, use that. If you can't, especially in a power application, no harm in increasing slightly.

    I would not recommend changing voltage significantly in signal path nor in filters, I was always very careful in designing filters and looked at capacitors very carefully. Changing to a much higher voltage WILL change your filter.

    I know that there are many here who routinely replace all electrolytics with at least the next voltage rating up, not sure what they think that they're gaining, and I know that I'm turning this into a debate with my opinion. However, lets see measured data that shows why you should change the rating from the Engineers' original design. Anyone?

    Next feel free to ask why many people also somehow feel that the Engineers put smaller value main filter caps in amplifiers than the optimum value for highest output, ... here's a hint: THEY DIDN'T! They put in the best capacitors for the musical performance of their amplifiers.

    Now I realize that there are BPC amps out there, the lowest-bidder crap from recent years, but this thread is about the SX-1050.
     

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