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

Stevescivic

Active Member
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
 
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!
 
I tend to avoid using 6.3V or 10V replacement electrolytic capacitors if possible, (barring size limitations), preferring to use 16V or 25V.
25 volts could potentially cause too high of a ripple current that would in theory damage other components down stream no?
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.
 
...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?...

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/).
 
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.
 
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.
 
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.
 
wisdom from a NICHICON DESIGN ENGINEER. that E caps are happiest at 50- 75% of their rated voltage.
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.
 
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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".
 
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?
 
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.
 
I know it's 6 yrs late....................However, looking at the capacitor rated voltage and the circuit voltage, Pioneer tended to run the circuit voltage at or 1-3 volts below the rating on the caps or the reverse they spec'ed caps at 1-3 volts above circuit voltage (bean counters!). With the attendant rise in wall voltage today it makes sense to bump the voltage up as the circuit voltage is quite possibly higher than the voltage rating on the capacitors. This can conceivably place the running voltage in the 50%-75% of the caps rating as noted by the aforementioned Nichicon Engineer.
 
That and the fact that so many 6.3V caps are bad, no matter what the uF rating. Especially true in "always on" circuits for remote controls, etc. I replace with 10V even though the 5V logic circuits are always regulated.
 
I've been reading some people's thoughts on this and think I will try and stay closer to the original voltage rating on Ecaps, no more than doubling if possible.

A few things though; say you replace a 2.2uf 16v Ecap, with 2.2uf 63v film cap - in that case it should be fine right? The film cap has no electrolytic formulation in it designed to run at a certain voltage. One other spot I see trouble is staying within these limits for the main caps, often I find I need to go up quite a bit in voltage to find a pair that fits the clamps. For instance I think I had some that were rated 35V and I ended up having to go all the way up to some 80V ones to fit the clamps. I know I could put foam around them to act as a spacer for smaller caps, but I have not. Any opinions on how much this rule applies to main caps compared to small circuit caps?
 
Film caps have other issues I think -- I can't imagine that a coke can sized 400V film cap will act exactly the same way a tiny 50V film cap in circuit -- there will be different deviations from the "ideal" capacitor, including resonance peaks and inductance I suspect, although I'm not an EE by any means. 16V to 63V would be fine, most film caps aren't made in low voltages anyway (and neither are small value electrolytics), probably due to issues in manufacturing them with through-hole leads. They would be very small....

For the main filter caps, losing form results in more leakage, and if the applied voltage is insufficient to "re-form" the caps in a reasonable time, they will get hot, reducing their life. Short fat caps would be better than much higher voltage, but we are stuck with what we can buy and I appreciate the desire to keep them clamped well, especially if they are screw cap or open bridged where falling out will cause shorts. Personally I'd 3D print up an solid spacer ring, but that's me.
 
That and the fact that so many 6.3V caps are bad, no matter what the uF rating. Especially true in "always on" circuits for remote controls, etc. I replace with 10V even though the 5V logic circuits are always regulated.
ConradH has mentioned that the low voltage caps are the only ones he finds consistently worn out in vintage gear and replaces most under 16V with 25V minimum. Along with Larry’s comment about line voltage going up a bit over the decades, seems going up is a good idea.

I'm not too concerned with low voltage caps getting replaced with higher voltage and group all the 3.3-25V caps of the same value to allow a larger purchase discount at 10/25/50 or 100 pieces as I don’t stock hundreds of caps.

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
we differ on this issue. Some companies provided barely adequate main caps and others went with the correct size or a bit more if the design would require a value between standard caps. There were design considerations to limit the size of the big caps like wear on the power switch that might have been part of the choice criteria. I will never be convinced that they put in the best capacitors for the musical performance of their amps. Some did, many did not and went with adequate.

But for selecting replacements today, it is known that some manufacturers build their large caps spec‘d at +/-20% at Minus 10% to save significant money on each production run. An engineer at Nichicon has said that is their build goal. With cap manufacturing more accurate today they can hit -10% easily and not get close to -20% so the cap is within spec. I’ve been hoping folks would post values of large caps they are installing and the N brand has been low, others maybe and still others were not.
 
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