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Old 03-26-2023, 04:12 PM   #1
Amminadabz
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Question What to replace an unobtainable bipolar elctrolytic?

Howdy folks, its been a minute.

I'm working on a capacitor kit for my Korg C-15 digital piano, and it has a couple bipolar electrolytics (C27 and C34) on the analog board for which I can only find one direct replacement, but it's sold in multiples of 50.

I've got a couple work-arounds in mind (Ebay NOS, testing with the og part, swapping for a ceramic), but what part can I recommend that will be reliably obtainable in the future? Would a ceramic or MLCC (not entirely sure what the practical difference is) be a good general replacement for bipolar electrolytics? It's hard to find succinct information about this.
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Old 03-26-2023, 04:37 PM   #2
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Default Re: What to replace an unobtainable bipolar elctrolytic?

film so long as its not too large .
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Old 03-26-2023, 04:56 PM   #3
lti
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Default Re: What to replace an unobtainable bipolar elctrolytic?

I would also suggest film caps for an audio circuit like that. The schematic I found shows that they're just coupling caps on the amp input. Kemet R82 and TDK B32529 series seem readily available and small enough that they should fit.
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Old 04-23-2023, 11:37 PM   #4
bestsystem
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Default Re: What to replace an unobtainable bipolar elctrolytic?

get nichicon muse BP , 1.0uf, 2.2 or even 4.7uf won't go wrong for coupling.

According to audio circuit books by Douglas Self, reasonably oversized coupling electrolytic caps give less distortion.
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Old 04-24-2023, 10:03 PM   #5
lti
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Default Re: What to replace an unobtainable bipolar elctrolytic?

Nichicon discontinued all of their smaller caps. Those bipolar audio caps were my first thought as well.

I did see a Rubycon NW7 series cap in stock on Mouser, so that's an option if you don't want to switch to film caps. It will be smaller than the original.

If you increase capacitance, there are a lot more bipolar electrolytic options.
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Old 04-25-2023, 09:46 PM   #6
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Default Re: What to replace an unobtainable bipolar elctrolytic?

Quote:
Originally Posted by lti View Post
Nichicon discontinued all of their smaller caps. Those bipolar audio caps were my first thought as well.

I did see a Rubycon NW7 series cap in stock on Mouser, so that's an option if you don't want to switch to film caps. It will be smaller than the original.

If you increase capacitance, there are a lot more bipolar electrolytic options.
it should be ok to increase to a few uF without major issue, if a design is critical to excess coupling cap capacitance or inrush charge up time constant, then film cap would have been chosen instead.


I have a build mic peramp that got a 220uf coupling cap between 2nd~3rd opamp stages, 5k ohm resistor to ground in 3rd stage, takes me 2 senconds to settle when powering on before recording, all are fine.
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