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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 2nd Sep 2022, 3:10 pm   #1
Retrotechie
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Default Bi-polar electrolytic capacitors

Hi there, I’m working on a Sony pal decoder board from a professional piece of kit, and there are several surface mount bi-polar electrolytic capacitors used for signal coupling, which are in need of replacement (high ESR).

I’ve seen similar ones used in Panasonic Pro VHS models, and they are always a pain to source, especially surface mount types. In the past, I’ve used radials and sometimes the voltage rating has been quite a bit higher. CPC stock some of the values I need, but not all of them.

I’m curious if anyone has experience of fitted non electrolytic capacitors instead, such as mlcc ? Though this may be trickier for some of the higher values.

The values I’m looking for are:

10uf 16v
33uf 25v
47uf 6.3v
47uf 16v
100uf 6.3v

Thanks
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Old 2nd Sep 2022, 3:14 pm   #2
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Default Re: Bi-polar electrolytic capacitors

The dielectrics used in the very hich value ceramic capacitors have some nasty characteristics, not just large temperature coefficients. Microphony and non-linearity head the bill. They are also easily fractured in the larger physical surface mount packages both from board flexing and thermal shock from soldering/cooling. If you use them, look into the flexible-termination types for packages over 1206.

DAvid
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Old 3rd Sep 2022, 8:15 am   #3
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Default Re: Bi-polar electrolytic capacitors

Hifi Collective sells a decent range of bi-polar caps - https://www.hificollective.co.uk/sea...r%20capacitors bit pricey but.

Andy.
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Old 3rd Sep 2022, 1:36 pm   #4
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Default Re: Bi-polar electrolytic capacitors

Quote:
Originally Posted by Radio Wrangler View Post
The dielectrics used in the very hich value ceramic capacitors have some nasty characteristics, not just large temperature coefficients. Microphony and non-linearity head the bill. They are also easily fractured in the larger physical surface mount packages both from board flexing and thermal shock from soldering/cooling. If you use them, look into the flexible-termination types for packages over 1206.

DAvid
Thanks David, that’s good advice. I think it will be safer for me to stick to electrolytics.
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Old 3rd Sep 2022, 1:37 pm   #5
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Default Re: Bi-polar electrolytic capacitors

Quote:
Originally Posted by Diabolical Artificer View Post
Hifi Collective sells a decent range of bi-polar caps - https://www.hificollective.co.uk/sea...r%20capacitors bit pricey but.

Andy.
Thanks Andy, I will take a look at that site.
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Old 3rd Sep 2022, 1:56 pm   #6
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Default Re: Bi-polar electrolytic capacitors

Farnell seem to have plenty of non-polar (aka bi-polar) in radial through-hole types, https://uk.farnell.com/w/c/passive-c...st=non%20polar

Quite a lot of the surface-mount types are out of stock.

David
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Old 3rd Sep 2022, 2:12 pm   #7
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Default Re: Bi-polar electrolytic capacitors

If you have the physical space available and don't mind a bit of creative soldering origami, you can always put pairs of polar caps in series. If you consider this route, make sure to avail yourself to other points that give continuity with the SMD pads, i.e. nearby IC pins and the like, that you can anchor the caps to.
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Old 6th Sep 2022, 4:37 pm   #8
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Default Re: Bi-polar electrolytic capacitors

Unusual to see bI-polar smd electrolytics. Just had a look and Mouser seem to have all of them in stock.

Regards

Graham
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