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To the best of my abilities, I'm trying to repair an Atari 800XL which was sold as "non working unit". I found a new graphics chip and it's working ok. I though that, since I had it opened up, it wouldn't be a bad idea to replace the caps, even though they didn't show any leakage. So I did, i changed all of them but 3 are still remaining. They do not have any polarity marking and I eventually learn that they are Non-Polarized Electrolytic Capacitor. The marking reads:

"Nicon 4.7 uF, 35v, NP, -40 to +85ºC"

I'm trying to find replacement for these but I can't seem to find exactly the same and, since my knowledge on the topic is very limited (no formal education in electronics whatsoever) I would need some help.

The closest thing I found are capacitors with the same range of values but marked as "Bi-Polar" instead of "NP". I don't really know if it means the same as info I found in internet is contradictory.

If anything else fail, could I replace these capacitors with non-electrolytic ones? Again, since my lack of knowledge of non of them have polarity... all seems the same through my eyes...

Any help will be appreciated.

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  • \$\begingroup\$ non polarized or bipolar are the same. \$\endgroup\$
    – Marko Buršič
    Oct 15, 2018 at 11:13
  • \$\begingroup\$ Knowing nothing else about them, it's probably best to use electrolytic capacitors to replace them. The circuit may rely on the comparatively high ESR of electrolytic caps, or some other quirk of the particular capacitors in question. When you don't know for a fact that you can use a different type, you should generally replace parts with as close to the original as you can. \$\endgroup\$
    – Hearth
    Oct 15, 2018 at 12:05
  • \$\begingroup\$ See here, Can you make a non-polar electrolytic capacitor out of two regular electrolytic capacitors?, and here, Can two electrolytic capacitors be made into a bipolar? \$\endgroup\$
    – Antonio
    Oct 15, 2018 at 15:24
  • \$\begingroup\$ Thank to you all. @MarkoBuršič if you could add your comment as an answer, I would mark it as solved. \$\endgroup\$
    – Marcal
    Oct 16, 2018 at 9:39

2 Answers 2

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Several solutions
1) put two back to back series capacitors of 10uF/35V (negative with negative)
2) one polyester 4.7uF 40V like red WIMA (have similar small size)
3) buy a bipolar or NON polar electrolytic capacitor from a catalog distributor or better audio components or ebay. They are still selling them.

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You can buy Nichicon UVP1J4R7MED1TA 4.7uF/63V bipolar/non-polar caps from distribution at a reasonable price.

You may not want to bother replacing them if the product is still working.

Some manufacturers distinguished between NP and BP, with one of the two (BP) intended only for occasional polarity reversals.

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