| Electronics > Projects, Designs, and Technical Stuff |
| Replacing circular ceramic capacitors with??? |
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| TERRA Operative:
I'm looking to replace some old circular ceramic capacitors on a bit of test equipment. The caps are on the BNC jacks, between the isolated shield and chassis as seen in the attached images (You can see one is chipped, hence the replacement) Now, I can find piles of 50V circular ceramic caps in Akihabara, but not much else... My question is, can I just use something like this? https://www.digikey.com/product-detail/en/tdk-corporation/FA26C0G2A223JNU06/445-180656-1-ND/ If not, what would the best substitute capacitor type be? I don't think this is overly critical (Hence the use of circular ceramics) but I just don't want to be way off the mark... |
| drussell:
Why are you replacing them? Ceramic capacitors tend to be stable within their original specifications and are very reliable. edit: Sorry, missed your comment about one being chipped. I'm sure it still works fine and you could just touch a dab of epoxy over the chipped area to seal and protect it, though obviously you could just replace them I suppose. For cost and size reduction most ceramic capacitors are now a multilayer design rather than a single disc, except for ones that are rated at higher voltages where the physical ceramic layer needs to be thicker so it is more practical to make the traditional disc style. You can still find lower voltage versions, though, just less commonly. For example, Vishay D Series or S Series (datasheet), eg. D203Z59Z5UL63L0R or S223M75Z5UN83J0R at Digikey. |
| bson:
You should be able to use any ceramic cap with > 100V rating and reasonable capacitance. (22nF?) These just decouple noise; no one in their right mind would use Y5V caps for their signal properties. Disk or not doesn't matter. |
| coppercone2:
Is the pulse load rating of those disks different then modern components? If they are used in the traditional manner, directly after a wire run, can you actually replace them with a component that has similar or better durability in a different form? What comes to my mind is surface area. I mean their decay-vs-overload compared to smaller parts. I would imagine they dissipate heat better and have a larger area so the field density is lower. Also, how is the overload/transient durability of different dielectric grades (i.e. z series vs the supposedly traditionally higher end X series)? |
| TERRA Operative:
Cool, looks like the ones I selected would work, although a bit overkill, the ones drussel found seem closer to the original specs/shape (with higher rated voltage). I'm not sure pule load rating is too much of an issue for these caps? They are just used for coupling the shields of the test leads to the equipment chassis. How would I determine what that value is for the original parts if it is a critical variable? |
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