Hello all,
I picked up a SSC cheap that needs some repair. DIP switches needed to be replaced and missing a cable. I noticed the disc capacitor at C13 was physically damaged and I’d like to replace it. The schematic shows it to be .01uf. Would anyone know what voltage these .01uf capacitors should be rated at?
You won't find ceramic disc capacitors with ratings under 50V, which is more than adequate for the application here. In other words, don't worry about it.
Edit: I can see from the schematic that C13 is across the +5 V rail and ground.
Thanks for the reply,
I wasn’t sure because I remember once I was told the ceramic disc on a Microsoft language card is 1kv. I was blind on this application and thought it better to ask than to guess. I’m sure 50v are plenty available as I’ve used 50v on other projects before. I can’t get a good clear pic of this one but it looks like a mouse chewed all the ceramic off around the edge and the bare metal is exposed.
Thanks for your help.
Randy
Just looking at a few other ceramics on the board, 330s in particular, they have 1kv printed right on them. Nothing on the .01s. And 1kv .01uf are pretty common on eBay but I found 50v.
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Ceramic capacitors are so-called because they use a ceramic material as a dielectric. There are several different kinds of ceramic dielectrics, with widely varying dielectric constants (represented by the symbol epsilon). As the dielectric constant increases, the parameters of the capacitor become less stable. This is important because low-stability capacitors can change value over time or when power is applied to them, which might not work in the circuit.
I don't know which parts you are looking at, but it wouldn't be uncommon for the 1KV parts to be Z5U and the 50V parts to be C0G. As the dielectric constant increases, the space taken by the capacitor becomes smaller due to higher CV per volume effects. So it's possible to have a high-voltage withstanding capacitor which would normally require a larger space, squeezed into a smaller space.
50V components should work fine in this application, but clearly the 1KV parts also worked as those were originally used. You can use whatever is most convenient.
I was able to get a good pic of it after I removed it. I tested it on a component tester and it kept coming up as a resistor. Which I'm not overly suprised.
IMG_2718.PNG
You can see the lower text is "Z5U", which is the EIA designation for a less stable high-K dielectric.
This can normally be substituted with X5R which has a wider operating temperature range and tighter tolerance values. 50V is enough. I would spend a few minutes matching the dimensions and lead spacing, though, since that will be what determines if the replacement visually fits.
The ones I got just say 103K. And “HS” below it. The M I believe is +/-20%. The K should be a tighter tolerance, no? The ceramics I ordered are physically identical to the chewed up one so lead spacing won’t be a problem.
The capacitor arrived today and I installed it. Wrote an image with ADTpro, no issues. Thanks for your help and schooling me on those markings. I read a little about the Z5U caps and it said that they were used as a general capacitor with normal operating temperatures and small size and low budget were factors. Glad I was able to repair the card with as little effort that it needed.