cap question

demogo

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Installing a Bob Roberts 288 pentranic cap kit right now and got near the bottom and noticed that Bob has me replacing a 470uf 35v cap with a 470uf 25v cap from his kit.

That can't be right, can it?
 
It's probably alright. If he put it in there, he probably looked over the schematics and figured out that 25v would be alright.

Sometimes the manufacturers put something at a different voltage because they were able to buy the caps in bulk and it's easier for them to just throw a 35v in there.

Also, finally you're probably alright anyways since there's not much difference between a 25v or 35v. It may fail faster, though if it indeed is underrated.
 
Ugh.

Found a local place that carries it but it's about 25-30 min away...

I only want to do this once -- I think I'll be conservative and go get a new one.

Looks like his cap kit is missing another cap too... grrr.
 
Installing a Bob Roberts 288 pentranic cap kit right now and got near the bottom and noticed that Bob has me replacing a 470uf 35v cap with a 470uf 25v cap from his kit.

That can't be right, can it?

This one?

http://arcarc.xmission.com/PDF_Monitors/Pentranic CH-288 Switchable.pdf

Whenever you have a doubt, always try to find the schematic to see what they have listed. Someone before you might have replaced it with a higher voltage cap because that's all they had on hand, but Bob's will work because it's what was originally called for.

Or Bob made his list from a different schematic.

Often when I rebuild chassis', if I need a 100u16v and don't have one, I'll throw on a 100u25v instead if I have one. Now, then next guy who has it (if it's not me) may buy a kit from Bob (instead of using bulk caps like me) and wonder why Bob included a 100u16v for that spot...
 
Yeah, Bob told me that the one he included was over spec as it was. So apparently the 35v variety was way overkill.

It may have come that way from the manufacturer or it may have been someone else's cap from a previous capkit.

BTW, not knowing how to read schematics, where does it tell you what size each cap is?
 
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BTW, not knowing how to read schematics, where does it tell you what size each cap is?

Some schematics will come with parts listings, but if you only have a schematic:

You zoom in, scroll around until you find the cap you're trying to replace, then check the value. In the pic below, C326 is a 1000uf 35v cap...

SchemCapHelp.jpg
 
Got it -- thanks!

It seems like not all of the caps have values associated with them -- or some of the C's aren't caps perhaps.

But I did find C970 and it indeed is called out as a 470uf 25v part.

You learn something new every day. :)
 
Got it -- thanks!

It seems like not all of the caps have values associated with them -- or some of the C's aren't caps perhaps.

If you are referring to something like C394 in the pic above - where it says "104" - yes, that is a capacitor, but of a different type (most likely a ceramic cap). Those caps use codes to infer their value in picofarads, with the first two numbers part of the value, and the last number showing how many zeroes to put on the end (in this case 4). That would give you a value of 100000pf, or 100nf, or 0.1uf.

Or you can just type the code into this:

http://www.electronics2000.co.uk/calc/capacitor-code-calculator.php
 
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Wow, great info, thanks!
 
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