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capacitor replacement...

ranatungawk

Aug 5, 2010
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if i replace a bad capacitor with a new cap with same capacitance and high voltage than the old one... can anything go wrong ?

ex: bad cap value is 10MFD & 10V.... i'm going to replace it with 10MFD 50V one.....
 

shrtrnd

Jan 15, 2010
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Normally no.
I'm assuming this is just an electrolytic in a power application.
Things get touchy in frequency sensitive circuits. Then the compostion and values of
the capacitors come into play. (Resistance/Capacitance timing).
Don't ever replace a bad cap with a lower voltage than the original.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Lots of things can go wrong, but very few of them would have to do with the capacitor, except one...

A higher voltage part is likely to be physically larger than that which it replaces. It may not fit, or it may push up against other components or the housing.

If the capacitor being replaced is a low ESR capacitor, or one with a higher temperature rating, or unpolarised, etc., you can also have problems.

Generally though, a higher voltage component will have lower ESR, and will run cooler (both due to this an its larger surface area) which will probably result in a longer, more reliable life for it.
 

Resqueline

Jul 31, 2009
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That usually presents no issues. Take note of the temperature rating though. If the 10V is a 105 degrees one and the 50V is an 85 degrees then replacement is questionable.
The only time I encountered a problem replacing a cap with a better one was in a computer monitor 20 years ago. It started to squeal with the lower ESR of the new cap.
Adding a series resistor of a couple of ohms fixed it..
 

ranatungawk

Aug 5, 2010
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Hi shrtrnd;

Thanks for the reply ! you have pointed out a very good point. this is not a power application but a frequency sensitive measuring equipment (8hZ TO 800hz; a capacitance meter; i have talked of this on this forum early!! ) i replaced all capacitors and all semiconductor items of this unit. but still it's idle value doesnt come to 0.00 , and show -0.3 0r -0.4.

if i put my hot soldering iron on a leg of a transistor or a capacitor, the meter idle reading come to 0.00 point. then after 2 hours the meter reading again goes to -0.3 or -0.4. when i replace CAPs i used 10MFD 50V ones for 10MFD 10V caps..... can this be a issue ?




Normally no.
I'm assuming this is just an electrolytic in a power application.
Things get touchy in frequency sensitive circuits. Then the compostion and values of
the capacitors come into play. (Resistance/Capacitance timing).
Don't ever replace a bad cap with a lower voltage than the original.
 

Resqueline

Jul 31, 2009
2,848
Joined
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Electrolytics are not used in places in measuring devices where they could have that kind of an influence. You'll have to look elsewhere for the answer to the zeroing issue.
Should we perhaps merge these two threads, being about the same thing? The wiring diagram for that cap meter is not easy to read or follow btw..
 

shrtrnd

Jan 15, 2010
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I remember your original post about the zero, now.
I also remember you saying something about when your meter zeroed, and when it didn't.
Are you sure when you're touching your soldering iron to the parts and have them zero that it's the heat? Consider the possibility it's the grounding. This is sounding more and more to me, like you've got a floating ground on your meter input. And the circuit is finding it's ground through your soldering iron (not the change in heat).
Brother, there has got to be a way to zero your meter easily, ....this is something simple you're not seeing.
Have you got capacitive trimmers in the probe inputs to the meter?
Are the grounds between probe inputs and meter connections free of corrosion, and making good contact?
Think something simple and basic, that you're just not considering.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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To see if it's heat or not, try it when your soldering iron is cold :)

Depending on what sort of soldering iron it is, you may have to do it just as you plug it in, but before it gets very hot.
 
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