Author Topic: capacitor replacement  (Read 1495 times)

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Offline mensahotoo

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capacitor replacement
« on: April 19, 2017, 07:12:22 pm »
please I have an adapter and will like to replace the capacitor of 47uf and 400v with 68uf and 450v.
will it work?
 

Online Samogon

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Re: capacitor replacement
« Reply #1 on: April 19, 2017, 07:37:01 pm »
That will work, going up in parameters is safe.
 

Offline agehall

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Re: capacitor replacement
« Reply #2 on: April 19, 2017, 07:50:23 pm »
You don't say where the capacitor is being used. Going up in voltage is not a problem but changing the capacitance of it may or may not be OK. I'd recommend getting a 47uF cap instead of your 68uF one.
 

Offline rob77

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Re: capacitor replacement
« Reply #3 on: April 19, 2017, 07:56:30 pm »
if it's the main filter cap after bridge rectifier and there is no active PFC then it's safe to replace 47uF/400V with 68uF/450V. but i'm wondering if it fit's mechanically... 68/450 will be twice the volume of 47/400...
 

Offline donmr

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Re: capacitor replacement
« Reply #4 on: April 19, 2017, 08:05:09 pm »
if it's the main filter cap after bridge rectifier and there is no active PFC then it's safe to replace 47uF/400V with 68uF/450V. but i'm wondering if it fit's mechanically... 68/450 will be twice the volume of 47/400...

But a new 68/450 may still be smaller than an old 47/400.   I've had troubles getting new caps to fit into old devices because they are too small.
 

Offline james_s

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Re: capacitor replacement
« Reply #5 on: April 19, 2017, 08:09:36 pm »
I'm not going to make a blanket statement that it will always work, but in this case I think it is 99% likely that going from 47uF to 68uF will not cause any problems at all. If it physically fits I would try it, usually for things like this physical size is the limiting factor.
 

Online wraper

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Re: capacitor replacement
« Reply #6 on: April 19, 2017, 08:28:30 pm »
The only problem going up with capacitance is higher inrush current, therefore more stress on current limiting resistor and rectifier.
 

Offline rob77

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Re: capacitor replacement
« Reply #7 on: April 19, 2017, 08:48:59 pm »
The only problem going up with capacitance is higher inrush current, therefore more stress on current limiting resistor and rectifier.

yes agree that might be a problem for bigger PSUs in a case of significant capacitance change like 150uF to 470uF.
but in this case 47uF would suggest it's a small SMPS up to 50W approx. , so the rectifier is definitely safe , and the inrush limiting will be a NTC.
 

Online wraper

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Re: capacitor replacement
« Reply #8 on: April 19, 2017, 08:55:51 pm »
and the inrush limiting will be a NTC.
Very unlikely, in small power PSUs usually there is just a resistor, no NTC. Though this adapter might have PFC with a soft start.
 


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