capacitor value substitution in a PSU

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pucho812

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need to replace an 800uF electrolytic in a PSU that is consider vintage(from the late 70's).  The cap does not have screw terminals, and is axial with leads. This is the only one I have ever come across in such a manor.  Since the PSU is on the bench and not with at the moment, IIRC, it's either16V or 24V at max possible 50V. Can anyone suggest a sutable replacement? Would putting the next standard/usual value up of 1000uF be o.k.? I suspect yes but would like to hear peoples opinion.
 
thanks for that. yeah 1000uF is what I have been able to find that meets the space and type(axial). all I find in 800uF is screw terminal radial caps which will not work.

 
pucho812 said:
need to replace an 800uF electrolytic in a PSU that is consider vintage(from the late 70's).  The cap does not have screw terminals, and is axial with leads. This is the only one I have ever come across in such a manor.  Since the PSU is on the bench and not with at the moment, IIRC, it's either16V or 24V at max possible 50V. Can anyone suggest a sutable replacement? Would putting the next standard/usual value up of 1000uF be o.k.? I suspect yes but would like to hear peoples opinion.

1000uF is fine. I'll bet that the original 800 uF cap had a tolerance of +/-50%, anyway.

-a
 
Is there any other reason to replace a cap with the same type (axial vs. radial) apart from the fact that it fits better spacially? I've replaced plenty of axial caps with radial ones when I didn't have them at hand.
 
Here's what I've learned from people much smarter than me....
Those caps are for smoothing psu ripple. the ripple frequency is 60 Hz for half wave rectifier or 120Hz for full
wave.
The formula from The Art of Electronics is:
RC>1/f  (f = ripple frequency)

every doubling of cap value should drop ripple by half (hum down -6dB)
4x value = -12dB
8x value = -18dB
16x value = -24dB

 
living sounds said:
Is there any other reason to replace a cap with the same type (axial vs. radial) apart from the fact that it fits better spacially? I've replaced plenty of axial caps with radial ones when I didn't have them at hand.

exactly. I wouldn't care but space only allowed for axial in this case. To be honest it is specific  to that project.


dustbro said:
Here's what I've learned from people much smarter than me....
Those caps are for smoothing psu ripple. the ripple frequency is 60 Hz for half wave rectifier or 120Hz for full
wave.
The formula from The Art of Electronics is:
RC>1/f  (f = ripple frequency)

every doubling of cap value should drop ripple by half (hum down -6dB)
4x value = -12dB
8x value = -18dB
16x value = -24dB

thanks for the refresh of memory ;)
 

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