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RIFA replacement advice
Posted by: blindowl on 2023-01-04 04:29:20
I want to replace the RIFA capacitors in a Macintosh IIci power supply but I’m having troubles finding components with the exact specs from my local electronics dealer.
  • Is it okay to use caps rated for 275 V instead of 250 V? I know it’s normally okay to use capacitors rated for higher voltages, but as this is mains voltage I just want to make sure that the same applies to these?
  • I can't find any 3300 pF Y (C6) film capacitor. Is it okay to use a ceramic filter capacitor with the same values instead? Specs here: https://www.electrokit.com/uploads/productfile/41010/otHV-Ceramic-Cap_dat_e.pdf
RIFA capacitors on this specific PSU (Astec AA15830):

C2: 0,1 uF X2 250V
CA: 0,047 uF X2 250V
C4: 4700 pF Y 250V
C5: 4700 pF Y 250V
C6: 3300 pF Y 250V
Posted by: cruff on 2023-01-04 11:30:43
Yes it is okay to use a higher voltage rating replacement.

If the replacement for the Y type caps are also Y type caps then you can use a different type. If the ceramic capacitor is not Y rated then you can not use it as a replacement. Since you didn't specify the manufacturer's capacitor series in the PDF you linked I can't say for sure if this is the case or not.
Posted by: blindowl on 2023-01-04 11:46:14
Thanks for your help! The ceramic cap is this one: https://www.electrokit.com/produkt/x1-y1-3-3nf-250v-10mm/

It says “X1/Y1”, so should be alright then?
Posted by: cruff on 2023-01-05 20:01:51
Yes, that appears suitable. Here is a link to a good description of what the X and Y capacitor classes mean. https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/
Posted by: blindowl on 2023-01-06 02:52:17
Yes, that appears suitable. Here is a link to a good description of what the X and Y capacitor classes mean. https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/
Thanks!
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