Electronics > Repair
Nichicon Electrolytic Capacitors leaking - common problem? ( Rifa X and Y also)
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Jay_Diddy_B:
Hi,

I found this Rifa date code table here:

https://www.yumpu.com/en/document/read/9082394/rifa-evox-y-2-emi-suppression-capacitor-1mf-west-florida-




And I looked at the date code on the Rifa capacitors in my HP 6671A. These capacitors are marked 'M7':




This date code July 2000 is consistent with the date from the serial number of the unit 2001.

I am not sure how to read the date code 'CS1' on the picture shown by wraper.

Regards,
Jay_Diddy_B
floobydust:
Is the bung still soft and pliable? I use a non-pointy (pen end) to press and see. The leads seem to poke through a sleeve in the bung?
In your one pic the top is domed so I would think the cap overpressured and then took the piss?
I have seen big value Panasonic FC leaking at the leads, so that must be the weak spot.

The Rifa capacitors are unique having a paper dielectric and the clear epoxy. I found a box of new old stock in the lab and the sides were cracked on many of them where the epoxy is thin. I think they aren't dimensionally stable - my theory: the epoxy shrinks with age and crushes the capacitor. Other people say it's a moisture ingress problem once the housing cracks.
I'd emailed Vishay and said WTF are you doing still selling these PME271's, they should be recalled. Schaffner should recall their line filters using them too.
Can't see the demand for a paper vs plastic capacitor. Paper is still king in the utility industry for an insulator in transformers although oil-immersed.
Jay_Diddy_B:
Hi,

There used to be, (still is?) a construction of capacitor called 'mixed dielectric'. It was a combination of oil impregnated paper and plastic. It was very robust and very reliable.

The oil filled the voids in the capacitor to eliminate corona discharge. The paper was there to keep the oil in place. The plastic film can withstand very high dc voltages.

I have ordered PHE850 and PHE840 series capacitors as replacements. They are reasonably priced at Digikey.

Jay_Diddy_B

james_s:
I winder how many of the opaque capacitors have cracked epoxy that you just can't see?
wraper:

--- Quote from: james_s on September 28, 2020, 08:14:52 pm ---I winder how many of the opaque capacitors have cracked epoxy that you just can't see?

--- End quote ---
It's shell that cracks.
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