Nichicon Electrolytic Capacitors leaking - common problem? ( Rifa X and Y also)

[Jay_Diddy_B]

Hi group,

There are some components that are changed on sight, in order to extend the life of equipment.

Rifa EMC capacitors

I have seen these, where for some reason, where the outer case is cracked. These tend to fail is a spectacular manner.

Schaffner EMC Filters

This may be an extension of the Rifa capacitor issue, Rifa capacitors were once regarded as the premium EMC capacitors for X and Y applications.

I am concerned about older Nichicon capacitors, or more generally electrolytic capacitors with phenolic bases. I have repaired a Keithley 2001 that was almost wrecked by leaking electrolytic capacitors.



Link: https://www.eevblog.com/forum/testgear/restoration-glory-of-keithley-2001-dmm/msg698411/#msg698411

HP 6035A



Link: https://www.eevblog.com/forum/testgear/hp6035a-500v-5a-1kw-power-supply-repair/msg698176/#msg698176

HP 6671A

 

Thread: https://www.eevblog.com/forum/testgear/hp-6671a-option-j05-j09-5v-250a-power-supply/msg3252034/#msg3252034

The first unit in this thread is mine. Forum member Shef  reported a very similar problem.

I was working on another 6671A this weekend, the capacitor had just started to leak but there was no damaged to the board after cleaning.

Preventative Maintenance

I had another HP 6671A apart to replace the Rifa and Nichicon capacitors. In this unit I pulled the Nichicon capacitors. I found that the seal was the more recent plastic seal and there was no evidence of leakage at all:




This shows the old style and new style of base. These are the same series and same value.

Does anybody know when Nichicon switched to the new style of construction?

Do you have to be concerned about these new ones leaking as much as the older ones?

My experience is limited to Nichicon, because I have found these in the equipment that I have repaired. Are other brands just as bad?


Regards,
Jay_Diddy_B

[Smoky]

I think the PR series is discontinued and its replacement is the PS series. If the PW series will fit, use them because they have a higher ripple current capacity. They're all categorized as switching power supply capacitors. Btw, if you see a PF series, yank 'em, they're "leakers" big-time!

[tautech]

Dunno any radial caps that don't use a rubber seal now, even the most horrible cheapest rubbish.

Certainly anything of value that uses caps with phenolic bases should have them changed out ASAP as they will already be long past their 'best before' date.

[Shock]

There were a few defective series (early failures) from Nichicon and United Chemicon. It happened to be around the time of the capacitor plaque early to mid 2000s.

The Rifas are more an end of life problem (as far as I can tell) and likely age or application. Similar to the older tantalum capacitors they fail spectacularly so are more noticeable. There is the Chinese stuff which is crap quality and affects whole brands, so roll the dice on that one.

Then you have physical leakage due to age which will be around the 1990s and older now, either that or they dry up.

[wraper]

I think the PR series is discontinued and its replacement is the PS series. If the PW series will fit, use them because they have a higher ripple current capacity. They're all categorized as switching power supply capacitors. Btw, if you see a PF series, yank 'em, they're "leakers" big-time!

PR should be some very old general purpose series, when thing like LOW ESR capacitors did not even exist yet. Yet you suggest that LOW ESR series should be a replacement for it.

[wraper]

There were a few defective series (early failures) from Nichicon and United Chemicon. It happened to be around the time of the capacitor plaque early to mid 2000s.

Issues were only with LOW ESR series, HM and HN for Nichicon in particular. These are way older and certainly not LOW ESR.

[floobydust]

I would do an autopsy, take one apart and see how the bung is. There's many factors at play.

I find old electrolytics with the phenolic disk use natural rubber which dries out, shrinks and cracks. Synthetic rubbers are superior EPDM or EPT (Ethylene-Propylene Terpolymer) but still can fail.
The long duration, hot wave soldering of this board could also contribute to short capacitor life. I see trapped flux as well which can attack the rubber.

I remember a period (early 80's?) where most electrolytics this size had the same construction- using phenolic. Then I believe it was replaced with the synthetic rubber bung and slot cutouts for wash, for most manufacturers.

[Smoky]

I think the PR series is discontinued and its replacement is the PS series. If the PW series will fit, use them because they have a higher ripple current capacity. They're all categorized as switching power supply capacitors. Btw, if you see a PF series, yank 'em, they're "leakers" big-time!

PR should be some very old general purpose series, when thing like LOW ESR capacitors did not even exist yet. Yet you suggest that LOW ESR series should be a replacement for it.

Well, maybe you should read the Nichicon catalog yourself?

[james_s]

I had some of those Nichicon caps leak in TDS400 series scopes. They were around 30 years old though so I'm not sure I can really fault them for it. I've had one of those RIFA capacitors burn up once too but again it was over 30 years old so I don't really buy into the "RIFA caps are crap" thing, they just have a finite life like many other parts. The one Schaffner filter I opened up didn't have RIFA caps in it, it had more modern looking blue ones with an epoxy fill. Nichicon capacitors are top notch and they're one of my go-to brands, I'm not sure I'd expect them to last 30 years in a SMPS or other high ripple application though.

[2N3055]

I would do an autopsy, take one apart and see how the bung is. There's many factors at play.

I find old electrolytics with the phenolic disk use natural rubber which dries out, shrinks and cracks. Synthetic rubbers are superior EPDM or EPT (Ethylene-Propylene Terpolymer) but still can fail.
The long duration, hot wave soldering of this board could also contribute to short capacitor life. I see trapped flux as well which can attack the rubber.

I remember a period (early 80's?) where most electrolytics this size had the same construction- using phenolic. Then I believe it was replaced with the synthetic rubber bung and slot cutouts for wash, for most manufacturers.

This.

I've seen elkos with phenolic disk leak (it was popular design of the era), not related to Nichicon. Most of those that leaked were in very old equipment that had hard life..
So I would say wear and tear....

[precaud]

I recently rebuilt two DACs, same model. Going by the serial numbers and component date codes, they were made about 6 months apart - late 1999 to early 2000. Both had ten 100uF 16V Nichicon lytics of the new-style construction. In the earlier unit, all ten had leaked and made quite a mess. In the later unit, they were all fine.

[Jay_Diddy_B]

Hi group,

Here are some pictures from one of the phenolic-based electrolytic capacitors. It is a Nichicon PR(M) 1000uF 50V pulled from a power supply with serial starting 3215A. I estimate this to be 1992 production.

Teardown



I have torn away the aluminum case to reveal how the can to base is sealed.




This is with the core removed from the aluminum case.




I suspect the seal that failed is around one or both pins. The out seal is well crimped during the construction.




This is the inside of the rubber seal.




This is the outside of the base. I tried to separate the phenolic from the rubber and I was unable to.

Regards,
Jay_Diddy_B

[Jay_Diddy_B]

Hi groups,

The second HP 6671A that I removed the capacitors from was branded HP or the front Agilent on the serial number label.

Agilent started doing business on November 1st 1999.

The serial number starts MY 4100 so that is 2001.

This had the new style capacitors.

I am going to change the capacitor anyway since I have the unit apart.

Have members seen the new style capacitor leak?

Could it be that this problem was fixed in or around 2000?

Regards,
Jay_Diddy_B

[Jay_Diddy_B]

Snip ...

 I've had one of those RIFA capacitors burn up once too but again it was over 30 years old so I don't really buy into the "RIFA caps are crap" thing, they just have a finite life like many other parts. The one Schaffner filter I opened up didn't have RIFA caps in it, it had more modern looking blue ones with an epoxy fill.

Snip ...

I am not sure that I buy the argument that the Rifa capacitors are crap either. At the time the Rifa capacitors were very widely used and regarded as the 'gold standard' in in EMC capacitors.

I think that some of the reputation comes from the position in the circuit. They are connected either from line to neutral or from line (or neutral) to ground. They are exposed to large transients and high fault currents.

Unless I see some evidence of distress, like a cracked case, I am tempted to leave them alone.

Comments?

Regards,
Jay_Diddy_B

[wraper]

I am not sure that I buy the argument that the Rifa capacitors are crap either. At the time the Rifa capacitors were very widely used and regarded as the 'gold standard' in in EMC capacitors.

I think that some of the reputation comes from the position in the circuit. They are connected either from line to neutral or from line (or neutral) to ground. They are exposed to large transients and high fault currents.

They are crap and they crack even when NOS caps are just sitting in a box. No other capacitor is known to crack and explode in flames in such application. They may lose most of capacitance due to shorting and self healing but none of them explodes except Rifa.

[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]

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

It's shell that cracks.

[amyk]

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?

Just be careful not to poke too close to the bungholes, lest you create a leak...

[syau]

All the RIFA or line filter gave out magic smoke when wife watch me playing the “toys” 

Yes, I know that there is high possibility for those RIFA giving up when plug into 220V supply after sitting most of their life in 115V environment, but the timing can’t be so coincident. 

Worst case is those capacitor slowly leaking through earth which trip the GFI after some time.

Note: Not sure why HP 8950L series SA power supply use X instead of Y

[Refrigerator]

RIFA caps failing wouldn't be that big of an issue if they didn't fail in the exactly opposite way a class X or Y capacitors are designed to fail.

[wraper]

Note: Not sure why HP 8950L series SA power supply use X instead of Y

Are you sure it's X? This crap comes in both X and Y flavor. https://content.kemet.com/datasheets/KEM_F3016_PME271Y_Y2_250.pdf

[syau]

You are right, it was marked as 250-Y2, 300-X1. It measured 3x MOhm when I applied 250 V across it. The good one measure few hundred MOhm.