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The most shot-put components - a few words about noise filters and RIFA capacitors

filipcichowskidev 2121 41

TL;DR

  • Polish measurement equipment often uses Silesia mains filters and notorious RIFA paper capacitors that fail after decades.
  • The filter topology uses an input choke for common-mode noise, two Y capacitors to earth, and an X capacitor across L and N for differential noise.
  • In HP digital oscilloscopes from the 1990s, these capacitors were built into filters integrated into the socket and switch.
  • Cracked resin lets moisture in, the capacitors leak, and the filter can explode, swell, or spray tar inside the unit.
  • Repairs usually mean replacing them with film or polypropylene capacitors such as WIMA or Wurth Electronics, or removing the filter entirely.
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  • #31 21781367
    filipcichowskidev
    Level 10  
    Posts: 53
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    Rate: 86
    >>21781353

    With TN-C you don't give a differential because there is no way. I was referring to a working TN-S installation - indeed I should have written that.
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  • #32 21781414
    Wawrzyniec
    Level 38  
    Posts: 3975
    Help: 390
    Rate: 1065
    You think about TNS, write about TNC and claim that there is no ppor protection in TNC. Interesting.
  • #33 21781420
    filipcichowskidev
    Level 10  
    Posts: 53
    Help: 3
    Rate: 86
    I'm letting go of any further discussion because it goes in the direction of writing for the sake of writing and not getting anywhere together.
    You are interrogating me here as if I were a police officer and you think what? That I'm going to explain every mistake, everything? Someone has got something wrong here! It's a waste of energy. You have to set firm limits.
  • #34 21781476
    robig
    Level 23  
    Posts: 458
    Help: 59
    Rate: 139
    filipcichowskidev wrote:
    Hard boundaries need to be set.

    You are right, it does need to. You describe your grievances and wishes in the technical forum, your posts are not substantively correct, more experienced forum members write and suggest to you how it is and how it should be, you argue with them considering your often erroneous "view of me" as more "yours", and finally, with a nod, you shoot a furor, in the Elektroda forum. Echhh, no one is your enemy here, it's just that you unfortunately can't take constructive criticism.
    Keep warm and less nerve on a daily basis
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  • #35 21781804
    Olkus
    Level 32  
    Posts: 3916
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    Rate: 914
    It's worth knowing that it's the capacitors that can mess around.
    It's interesting that you can still buy these, so can Wima MP3s (I almost ordered one recently) sometimes the prices reach absurd, which is a bit strange.

    Regards,
    A.
  • #36 21782004
    Wawrzyniec
    Level 38  
    Posts: 3975
    Help: 390
    Rate: 1065
    filipcichowskidev wrote:
    That I am going to explain myself from every mistake, from everything? Someone has got something wrong here!

    T no confusion. Your knowledge .
  • #37 21782029
    Adam Pyka
    Level 19  
    Posts: 469
    Help: 18
    Rate: 20
    filipcichowskidev wrote:
    I will forego any further discussion, because it goes in the direction of writing for the sake of writing and not reaching a common goal.

    For my part, I would like to thank you very much for raising this topic, it was worthwhile to remind myself and to put my knowledge in order.

    However, I do not like the current attack on the author - the forum is there to raise topics, also to "talk" and not just "make a lecture". With this approach, the forum will quickly die because no one will post anything new, fearing confrontation and simply - hejt. Not everyone has to be an expert!
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  • #38 21782113
    398216 Usunięty
    Level 43  
    Posts: 34034
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    I may be wrong, but if I may, I will state my opinion.
    The topic originally set up by the author (because he later changed the content of the first post) was precisely in the form of a "lecture" and not a keynote. The author even (at least that is how I perceived the tone of the statement) reprimanded manufacturers for using perishable components (even though the thread was about a device that was already several years old), which triggered a discussion about the lack of physical possibility for a manufacturer of components to assess their durability at the time of production. Then a dispute arose arising from the Author's misunderstanding of the idea of an installation with zero protection, the dispute contributed to a further exposure of the Author's ignorance on a subject on which he wanted to have the final say all the time. And this (let me remind you - this is only my opinion) was not in harmony with the forum as such. The forum has certain guidelines and rules - and they are detailed in the Forum Rules, and unfortunately, the level of knowledge presented by the Author was not compatible with tolerating such a tone of speech. Yes - the issue raised in the topic is interesting, but the way it was presented and further development of the topic by the Author is not necessarily so.
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  • #39 21782179
    gulson
    System Administrator  
    Posts: 29250
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    Informatively, I moved this from the Beginners section to Articles, finding it an interesting topic for discussion.
  • #40 21782772
    terminus
    Level 21  
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    I get the impression that no one has understood the idea of the topic of this thread.
  • #41 21783550
    kombo
    Level 14  
    Posts: 56
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    Rate: 39
    One faulty capacitor and so much damage done :D (note that this is just my opinion).
  • #42 21888732
    Olkus
    Level 32  
    Posts: 3916
    Help: 132
    Rate: 914
    I've just hit a cracked Rify, this time it's Y-grade switched between L and N and PE. It's a good thing the article came up because I probably wouldn't have noticed it straight away, they will be replaced with ceramic.

    The most shot-put components - a few words about noise filters and RIFA capacitors

    Regards,
    A.
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FAQ

TL;DR: Old Silesia/RIFA-style EMI filters use 2 Y capacitors to earth and are known to crack; “replace if found, always!” applies. [Elektroda, filipcichowskidev, post #21775596]

Why it matters: This FAQ helps bench technicians and restorers spot failing mains filters and choose safe, modern replacements, reducing shock risk and downtime.

Quick Facts

What exactly fails in old Silesia/RIFA mains filters?

Paper-dielectric X and Y capacitors absorb moisture after the resin case cracks. Leakage rises, leading to smoke, bangs, or tar ejection. The common‑mode choke usually survives. The EEVBlog rule of thumb quoted is “replace if found, always!” because these parts age poorly. [Elektroda, filipcichowskidev, post #21775596]

How much leakage current is acceptable during safety testing?

Use 0.75 mA under normal conditions per EN 50699 as a practical acceptance figure in PAT workflows. If you read values near or above this, investigate immediately. “Safety limits exist for a reason.” Replace suspect X/Y caps before returning the device to service. [Elektroda, filipcichowskidev, post #21778064]

I measured 10 mA from L to PE. What should I do first?

Isolate mains, discharge capacitors, and inspect X/Y caps for cracks or discoloration. Replace degraded paper capacitors with modern polypropylene film parts, then retest insulation/leakage. A real case showed 10 mA L–PE; replacing cracked RIFAs with Würth restored compliance the same day. [Elektroda, filipcichowskidev, post #21775678]

What are X and Y capacitors in EMI filters?

X capacitors connect across L–N to suppress differential‑mode noise. Y capacitors connect from L and N to PE to shunt common‑mode noise. Old paper types drift and leak; modern polypropylene X2/Y2 parts are safer and more reliable. [Elektroda, filipcichowskidev, post #21775596]

Why do these filters fail after years of service?

They operate hot and across the mains from power‑on to power‑off. Aging, voltage spikes, and poor historical materials accelerate dielectric breakdown. As one expert notes, components can fail “by themselves” after decades; this is a known lifecycle outcome. [Elektroda, 398216 Usunięty, post #21778433]

Are WIMA MP3 X2 or other brands immune to this problem?

No brand is immune to misuse or aging. Users reported a WIMA MP3 X2 that blazed and contaminated the supply. Select suitable class‑rated film parts, observe temperature and surge ratings, and locate them away from heat sources. [Elektroda, tos18, post #21778451]

Can modern equipment still show RIFA branding?

Yes. RIFA AB ended capacitor production in 1988; the brand moved through Evox Rifa and later KEMET (2007). You may still see RIFA‑marked stock or labeling even when supplied under KEMET. [Elektroda, gregor124, post #21779893]

Does older gear have to meet today’s safety standards?

Legally, equipment must meet the standards that applied at market entry. Current requirements do not retroactively bind earlier devices. Your workplace can impose stricter internal policies for continued use, though. [Elektroda, ArturAVS, post #21775715]

What’s the difference between common‑mode and differential‑mode noise?

Common‑mode noise appears on L and N simultaneously relative to PE; the choke and Y caps shunt it to earth. Differential‑mode noise exists between L and N; the X cap suppresses it across the line. [Elektroda, filipcichowskidev, post #21775596]

How do I retrofit a failed Silesia can filter with discrete parts?

  1. Remove the potted can and clean tar residue with extraction petrol or WD‑40. 2. Recreate the topology: common‑mode choke, two Y caps to PE, one X across L–N, all class‑rated film types. 3. Verify wiring, then run insulation and leakage tests before power‑up. [Elektroda, filipcichowskidev, post #21775596]

Are RCDs appropriate in TN‑C installations for these issues?

No. In TN‑C, protective earth and neutral are combined; RCDs are not applied. Use RCDs in TN‑S. A poster clarified their earlier mistake, noting RCDs fit TN‑S, not TN‑C. [Elektroda, filipcichowskidev, post #21781367]

I can’t source a 1990s IEC inlet filter from HP—what now?

Those combined switch‑socket filters can be hard to obtain. Consider bypassing the failed module and recreating the filter with discrete class‑rated film X/Y caps and a choke, observing creepage and wiring discipline. [Elektroda, filipcichowskidev, post #21775596]

Were RIFA capacitors common in Revox equipment?

Yes. Users report RIFA parts widely used in Revox gear, with some still not replacing them during service. Proactive replacement reduces future failures. [Elektroda, koko0, post #21779811]

What pre‑power checks should I perform on vintage mains gear?

Use an insulation tester before any live work, wear insulating gloves and goggles, and inspect transformer leads and sleeving. Replace degraded mains parts first, then power through an isolation transformer or variac. “A little paranoia never hurts.” [Elektroda, filipcichowskidev, post #21781219]

How do I clean up after a capacitor ‘tar bomb’ inside equipment?

Mechanically remove chunks, then dissolve residue using extraction petrol or WD‑40. Protect coils and delicate parts from solvents, and re‑varnish if needed. Finish by replacing the failed capacitors with polypropylene film types. [Elektroda, filipcichowskidev, post #21775596]
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