Dear Viewers,
I am talking about an important topic in relation to Electronic ballasts manufactured by Tridonic in the 1990s and 2000s.

While I was taking apart a Tridonic ballast from around this era I unfortunately noticed that it contained a RIFA PME series capacitor which unfortunately do not have the best reputation at all. Those who constantly work on old Electronics from around the 80s and 90s would especially know this. The RIFA in the ballast I took apart was completely cracked.

This is a Tridonic PC 1x38-35 DD COMBO ballast from 2006.

RIFA capacitors are notorious for cracking very quickly and eventually fizzling potentially causing a fire risk. A quick Google search about RIFA capacitors will tell you all about them.

Unfortunately I also took apart another Tridonic ballast, this time a PC PRO 26/32/42 FSM b101 and I also spotted a RIFA PME capacitor also cracked.

Now I do not know if this topic has been covered on this website before and I have no idea if Tridonic have spoken out about this and I do not want to scare anyone but if you have these ballasts, please check if the capacitor is intact.

I have also taken apart a Tridonic PCA 1/40 T5c ECO ballast from 2011 and luckily it did not have a RIFA capacitor in it.

Thank you for reading.

Well, those damn RIFA capacitor plagued quite a lot of electronics made around 1980s-1990s. I myself removed a few recently, one from a vintage Apple IIgs power supply, and another from an old telecom protocol analyzer. So far, none of them gone smoke bombs before, just looked suspiciously cracked.

In practice, there is not much fire risk, especially in a metal ballast box, these usually just generate a lot of nasty smoke. Though, in Y capacitor position, there will be a shock risk!

I bet Tridonic will prefer to say nothing, as ballasts are loooong after any warranties, and also after the planned lifetime....

I recently learned that the Rifas (and Wimas) in audio/video stuff are actually a fire risk in specific but common situations.

I know of one person with a Revox tape recorder that has them as snubbers over the motor relays, who had his tape recorder catch fire. I know a bunch of others where they burnt out without consequence in the same model, but apparently this is no guarantee it won't catch fire when they go. These Revoxes are made out of chipboard. Sturdy, but apparently flamable enough to ignite with the not too big flame a Rifa/Wima produces when failing.

Another person had a TV with one in it catch fire. Chipboard, thin plastic rear cover.

In a metal ballast box, indeed negligible fire risk. But if it's in a chipboard or plastic housing mounted close to the plastic or wood, then there definitely is a fire risk.

Personally i had them fail shorted (which is the ideal condition because it will pop the breaker) but also fail half-shorted, blowing smoke everywhere. In the devices where they failed, fire risk was high in the vacuum cleaner where it failed without shorting out (dust!) but not too bad in some others (Toshiba T3200 laptop - the board is non-flamable, the plastics have the look of fire retardent containing plastics)

How these RIFA capacitors blows up? These aren't electrolytic capacitors.

These RIFA capacitors contain an epoxy casing which cracks over time allowing moisture to enter into the capacitor, make contact with the paper dielectric and boom.

As opposed to standard capacitors, they have paper dielectrics which break down over time. Always have done, always will do, regardless of the way they seal them. With one exception: paper submerged in oil, in a soldered shut metal can, typically actually lasts pretty long.
Any of the tar, wax or epoxy covered paper capacitors *will* fail. This is why old tube radios almost always need recapping.

Ceramic or plastic-dielectric caps don't do this.

Rifas are good at their job for as long as they aren't leaky. They perform better than some styles of plastic capacitors while actually being a fairly cheap option. But the failure mode of plastic capacitors is much safer than the failure mode of paper capacitors. Plastic and ceramic caps just don't burst into flames at the end of their useful life.

But imho there is no excuse to still use paper capacitors in the modern world. Even in the 2000s, those Rifas made in the 1980s were already burning out. The engineers should have known and not used the damn rifas. Even if they don't cause a fire, especially in big lighting installations they can cause a building evacutation which can cause significant loss of productivity that day (so, "lose" money).

RIFA PME capacitors are not notorious for the fact of them failing. They are "notorious" for the fact of making it visible

The most common other type of capacitor used nowadays are polyester X2 capacitors (from multiple manufacturers). Many of them last only a handful of years before failing, except they fail silently by electrically burning away the metallization on the film

Many of the polyester (and even the better polypropylene ones) have an explicit warning in the datasheet not to use in capacitor/zener divider applications. There is just too much "activity" inside, right from the start, for them to work reliably for any length of time in an application that expects a somewhat stable current source. They get used as EMI filtering capacitors because nobody (on the manufacturing side of home and office equipment) really cares about EMI after the device passed the initial testing

By the time a PME capacitor fails -  by its external potting cracking from age of the material and initiating the failure mechanism, it is mostly still ok electrically

(polyester Y capacitors must be more reliable than their X counterparts against failing shorted, so there maybe indeed they last - I have not checked the Y ones that much)

Polyester capacitors sometimes die in a non passive way, when their self healing mechanism fails, mostly when constantly a bit high line voltage meets a bit low quality capacitors. They keep melting and smoking and extruding melted plastic from holes burned in their case for a long while

All i have ever seen from a PME is cracking and a puff of smoke for a couple seconds, even when the remains of the capacitor remained connected to voltage immediately after the event



What i do with old equipment with PME capacitors in it - Acknowledge that for equipment from the 80s or 90s they lasted 30 to 40 years, and replace them with brand new identical PME for the next 30 years

The RIFA PME capacitors are still made nowadays, though there appear to have been some minor changes in the capacitor appearance, probably from when they moved the factory from Sweden to Finland. In particular the appearance of the metal foil cover over the actual capacitor roll, which is the 1st layer preventing the external cracking on the surface from propagating deeper inside. Maybe they actually resolved the problem with the potting material, but we will know only in another 10..20 years

The ultimate choice of capacitors for lasting forever is polyester (and other plastic films), but with big voltage margins - Like using 440V capacitors (instead of the usual 275V) for 230V applications. Maybe they do it in some very high end industrial equipment, but i don't recall anything like that in the average consumer or "light industrial" stuff



Most lighting ballasts have rated lifetime of 10 years. Indeed, the good ones can last many times that, but this does mean that the manufacturer won't be putting conscious effort into making them last longer than that

RIFA PME capacitors have been used through the 80s in Magnetic PerfektStart ballasts made by Knobel Ennenda (and Eltam). There they are hidden inside the relay case, wired between the input 230V phase and Neutral after the lamp filament

I have found several of them in the late 00's, dating from around 1981, so were 25 years old at the time. The capacitor inside is discolored and cracked from being for years right next to a hot heating element, but i never seen them short out (which would blow the lamp filament, so be noticable from outside by looking at installs with those ballasts, which existed here well into the 2010's). I think what prevented them from failing there despite being cracked, is that they were not exposed to the external environment, but to the clean and dry enclosed space inside the relay

It is generic problem for all paper capacitors. It is practically impossible to really prevent any moisture to seep in it, unless it e some special hermetic construction (molded plastic/epoxy cases aren't). With older vacuum tube electronic (old radio, TV, audio gear) a leaky capacitor can easily destroy the tubes, so it is often way better to just replace at least the critical ones (interstage coupling from anode to the grid of the next tube) before even attempting to power the thing up, if those capacitors are some of the paper type (paper wax, these Rifa ones,...).

RIFA PME capacitors are not notorious for the fact of them failing. They are "notorious" for the fact of making it visible

The most common other type of capacitor used nowadays are polyester X2 capacitors (from multiple manufacturers). Many of them last only a handful of years before failing, except they fail silently by electrically burning away the metallization on the film

Daim and Mex are some brands of plastic caps that tend to fail rather quickly. I've seen many of them which have lost their capacitance within 10 years of use. There are more. The only good thing about those, is that they don't go up in flames.

As you say, it is of the utmost importance for the engineer to check the datasheet for what applications they are suitable. Many of these are used as a series capacitive dropper. Slowly but surely they then lose capacitance and eventually cause the device to quietly fail. Philips had a major recall for their Senseo coffee machines that failed in exactly this way.
There are other capacitor types with different dielectric which are more resistant against big voltage spikes you can find on the mains. I don't know which ones. FKP, MKP, MKT...

Either way, for anyone replacing these things in lighting fixtures, get an X2 or Y2 type, and preferably a Wima, Panasonic or other good brand. I wouldn't put another Rifa PME back into it. It might last another 20-30 years which for some may be plenty, but if that fixture is sold to another person who doesn't know it, they might simply throw it away if it starts smoking.

My parents have thrown away a BEAUTIFUL kitchen mixer in my childhood because its suppression cap burnt out. They didn't know how to fix stuff and that it's not the motor that burnt out, so even if you get it to a professional repair person it would be a cheap fix, and i was 10 or so so i could take it apart but i didn't know what caused the smoke. It was a very heavy AEG machine, early 70s, very powerful. I somehow remember the chassis as being made from ceramic, but it may also have been white bakelite.

Yes had this with several Tridonic's of this era, the first one I came across was a 1994 PC 2x16 C001 which tripped the RCD within a few minutes of being powered. Of course new caps sorted the problem and for now the electrolytic cap seems to be ok after 30 years storage.

I've had several others from the late 90's and early 2000's that I have replaced the Rifa's in too, most recently these PC 36 E011 IDC ballasts from 2002. Now I've started replacing them with a Rifa PHE 850 plastic film cap which seems to do the same job and hopefully won't degrade in storage in the same way the PME ones did.

The newest one I have come across is this EM 36 ST self testing emergency module from 2010 that had a pair of them in which had also cracked, again replaced them with some plastic film equivalents. Not sure what the purpose of them in that one was as they are not on the input end but rather around the lamp disconnection relays instead.

It is always worth opening up any Tridonic HF ballast from the 2000's or older and checking for them as its quite annoying to install the ballast and later have issues with RCD tripping due to the capacitors failing.
It seems by the mid 2000's in the new PC PRO ranges they switched to a plastic film cap similar to the ones I have started fitting as replacements for the failed PME's, but the older PC C001 and PC E011 ranges are almost certain to contain them.

Ah yes, another beautiful example of these damn RIFA Caps!!!  I have had problems with COUNTLESS.  I repair and restore audio amplifiers as another hobby of mine, and these capacitors are used in quite a lot of them. They are pure garbage!    Moisture gets inside of them, and then it is game over.  I had a few larger examples explode and fill the whole room with smoke, like a smoke machine! It was seriously impressive. But it created a huge oily mess to clean up afterwards, heh .I always replace these now, they are way past their prime to say the least I think they were fairly cheap when new, so they probably never were the greatest quality. 

Nothing beats a metal can capacitor that is properly sealed, I run a lot of filter and PFC capacitors from the 1950-1960's daily and have done so for countless years at this point without a single problem! ''Super-Purity Chlorinated hydrocarbon impregnation'' keeps the moisture at bay, still to this day!  Properly fused and protected, a explosion is unlikely in the event of a failure.

Old capacitors are ALWAYS better than new ones, except for paper and foil caps (and RIFA cubes like these!) that love to get electrically leaky and screw things such as tube-circuits up! I always replace those with Poly-film caps instead. But filter and PFC capacitors that are metal can types... If they are good, I keep them

I have put thousands and thousands of hours on the original filter capacitor in my daily use amplifier from 1957  

Lets have a look at some other capacitors

https://www.we-online.com/en/components/products/pbs/capacitors/film_capacitors/info

Go down to the FAQ at the bottom - "Can X2 caps be used in series with the mains ?"

Some applications called capacitive power supply or transformerless capacitive dropper use X2 capacitors in the input line (between mains power and the load). This use is called “in series with the mains”.
For this application, special THB X2 capacitors with explicit confirmation of this application must be used. We confirm this for certain types by specifying “Across the mains or in series with the mains” under “Application” in the data sheet. Würth Elektronik offers X2 THB film capacitors under the series WCAP-FTXH.

Seems very standards and ratings related, unless....

THB is not just some name of a series of capacitors. It stands for Temperature Humidity Bias - testing in which the capacitor life and reliability are tested under conditions of Temperature, Humidity, and Bias (applied voltage)

Yep, they are also concerned about humidity. From a manufacturer that does not make and never made paper capacitors

Wait a sec.. So to work in a capacitor/zener application, the capacitor must be one specifically made to last under THB conditions, but for plain X2 application for EMI filtering (which is definitely not any better working condition in terms of applied voltage/transients), all of that is not needed ?

EMI testing (to get certification for the product the capacitor is installed in) is performed on the 1st sample unit of the product and takes a few hours. (Assuming the unit may be powered for other testing and demonstrations before it arrives for EMI testing, make that a few months). Nobody will notice that it went missing afterwards. That is exactly as long as the EMI filter capacitors are required to last in the eyes of product manufacturers

This won't work for a capacitor which actually matters for the functioning of a product, which will result in mass warranty claims and recalls



For capacitors which design is older than some of the tests in question, yet actually last and stay in spec for the first 20 years, Rifa PME are anything but garbage

They are what they are - compact "metallised film" (assuming paper is a film) capacitors which are electrically fairly good, but have a unique other fault mechanism which is non electrical in its first stages, before it progresses into an electrical fault



The reason why old capacitors last long electrically is the low extent of process control in theirmanufacturing. Let me explain :

Life of film capacitors has a very strong relation to voltage. Life is proportional to (Vapplied/Vrated)^n, where values i seen for n = 7, 8, 10, 20 acc. to different sources (varies by film material, thickness, and individual manufacturers)

With older processes the film thickness uniformity, and risk of existence of pinholes, were not very precisely controlled. So they were made with overkill film thickness in the 1st place to guarantee that they work reliably

In PME capacitors it is also the fact that the dielectric is paper, naturally a fibrous and not very uniform material, which again results in some more margin taken in the design

All capacitors with metallised film technology (maybe except the earliest ones) have a self healing mechanism - Blowing up of metallisation around pinhole film breakdowns, allowing the capacitor to continue working after such event. In contrast, in foil capacitors every isolation breakdown is immediate full failure by shorting out

In modern capacitors the precision with which the film can be made (thickness, uniformity, cleanliness), and precision of models to estimate its life, allow to shrink it to exactly the thickness at which it will survive the rated voltage, with the self healing mechanism "ticking" just slow enough to be acceptable for an intended rated life

In most X2 capacitors nowadays the film is so thin that corona discharge around the edges of the metallization pattern (think of it, sharp edges of a metal layer of the thickness of microns-scale coating) becomes equally significant factor in the destruction of the metallization. They arent even "ticking" anymore, they just burn away continuously

The self healing mechanism really works exceptionally well if with all this, we don't see the modern capacitors explode and go up in smoke every day. But it too has its limits. Once in a while there will be a modern X2 capacitor completely melted

Kemet (the ones who took over production of the PMEs afaik) also mentions the across/in series with distinction in their product datasheets.

I kinda want to buy a batch of those SMD paper capacitors of them. Put a bunch in parallel with a fast fuse in series, and see how long they'll last. What stops me from doing that is that those things are still about €1,50 a pop in consumer amounts, and i want a decently large sample size...

I have seen one plastic dielectric cap that had gone up in smoke. It was a tubular one with 'straight' ends, no brand name on it. Oddly, in a Behringer PA subwoofer crossover filter. I don't know what went wrong in that PA rig, i wasn't there, but that capacitor had a big mushroom of carbonized resin bulging out of it. Many speakers were blown that night. But that still is the only catastrophic failure of a non-paper capacitor i've encountered.

Have a look at 2 series from Kemet :
https://content.kemet.com/datasheets/KEM_F3001_F861_X2_310.pdf
https://content.kemet.com/datasheets/KEM_F3092_F862_X2_310.pdf

One with the warning, the other rated specifically for the series applications. Same standards/approvals and ratings (except the automotive Q200, which is not directly an electrical rating, but only addresses the number of failures allowed/1 million units)

The big difference is in the "environmental test data" table

If you pick one capacitor value that exists in both series, you'll see the difference in its dimensions - They have different film thickness inside

The more common 275V X2 and X2 mini series from Kemet (for which i don't know whether a matching "series applications" series exists) also have this warning :
https://content.kemet.com/datasheets/KEM_F3093_R46_X2_275_110C.pdf
https://content.kemet.com/datasheets/KEM_F3094_R46_X2_275_110C_MIN.pdf

PME don't have the warning and dont mention specifically series applications either, they vaguely state "all X2 applications" :
https://content.kemet.com/datasheets/KEM_F3011_PME271M_X2_275.pdf

I've just been replacing some more of these Rifa caps this afternoon.
Firstly a pair of them in a 1999 Tridonic PC 30 C001 ballast, the originals appeared ok when I got the ballast but when I opened it to check today they had cracked so I replaced them with a pair of plastic PHE 850's.

Second was another Tridonic EM 36 ST emergency module from 2010 with a couple of different sizes of them, both replaced for PHE 850's of the same ratings which will hopefully prevent any future issues.