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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 2nd Sep 2012, 7:53 pm   #61
Kat Manton
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Default Re: Beware Rifa Class X Capacitors!

Another addition to this rogues' gallery, a couple of Rifa X2 capacitors, marked 'PME 271 M 610'.

The following exhibits were in the Taiwan manufactured Phihong Model PSA-523BU switch-mode power supply, installed in the Linn 9000 I'm currently restoring (which dates from 1985 going by IC date codes.)

Before I tried powering it, I took the PSU apart to give it a quick visual check, resolder dry joints, and wave my ESR meter over the electrolytics. Due to the densely-packed board I didn't notice the 'Rifa' branding, and from above, they looked okay...

Two hours into soak-testing the PSU, out of the unit, into a dummy load, there was a loud crack followed by a fizzing noise and a huge cloud of evil-smelling smoke erupted. That was over a week ago and I can still smell it!

My camera has a nifty 'super macro mode', so I tried to get some good close-up pics:
  1. Exhibit A, type number etc.
  2. Exhibit A, underside.
  3. Exhibit A, other side, showing approval markings.
  4. Exhibit B, the unexploded capacitor of this type, showing the typical cracking.
  5. Replacement capacitor. Same type (it's all I could find that will fit.) I hope they've changed the epoxy encapsulation...

Kat
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Old 2nd Sep 2012, 9:08 pm   #62
Lucien Nunes
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Default Re: Beware Rifa Class X Capacitors!

I have had a few Rifa X-caps fail like that but they were all from the 1980s. The first two were both in vacuum cleaners, one only a few years old when it failed. Whenever I see one I instinctively look for cracks but it is a long time since I spotted any in a component in active service that would most likely be of recent manufacture.

Perhaps the same situation occurred as with Hunts Moldseals, a commercial grade of capacitor that required a low-cost encapsulation, for which the material chosen did not ultimately meet expectations. Maybe they skimped on the accelerated life tests, or maybe the tests didn't cause the same degradation that has occurred in reality, you would have hoped for a bit more resilience from a part targeted at a safety-critical application.

A good idea, testing the PSU separately. I think this practice will become more common as we see an increasing number of electronic devices in preservation that incorporate self-contained SMPSUs. The 1970s-80s trend towards modular power supplies has the happy result for us that one of the most troublesome parts of machines like this can be substituted outright by a modern equivalent without affecting the originality of any part except the PSU itself.

Lucien
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Old 2nd Sep 2012, 10:13 pm   #63
Leon Crampin
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Default Re: Beware Rifa Class X Capacitors!

I made a comment earlier in the thread concerning the usefulness of testing houses and approvals - my point being that with about £30 worth of test gear I was able to show that these components were unsuitable for the intended purposes of my employer.

Surely the fact that approvals for these components have not been withdrawn makes the whole scheme a joke.

Leon.

Last edited by Leon Crampin; 2nd Sep 2012 at 10:15 pm. Reason: Punctuation.
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Old 2nd Sep 2012, 10:58 pm   #64
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Default Re: Beware Rifa Class X Capacitors!

Thanks Kat for putting up these photos.

I'd be a bit surprised if there were no other X capacitors that would fit, in a 'proper' package (moulded plastic box with toughened epoxy fill), but then I haven't looked.

Whether Rifa have changed the epoxy or not, my confidence would be on the low side, whatever! The internal capacitor element is zinc-metal listed paper, and any moisture ingress is as bad as the old waxies. Only if the capacitor element is immune to moisture (as was the case with wax-finished mica capacitors), such that failure of the encapsulant didn't immediately render the component life-limited, would I be happy long-term.
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Old 3rd Sep 2012, 11:34 am   #65
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Default Re: Beware Rifa Class X Capacitors!

I had to buy more X2 & Y2 caps today and was tempted to buy Rifa because the other brands in the Elements14 (Ex Farnell) catalogue didn't seem to have the same pedigree of Type Approvals.

My logic there being that the originals in my application have lasted 20 years or more of 24/7 use, so I wouldn't be bothered when they died the next time around, but commonsense prevailed and I bought some nice blue encapsulated types instead. I'm hoping they don't disappoint................

Cheers

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Old 3rd Sep 2012, 3:19 pm   #66
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Default Re: Beware Rifa Class X Capacitors!

Other Vintage Radio posts about Rifa capacitors are here https://www.vintage-radio.net/forum/...t=86493&page=2

Rifa mains capacitors have been failing en masse for more than 20 years. I am aware that capacitors manufactured in the 70s, 80s, and 90s, are affected (more recent units may be also, I don't know - yet). You may be quite sure that Rifa/Kemet are very well informed about it. The premature failure of Rifa capacitors has adversely affected the reliability of huge numbers of equipments from many major companies and others. Obviously, in such circumstances, there has no doubt been legal action behind the scenes.

While the Rifa capacitors have approvals from many safety authorities, the approvals do not generally relate to product life expectancy. If units have a life of only 5 or 10 years this is not a safety matter - so long as the units fail without danger. The philosophy seems to be that the capacitors satisfy all specifications, it's just that they have an inbuilt mechanism which gives them a short life.

If you decide to challenge this philosophy you had better be prepared for legal argument. I would not be surprised if you first have to prove that you indeed have a Rifa capacitor and not an indistinguishable copy. Also, you had better have the receipt from an authorised agent. Purchasers of Rifa/Kemet products should be aware of the legal limitations that the company seeks to impose (quoted from website and data sheets) and thereby minimise its liability:

"Over the past decade, the number of non authorized sources for electronic components including KEMET Capacitors has greatly increased. These sources range from individuals selling electronic components out of their homes, to large web-based traders and independent distributors/brokers. There is no way to conclusively determine the storage/handling conditions and legitimacy of origin of products bought through non authorized sources. Product supplied through non authorized sources may appear to be legitimate, but many quality issues with such product can occur and KEMET cannot warrant product purchased through non authorized sources.

"Customers that buy KEMET Capacitors from non authorized sources may save money in the short-term, but they run the risk of major reliability issues that can damage their reputation and prove enormously expensive in the long-term due to warranty expenses, field replacements, and liability claims. Customers that nonetheless turn to non authorized channels for KEMET Capacitors trade risk for reliability. For these reasons, KEMET Corporation strongly encourages all our customers to buy our product exclusively through our authorized sources.

"Statements of suitability for certain applications are based on our knowledge of typical operating conditions for such applications, but are not intended to constitute – and we specifically disclaim – any warranty concerning suitability for a specific customer application or use. This Information is intended for use only by customers who have the requisite experience and capability to determine the correct products for their application. Any technical advice inferred from this Information or otherwise provided by us with reference to the use of our products is given gratis, and we assume no obligation or liability for the advice given or results obtained."


I am not aware of any significant problem with any other brand of mains capacitor and all other brands in my experience, have a normal long life.

Peter
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Old 3rd Sep 2012, 6:44 pm   #67
Leon Crampin
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Default Re: Beware Rifa Class X Capacitors!

Sounds like a smoke screen - appropriately enough.

The things are not fit for purpose. I rest my case.

Leon.
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Old 3rd Sep 2012, 8:19 pm   #68
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Default Re: Beware Rifa Class X Capacitors!

The usual legalese back-covering exercise, or pseudo justification of the pricing effects of distributorship contracts.

So their capacitors are very demanding of the environments in which they're stored are they? That would seem to disqualify them for fitting into products that go outside of their distributors' nicely air-conditioned premises.

Methinks their very disclaimer is a large-calible (calibre) shot straight through their own foot.

David
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Old 4th Sep 2012, 12:14 am   #69
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Default Re: Beware Rifa Class X Capacitors!

I too have had my share of these capacitors exploding for no readily apparent reason; I've nothing to add on that score to what has been said above. But the following made me pause to consider . . . .

Quote:
Originally Posted by Radio Wrangler View Post
So their capacitors are very demanding of the environments in which they're stored are they?
David
Which, to me, seems are very fair assessment of what they are actually saying. But isn't that statement - as translated by you - putting the cart before the horse? Surely it is the 'environment' that places demands on the component, (not the other way around) and with the specifications for that component stated, read and understood by the user, that user will store or fit that component, and employ or store it in an 'environment' as specified by the manufacturer. Subsequently he will relax and forget it with confidence, since he has, by definition, met the manufacturer's 'conditions of use': storage and fitment.

My conclusions: I agree with David's comments above (1st. and 3rd. paragraphs above) and Leon's post previous to that.

Al.
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Old 4th Sep 2012, 12:49 am   #70
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Default Re: Beware Rifa Class X Capacitors!

Sorry, I was laying irony on by the trowelful, hence the direction of demand.

All the disclaimers on shrink-wrapped software similarly translate as: "If the manufacturers have so little trust in their product, AND they go to such lengths (literally) to tell me so, then I'd be a right fool to buy it." They can be simplified to "This product is crap" And they try to force people to read it before said people buy it.

David (from my avatar, I've got a definite preference for where to put the horse. The intelligent looking one of the pair of us is called 'Big Corrie')
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Old 4th Sep 2012, 2:29 pm   #71
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Default Re: Beware Rifa Class X Capacitors!

What warranty does Kemet offer on their mains capacitors?

The short answer (avoiding legalese) is that the product will conform to product specifications at the time of shipment. There is no warranty as to how the product will perform in a month or a year - let alone 10 years.

In addition, any warranty of merchantability, and any warranty of fitness for purpose, are specifically excluded.

What exactly are the particular handling/storage conditions referred to in the disclaimer? These are rather elusive and do not appear to be specifically stated by Kemet anywhere, for mains capacitors. Insofar as they may be similar to other Kemet capacitors, the conditions would be that "the capacitors can be stored anywhere from -55 degrees C to 125 degrees C. However, it is a good idea to store them in areas generally suitable for human habitation with respect to maximum temperature. Areas involving corrosive gases or liquids should also be avoided."

These storage conditions would probably be met by most "web-based traders"!

Peter
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Old 11th Sep 2012, 11:33 pm   #72
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Default Re: Beware Rifa Class X Capacitors!

X2 capacitors can explode without any power being applied as I have found out.
Me thinks it is something to do with the resin they are encapsulated in.
I am investigating it and have not had time to get it all sorted out as the problem has nabbed the power from the spell checker, however an early report can be seen on a link.
http://vintagetvandradio.myfreeforum...hp?f=17&t=2868
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Old 12th Sep 2012, 12:03 am   #73
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Default Re: Beware Rifa Class X Capacitors!

I think 'explode' is a bit dramatic, 'split in half' is what I'd call it!

These Rifas need binning, end of story.
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Old 12th Sep 2012, 2:13 am   #74
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Default Re: Beware Rifa Class X Capacitors!

Like when an atom is split in half?

Peter
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Old 12th Sep 2012, 3:57 am   #75
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Default Re: Beware Rifa Class X Capacitors!

I was doubly shocked because it was not a Rifa.
That kind of resin coupled with time may have something to do with it.
They need a do not plug in after date printed on them and and equipment they are used in also needs the same.
They are safety components after all and like washing machines with there 5 amp door switches and 10 amp boil wash elements go into the safety parts are more of a hazard than the rest of the appliance box too.
It is not just Rifa capacitors, there are plenty more dodgy safety parts out there.
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Old 12th Sep 2012, 12:21 pm   #76
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Default Re: Beware Rifa Class X Capacitors!

I think there is some continuing misunderstanding as to the purpose of 'safety' components and the meaning of those approval markings.

These components can (and do) fail, and are permitted to do so. What matters is that should they fail, they do not result in, say, the equipment they're in setting fire to your house or the casing becoming live and electrocuting someone.

If I'd been out of the room when the capacitor above failed, I suspect it would have continued to smoke for a while, until the current it consumed increased enough to cause the fuse to blow.

Don't assume those safety markings mean a component is high quality and will last indefinitely. Generally they cover such things as the component encapsulation (circuit board, wiring insulation etc.) being made from fire-retardant or self-extinguishing materials. This ensures that, after removal of power (fuse failure), the equipment doesn't continue to smoulder, doesn't eventually burst into flames some time later and doesn't burn your house down.

Kat
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Old 12th Sep 2012, 4:21 pm   #77
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Default Re: Beware Rifa Class X Capacitors!

I used them in my dimmers at the theatre. I had so many fail that I do not use this type any more.

Dan.
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Old 15th Sep 2012, 9:41 pm   #78
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Default Re: Beware Rifa Class X Capacitors!

Here's another one for the rogue's gallery.
A college at work asked me too have a look at his wife's sewing machine, smoke had apparently started coming out of the pedal whilst she was using it. Opon opening the pedal (harder than is sounds) I found the cause right away. Changing the cap for a modern X2 out of a scrap PSU was all that was needed.
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Old 15th Sep 2012, 11:44 pm   #79
Leon Crampin
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Default Re: Beware Rifa Class X Capacitors!

I have mentioned this in another thread - but perhaps a timely reminder.

If anyone has a Quad 33 pre-amp which they would rather not suffer from severe smoke damage and a welded mains switch, I would respectfully suggest that they remove the Rifa click suppressor which Quad fitted behind the mains switch.

The click suppression is no different without the capacitor - sometimes it does and sometimes not, according to when in the mains cycle you operate the switch.

Leon.
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Old 23rd Sep 2012, 11:23 pm   #80
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Default Re: Beware Rifa Class X Capacitors!

well I thought this looked a bit wrong when I bought it from the shop recently, I wont be using this then, next time I'm passing the shop I will mention this thread.
this hasnt ever been used, is NOS
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