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Old 26th May 2011, 7:41 pm   #41
kalee20
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Default Re: Beware Rifa Class X Capacitors!

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Originally Posted by Philips210 View Post
I have also noticed fine cracks in the case of some Rifa class X2 capacitors so wondered whether moisture could be to blame.
Me too - see post No. 2. I'm glad I'm not the only one!
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Old 26th May 2011, 7:52 pm   #42
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Default Re: Beware Rifa Class X Capacitors!

Me too I had 250 NOS of the blighters in stock , after all the evidence, last week I replaced them with new X2's.

Chris

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Old 26th May 2011, 8:09 pm   #43
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Default Re: Beware Rifa Class X Capacitors!

I should mention that my recovered samples had hairline cracking and a megger test gave less than 10 meg insulation at 500V. Frankly appalling and definitely not fit for purpose.
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Old 26th May 2011, 8:38 pm   #44
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Default Re: Beware Rifa Class X Capacitors!

Is this problem noted with other makes of X type caps?
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Old 26th May 2011, 8:48 pm   #45
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Default Re: Beware Rifa Class X Capacitors!

I have just done a 500 Volt insulation test on a handful of these caps (various values but mostly 100nF) and they all tested around infinity so would appear fit for service. The fine cracks in their cases do however make me doubt their reliability and I will not be using them.
These capacitors have been stored in my dry workshop. It might be interesting to repeat the insulation test after they have been subject to high humidity.

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Old 26th May 2011, 9:13 pm   #46
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Default Re: Beware Rifa Class X Capacitors!

This brings me back to a post I made way back in the thread. Mains filter caps have always been troublesome. The fix for many years was a 0.1uf 1000v DC cap usually a RS or a Duramold. In a TV they lasted a good few years but when they went faulty inevitably they went short circuit blowing the mains fuse.
Now I don't really see that the modern cap is that much better than what we used in 70's & 80's.
What worried me in post 1 was the amount of heat generated and what consequences might have happened if I had not been there.

One thing that comes to mind is it's all very well doing an insulation test but these caps are often across the mains constantly as they can be fitted on the un switched side of the mains so are subject to supply constantly. A year or so ago I posted a thread about power wastage and was abruptly told I was wrong, but I am sticking to my guns as I have come across many X type caps running warm in microwave ovens and other consumer electronic devices. A cap should not run warm in this position and the old 1000v ones never got warm.
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Old 26th May 2011, 9:43 pm   #47
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Default Re: Beware Rifa Class X Capacitors!

I've just replaced 4 Rifa caps in the Revox I'm working on. Although they weren't X types they did have significant AC volts across them in the motor control circuits. 3 of the 4 have cracks in the case. Probably better safe than sorry.

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Old 26th May 2011, 10:06 pm   #48
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Default Re: Beware Rifa Class X Capacitors!

I think capacitor technology is mostly superior to the 1970's. The old Dubilier 'mixed dielectric' capacitors used as mains filters and boost reservoir capacitors were very troublesome but were good for the repair business.

The modern mains filter capacitors (class X2) are generally trouble free apart from some of the Rifa examples highlighted in this thread. I haven't found any other makes of mains filter capacitor giving any trouble in recent years.

Although off topic (maybe the basis of further discussion in a separate thread), other fairly recent capacitor problems include those troublesome Panasonic disc ceramics, dangerous multilayer caps and some of those blue high voltage ceramic caps that fail more often. I nearly forgot about those terrible surface mount electrolytics that leak over the pcb causing severe damage to the board (Canon camcorders spring to mind).

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Old 26th May 2011, 10:18 pm   #49
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Default Re: Beware Rifa Class X Capacitors!

Too true about the little surface mount caps, During my time with Sony I must have replaced literally thousands!

So what we seem to be saying, Rifa is the bad egg. So what makes are good and reliable?
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Old 26th May 2011, 11:59 pm   #50
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Default Re: Beware Rifa Class X Capacitors!

The ones you can't remember name of as you never ever had to replace them
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Old 2nd Jul 2011, 9:45 am   #51
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Default Re: Beware Rifa Class X Capacitors!

Just had a RIFA X2 capacitor fail on my Philips scope filling theworkshop with clouds of smoke.

Two things that occurred to me:

1) The scope hadn't been used for some time, possibly 2 years

2) The capacitor is rated at 250V where as the mains in the UK is 240V and sometimes going as high as 245V which is perilously close to its max rated voltage.
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Old 2nd Jul 2011, 10:16 am   #52
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Default Re: Beware Rifa Class X Capacitors!

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The capacitor is rated at 250V where as the mains in the UK is 240V and sometimes going as high as 245V which is perilously close to its max rated voltage.
If it's X2 rated all the mains tolerance issues etc are meant to be taken into account regardless of any marked voltage rating. The problem with the RIFA caps is that were just badly made and should never have got the approvals in the first place.
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Old 2nd Jul 2011, 12:24 pm   #53
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Default Re: Beware Rifa Class X Capacitors!

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Originally Posted by Michael Maurice View Post
Just had a RIFA X2 capacitor fail on my Philips scope filling theworkshop with clouds of smoke.

Two things that occurred to me:

1) The scope hadn't been used for some time, possibly 2 years

2) The capacitor is rated at 250V where as the mains in the UK is 240V and sometimes going as high as 245V which is perilously close to its max rated voltage.
Yep, ditto - My Philips 'scope did the same, after a period of inactivity as well, and was removed out to enable me to continue (note to self: must remember to fit a suitable alternative).
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Old 2nd Jul 2011, 7:02 pm   #54
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Default Re: Beware Rifa Class X Capacitors!

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The problem with the RIFA caps is that were just badly made...
And, I hasten to add, badly designed as well.

I had the doubtful priviledge of having a Rifa rep visit, mid 1980's, extolling the virtues of the metallised paper construction using zinc metallising. Self-healing, improvement of insulation resistance with each self-healing event, one-piece voidless transparent epoxy encapsulated construction rather than a plastic box filled with opaque resin, were all proudly plugged.

Shame he didn't mention that the epoxy cracks, lets in moisture which the paper then absorbs, the zinc metallizing corrodes, and the thing catches fire...
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Old 10th Jul 2011, 12:19 am   #55
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Default Re: Beware Rifa Class X Capacitors!

I was wondering about the range of equipment these capacitors are fitted in and are these capacitors still available? One would think that if they are still on the market, then they would have been modified in their construction.

So far it seems the capacitors have only smoked and not caught fire so the materials are probably safe. (self extinguishing?).

Thanks for the tip on the Philips scopes, I'll check mine to see if a Rifa cap is fitted though I would have thought that Philips would have used one of their own.

Recently I purchased quite a few oldish NOS components from our local car boot sale and among them was about ten 100nF Rifa class X capacitors. They were all cracked, some quite severely so. I knew that I wouldn't be using them but out of curiousity checked the insulation resistance. Most of them read around 1M Ohm and some less than 500k Ohm. I thought about running a mains lead in a box out into the garden with one of the caps across the mains as an 'experiment' but thought better of it and threw them out instead!

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Old 10th Jul 2011, 8:20 am   #56
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Default Re: Beware Rifa Class X Capacitors!

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One would think that if they are still on the market, then they would have been modified in their construction.
Yes that's a good point. The same can be said about 'Wima' that were the bane of many engineers in the 60's/70's when these 'toffee' shaped capacitors were used prolifically in Grundig tape recorders. They were almost a 'change on site' component especially when used as a coupling capacitor....invariably they failed s/c, not just leaky! However much later 'Wima' capacitors that I have seen are as good as any other polyester types.....it's just the name that made me have reservations.

It's possible that 'Rifa' have now been bought out by another company and are every bit as good as any other.


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Old 10th Jul 2011, 8:38 am   #57
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Default Re: Beware Rifa Class X Capacitors!

Here's a comparison the one on the left taken from a batch of the ones which seem to fail, you can see all the fractures in the envelope. On the right a newer one.

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Old 10th Jul 2011, 9:03 am   #58
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Default Re: Beware Rifa Class X Capacitors!

They look alarmingly similar !

I guess a small tap with a toffee hammer would be a good test for how brittle the encapsulation is on old vs modern.
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Old 11th Jul 2011, 12:50 pm   #59
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Default Re: Beware Rifa Class X Capacitors!

No no no - you want a thumping great sledgehammer. And a lumberjack. Then they'll be beyond causing trouble.
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Old 1st Aug 2011, 11:27 pm   #60
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Default Re: Beware!

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I am beginning to think X caps are not what they are all cracked up to be!
The Rifa ones are certainly 'cracked' up!

Symon.
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