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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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24th Sep 2012, 12:35 am | #81 |
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Re: Beware Rifa Class X Capacitors!
Have you any idea how old that one is?
It looks like it has quietly exploded while in storage just like the two WYMAs that i have found. |
24th Sep 2012, 3:41 pm | #82 | |
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Re: Beware Rifa Class X Capacitors!
Quote:
Spot-on Kat! Failing safely is what we call it. When we safety test though, we don't assume that just because a component has safety marks that it is safe. We have to see the approvals from the respective test houses before we accept it. There are so many fake parts out there with fake approval marks. Rich.
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25th Sep 2012, 10:02 am | #83 |
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Re: Beware Rifa Class X Capacitors!
I, too, have been witness to a fair few of these letting go with anything fron a gentle hiss to an attention-getting pop and inevitable accompanying smoke-screen. Every time, it has been very benign- smoke clears, kit is still working, I don't even recall low-value equipment fuses blowing. A few minutes replacement work and maybe a bit of "nicotine stain" around very adjacent components and PCB. So, in a stringently "Mr. Logic" fashion, they have not "failed" because they have fulfilled their compliance requirements.
However, whilst we know to "keep calm and carry on", a more representative proportion of the public- the man (or woman) on the street, Clapham omnibus etc., etc. is wary, even fearful of electricity (and absolutely fair enough). "Jeez- it blew up in a big cloud of smoke, I switched off before it burnt the place down and took it down the tip- I'm not buying another Blogginex". This represents unnecessary waste and bad reputation- which is surely "failure" in most people's book, Colin. |
25th Sep 2012, 10:14 am | #84 | |
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Re: Beware Rifa Class X Capacitors!
Quote:
With a few exceptions, I'm certain very few people would be happy carrying on using something that's gone bang and emitted smoke, and the majority of those would prefer to replace the item because of safety concerns. Nick. |
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25th Sep 2012, 11:39 am | #85 |
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Re: Beware Rifa Class X Capacitors!
It still counts as a failure because once the smoke has cleared it will be open circuit and noise will be able to pass along the power cable.
They were unlikely to have been made to last longer than 10 years from new. |
27th Sep 2012, 10:41 am | #86 |
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Re: Beware Rifa Class X Capacitors!
Hi Refugee, I was being heavily tongue-in-cheek, imagining the response of a notional Rifa spokesman to what is doubtless a veritable tsunami of disgruntledness,
Colin. |
27th Sep 2012, 12:00 pm | #87 |
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Re: Beware Rifa Class X Capacitors!
I would just like to see the things marked with a shelf life and operating life so that they can be replaced before they cause a stink.
The WYMAs i found were off having failed due to the shelf life having run out. |
27th Sep 2012, 12:13 pm | #88 |
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Re: Beware Rifa Class X Capacitors!
Interesting that they were actually shelf-lifed, at least an implication that storage could be an issue. Maybe being installed in something is slightly warmer and drier, time-averaged, than even a pampering shelf.
Considering that Rifas sport more badges of all-round worthiness than Idi Amin's chest, you'd think that someone, somewhere would specify "best before" consideration. |
27th Sep 2012, 12:52 pm | #89 |
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Re: Beware Rifa Class X Capacitors!
Hi
I see - the definition here is when (not if!) these components fail they do so in a safe and controlled way. Like many posters here I was under the erroneous impression that a safety component was there to ensure the unit performed safely - in the case under discussion that would be to filter mains-borne noise and transient spikes. Of course it's obvious when I think about it - a safety resistor is there to go open-circuit under excessive load conditions without further damage. I have in the past had to retrieve a wet set from someone's garden - understandably they were so scared of all the smoke they threw it out and drenched it! It's strange to think that these capacitors are still around as the construction fault is so well known. Glyn |
27th Sep 2012, 1:15 pm | #90 | |
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Re: Beware Rifa Class X Capacitors!
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Time for a check I think! Rich
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27th Sep 2012, 5:05 pm | #91 |
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Re: Beware Rifa Class X Capacitors!
This RIFA failed today and was unfortunately backed up by a 125A fuse which it blew.
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27th Sep 2012, 5:21 pm | #92 |
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Re: Beware Rifa Class X Capacitors!
What a filthy mess.
Did it damage the little black transformer or was the PCB scrap? The power devices look like they have been salvaged before i asked. |
27th Sep 2012, 8:00 pm | #93 |
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Re: Beware Rifa Class X Capacitors!
The PCB will be repaired (by me). The power devices are all fine, they are dual thyristors but they are still on the heatsink on the machine as it weighs more than a planet. Most of the problem, like with other Rifa damage, is cosmetic. I hope!
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27th Sep 2012, 8:59 pm | #94 |
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Re: Beware Rifa Class X Capacitors!
The soot is oily and requires a lot of elbow grease to remove it.
In a commercial situation it could involve the board being scrapped due to the time involved. |
27th Sep 2012, 10:44 pm | #95 |
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Re: Beware Rifa Class X Capacitors!
This is a commercial situation..it's a 45kW spindle drive on a CNC lathe.
The RIFA smoke deposits have been removed with MEK and a paintbrush. Vintage equipment owners should note that MEK will dissolve most plastics. I will of course be replacing all the Rifas with Polypropylene Film! The owner said the machine had been working continuously since the early 1990's and was turned off for two weeks for the first time. When they turned it on, there was a loud bang. He replaced the 125A supply fuses and it worked for another hour before going bang again and smoking. That's when they noticed the melted rifas!
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28th Sep 2012, 12:54 pm | #96 | |
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Re: Beware Rifa Class X Capacitors!
Quote:
It' is very common fo a power supply kept on the stores shelf for a couple of years to fail dramatically when it is put into service as I'm sure you are well aware Kevin. The failure to pre-condition power electronics such as power supplies and drives was a major cause of lost production in one plant I was responsible for.
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28th Sep 2012, 1:19 pm | #97 |
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Re: Beware Rifa Class X Capacitors!
Hi Kevin,
Can you please post some photos of the "good" Rifas when you remove them from the board. Plainly they are all about to go and it would be interesting to see how cracked the cases are. Peter |
29th Sep 2012, 6:15 pm | #98 |
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Re: Beware Rifa Class X Capacitors!
Wima Durolit caps might have some similar traits. Dad's Wurlitzer electronic organ (made in 1978) was found power-dead recently with no external symptoms other than an open 5A plug fuse. Internally, one of the amplifiers was found to have a dead T2.5A AC fuse and a failed Wima Durolit resin-cased paper capacitor across the line. This is an axial 0.047uF part rated 630V DC, 250V AC, certified by VDE with class X indicated in German. A small amount of material had been ejected from the end of the cap although there was no sign of major heating having occurred or resulting smoke damage, probably thanks to the energy limitation occurring in the two relatively low value fuses. The case of the capacitor had the telltale surface cracks in the thin area over the wound element. Another amplifier chassis was removed from the organ for comparison and found to have an intact Durolit capacitor without any sign of cracking, however the need to replace all such types was clear.
The organ was made in the US in 1978 primarily for the US market. Like many of its kind it is a single-voltage machine on which you would need to change motors and transformers to adapt between 115V and 230V voltage ranges. As the US 115V version had a lower voltage rating of cap in this position and of all the 2000 or so capacitors in the organ this is probably the only non US-made one, I suspect the Wima caps were fitted exclusively for the European market. I wonder how it would have fared with a 600V DC rated Sprague equivalent as I have seen fitted to other US-made export kit from the 70s? Lucien |
29th Sep 2012, 6:28 pm | #99 |
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Re: Beware Rifa Class X Capacitors!
Lucien has got a pair where one has failed first and the other is on its way.
They just time out just like my two radial ones. There may be some value in cracking the date codes on them. It looks like these WYMA and RIFA caps are made of the same stuff. Some of the other WYMA types appear to be all right. Even Hunts electrolytic types are OK it is just the wax and mould seals that are bad. |
29th Sep 2012, 7:38 pm | #100 | |
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Re: Beware Rifa Class X Capacitors!
Quote:
That's just like this one:- https://www.vintage-radio.net/forum/...ad.php?t=42853
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