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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 10th May 2011, 9:28 pm   #21
evingar
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Default Re: Beware!

A while ago, I had this type of Rifa fail on an old Philips 'scope - The 'scope was working perfectly well, but started making a "frying" sound. While I was still scratching my head wondering about the noise, smoke poured from every available hole in the chassis. Completely filled the workshop.

IMHO, like bead tantalum caps, best avoided all together in "high energy" positions. I'll be changing any I find on sight from now on.
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Old 12th May 2011, 10:23 am   #22
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Default Re: Beware!

I have had failures of this type of capacitor recently on three different computer power supplies dating from the mid eighties.
They go with a 'crack' and produce lots of smoke but no fuses blow and the equipment keeps running !
I will post some pictures I took when I can find them....
I think these capacitors must have a certain 'shelf life' and possibly not like temperature changes too much judging by the stress cracks I have noticed on their cases.


Andy
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Old 12th May 2011, 10:48 am   #23
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Default Re: Beware!

Hi lads,

I'm pretty sure that these are the ones that live (and die) in BBC Micro PSUs. The first time one went it didn't half make me panic...since then I've had a few go and don't even bother to stop typing. Though it is worth getting up and opening a window!

As far as I know they are "safe" in that I've never seen or heard of one setting fire to adjacent materials.

Dom
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Old 12th May 2011, 11:06 am   #24
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Default Re: Beware!

I've struck blown ones in a Sord M23 power supply and one of my Apple IIe's had so much smelly old capacitor goo through it's power supply I had to wash the PCB in the dishwasher twice to get most of it off! It had two blown - 0.47uF across the mains and 0.1 a little later on in the circuit.

They seem to crack, aborb moisture and fail. I replace them on sight.
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Old 12th May 2011, 12:00 pm   #25
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Default Re: Beware!

Had one fail last year in a Tandberg reel to reel series 15 motor switch. Caught it before the smoke, after noticing a strong smell and the motor randomly coming on. Definitely a type to replace on sight, file under 'old crap'!
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Old 12th May 2011, 12:19 pm   #26
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Default Re: Beware!

Oh well looks conclusive, 250 of them in the bin then
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Old 12th May 2011, 2:28 pm   #27
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Default Re: Beware!

HI: Chris,don't bin them,I must say the we did have some go when the RFI testing station , did on our induction hobs wacked accesive voltage in to our mains input plugs with there testing equipment and blew a couple,we also found that the mains switches where faulty and causing arcing and the caps started to overheat.
Also another problem was the soldered joints on the circuit boards were crap.

After replacing said switches/soldering joints, there were no more problems.
Here are some technical info for you.if you require anymore let me know.Gezza.
Attached Files
File Type: pdf RIFA 1.pdf (1.25 MB, 927 views)
File Type: pdf RIFA 1.2.pdf (1.24 MB, 727 views)
File Type: pdf RIFA 2.pdf (1.08 MB, 541 views)
File Type: pdf RIFA 3.pdf (901.3 KB, 1036 views)
File Type: pdf RIFA 4.pdf (733.6 KB, 948 views)
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Old 12th May 2011, 2:30 pm   #28
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Default Re: Beware!

more, Chris
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File Type: pdf RIFA 5.pdf (775.5 KB, 580 views)
File Type: pdf RIFA 6.pdf (676.0 KB, 375 views)
File Type: pdf RIFA 7.pdf (624.6 KB, 2574 views)
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Old 12th May 2011, 4:45 pm   #29
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Default Re: Beware!

Wow Gezza, some great data and I do love data thanks very much I shall digest.

Chris
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Old 12th May 2011, 6:26 pm   #30
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Default Re: Beware!

Chris!
You should change your log in to Johnny5! Hee Hee
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Old 12th May 2011, 10:05 pm   #31
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Hello Johnny 5. I mean Chris.I will send you the original wall chart to go in your workshop when I'm next at the post Office as I have a spare.Gezza
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Old 12th May 2011, 10:15 pm   #32
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Default Re: Beware!

That's such a kind gesture Gezza and one which is truly appreciated.

Chris
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Old 13th May 2011, 9:22 am   #33
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Default Re: Beware!

I've attached some pictures of these Rifa's from a BBC micro PSU. The first two show the one which blew and the second two are of the 0.1uF which although not blown, was leaky.


Andy
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Old 13th May 2011, 9:37 am   #34
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Default Re: Beware!

I meet up with these little sods in commercial equipment I service. I test them at 1000 volts and if they show any leakage at all, they get changed. If the outer coating shows any crazing they are on the way out so get changed even if they pass the megger test.

Without question, potentially the most unreliable capacitor I have ever seen, apart from Hunts, Wima, TCC and UCC, and at least they had the excuse of being much older technology and made at a time when our expectations were significantly lower.

Cheers

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Old 13th May 2011, 10:16 am   #35
Leon Crampin
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Default Re: Beware!

So, if I found these capacitors to be unfit for the purposes of my employer 30 years ago, how did Rifa manage to obtain all of the international certifications for this component?

It really makes you wonder about the true value of these bureaucratic test houses - I used £30 worth of test equipment and a bunsen burner.

Leon.
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Old 13th May 2011, 11:51 am   #36
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Default Re: Beware!

I heard that the problem of old was that these capacitors were originally specified for US 110V supplies and that when dual voltage supplies started to become more common not everyone uprated them as they looked on paper to be OK. It just meant they had a shorter life when not in the US.

I experienced a definite example of this when the filter in the Apple LISA psu went up as described. It didn't originally have a 240V supply but they upgraded it but was still essentially the same design.
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Old 26th May 2011, 2:08 pm   #37
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Default Re: Beware!

It was my turn last night... I was happily listening to my Revox B77 then suddenly, fizz, pop, BANG. Remarkably the mains fuse remained intact and the recorder kept on playing. As I sat in a smog filled room wondering what had just happened I was aware that couldn't hear the the tape very well due to my smoke alarm making too much noise!

Notice that the cap is also a PME271 M610

p.s. Just how long does it take for that acrid smell to go away??

Vic
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Old 26th May 2011, 5:12 pm   #38
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Default Re: Beware!

Quote:
Originally Posted by Vicboduk View Post
p.s. Just how long does it take for that acrid smell to go away??
Well there were traces of it in my workshop 2 days after the event
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Old 26th May 2011, 7:04 pm   #39
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Default Re: Beware Rifa Class X Capacitors!

About ten years ago, I had the same problem with a Sony colour set manufactured in the mid 1980's (can't remember the chassis). At the time, I was quite alarmed to find an X2 rated component fail in this way considering the stringent safety approvals for this capacitor. I think the set was that nasty one which suffered from a burn up of the main chassis due to dry joints on wirewound resistors.
I have also noticed fine cracks in the case of some Rifa class X2 capacitors so wondered whether moisture could be to blame.

Symon.
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Old 26th May 2011, 7:39 pm   #40
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Default Re: Beware Rifa Class X Capacitors!

That does it! I had a couple of recovered PME271 capacitors in my spares store. They are now heading for landfill.
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