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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 14th May 2024, 3:11 pm   #1
knobtwiddler
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Default RIFA X2 Capacitor in Action!

As is often discussed here, it's best to approach aged capacitors with pragmatism. Simply being old (electrolytic in particular), doesn't mean a cap is bad (some can be decades old and test perfectly). However, there are a couple of notable exceptions, both of which can be seen in the [otherwise great] Studer / Revox ranges: Frako electroytics (pass DC and leak gunk onto the PCB - if they aren't doing it now, they likely will at some point) and RIFA X2 caps. In case you're wondering why members here are keen to suggest replacing the latter on sight, check out this video and see for yourself:

https://www.youtube.com/watch?v=YtGdWZ93-uQ

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Old 14th May 2024, 4:02 pm   #2
bigfathairyvika
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Default Re: RIFA X2 Capacitor in Action!

I've always wondered about RIFA X2 caps being a change on sight, when the new ones look exactly the same.
Would RIFA risk selling dodgy caps even now?
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Old 14th May 2024, 4:19 pm   #3
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Default Re: RIFA X2 Capacitor in Action!

Why did the music stop? It didn't stop when this went in a tuner-amp I'm working on, the 0.µF RIFA just turned itself into a 0.4µF RIFA and carried on working
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Old 14th May 2024, 4:54 pm   #4
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Default Re: RIFA X2 Capacitor in Action!

Are Frakos in the same category? A shame as they look very Germanic, funky (funken?) and purposeful on a circuit board! I have replaced some with Wuerth which have a similar 'period' look to them with their vibrant red colouring, and DIN-ish typeface.
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Old 14th May 2024, 5:09 pm   #5
knobtwiddler
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Default Re: RIFA X2 Capacitor in Action!

I've not seen Frakos in any form other than electrolytic. They have a propensity to leak green gunk that's hard to remove, go way out of tolerance and - unsually for an electrolytic - pass DC. Their failure modes aren't as entertaining or smelly as a RIFA when confronted with 240VAC, though!
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Old 14th May 2024, 5:40 pm   #6
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Default Re: RIFA X2 Capacitor in Action!

Sorry, I meant 'replace on sight' rather than 'paper-dielectric' as the category I was referring to. I'm lucky I've not had any leak then - they're common in Uhers which I have a soft spot for. Some of the equally period-looking hard-cased maroon Roedersteins have failed without any dramatic excitement, necessitating a lot of removing and checking. At least you know where you are with a RIFA BANG.
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Old 14th May 2024, 5:48 pm   #7
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Default Re: RIFA X2 Capacitor in Action!

Some peeing Frakos, these are NOS....

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Old 14th May 2024, 8:26 pm   #8
m0cemdave
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Default Re: RIFA X2 Capacitor in Action!

Those Frako's were also used in B&K test equipment - often left on all day in labs, stacked up against the wall with poor ventilation. In such circumstances it's no surprise that they have exceeded their service lifetime, and I have replaced a lot of them.

I think they were considered to be of high quality in their day but the passing of time has shown them to be much inferior to the blue Philips types, which last a lot longer.

Interesting to see NOS ones failing too, it looks like they have joined the blue Tants as things to evict from the stores on sight!

Last edited by m0cemdave; 14th May 2024 at 8:31 pm.
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Old 14th May 2024, 8:43 pm   #9
paulsherwin
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Default Re: RIFA X2 Capacitor in Action!

To be fair, all these caps are consumer grade with a standard expected 10 year lifespan. We tend to explain them to survive for 50, 60, even 70 years.

The notorious Rifa X2s tend to fail after 20 or 30 years - not great, but not really surprising given the construction.
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Old 15th May 2024, 12:08 am   #10
Maarten
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Default Re: RIFA X2 Capacitor in Action!

Depending on circumstances, especially when stocked unclimatised or used in harsh environments, they can fail much, much earlier. However you're right given normal use, preferrably continuously and/or climatised (stable temperature and low humidity) and under ideal electrical conditions (not self healing too often), they will usually last at least 20 years. Which is not bad relative to the use (even professional equipment isn't expected to last beyond 20 years), but extremely bad compared to the competition - especially given the fire hazard once they begin to expire.

Quote:
Originally Posted by bigfathairyvika View Post
I've always wondered about RIFA X2 caps being a change on sight, when the new ones look exactly the same.
Would RIFA risk selling dodgy caps even now?
Yes, they are selling the same paper crap (possibly the only type approved for some ancient NATO, aerospatial or industrial stock - recertification might cost more than changing out the capacitors periodically); remember that most of them only become dodgy after the warranty expires - and then proceed to burn the place down if you're unlucky but that's not the manufacturers problem anymore. Yes you should change them on sight and no, you should never use paper capacitors of any type (RIFA PME or WIMA MP3) as a replacement. Use an MKP or MKT type instead.

Last edited by Maarten; 15th May 2024 at 12:18 am.
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Old 15th May 2024, 12:48 am   #11
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Default Re: RIFA X2 Capacitor in Action!

I'm impressed that after letting out an alarming sharp 'crack' this one seems to have retained most of its smoke but turned it into free bonus capacitance. I made a typo in my first post, the specified 100nF has been augmented by 330nF or more (it varies every time I measure it). There's still more ohms in there than I can measure
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Old 15th May 2024, 1:34 am   #12
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Default Re: RIFA X2 Capacitor in Action!

Some forum users say that leaking capacitors can confuse capacitance meters and overestimate the actual capacitance.

Could you check your reading by adding a known good capacitor in series with the faulty one?
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Old 15th May 2024, 12:44 pm   #13
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Default Re: RIFA X2 Capacitor in Action!

Thanks but I don't think it's leaking, the DVM can't find any Ohms to measure so I put a 4µ7 polyester in series and the component tester still reports ~400nF
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Old 15th May 2024, 2:29 pm   #14
kalee20
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Default Re: RIFA X2 Capacitor in Action!

I understand the thinking, but it's not DC leakage that is confusing the results.

A capacitor in parallel with a resistor, at any one frequency, can be equally represented as a slightly different value of capacitance in series with a different resistance.

When the parallel resistance is really large, the series capacitance is almost the same value (and the equivalent series resistance is very small). But when the equivalent parallel resistance is lower, the equivalent series capacitance is rather larger, (and the equivalent series resistance also larger). That's what you'll have here.

Binning these horrid Rifa metallised paper capacitors is the only solution!
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Old 15th May 2024, 3:28 pm   #15
factory
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Default Re: RIFA X2 Capacitor in Action!

Quote:
Originally Posted by Maarten View Post
Yes, they are selling the same paper crap (possibly the only type approved for some ancient NATO, aerospatial or industrial stock - recertification might cost more than changing out the capacitors periodically); remember that most of them only become dodgy after the warranty expires - and then proceed to burn the place down if you're unlucky but that's not the manufacturers problem anymore. Yes you should change them on sight and no, you should never use paper capacitors of any type (RIFA PME or WIMA MP3) as a replacement. Use an MKP or MKT type instead.
Actually RIFA Kemet madness has since evolved into surface mount form, no idea why or who wanted them or who thought this was a good idea , I was really hoping metallized paper capacitors would become obsolete.

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Also avoid any Kemet/RIFA part starting with PM or PZ and beware of newer metallized paper based Kemet/Yageo parts that don't start with the old three letter system of RIFA.

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