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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 13th Apr 2018, 9:25 am   #21
stuarth
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Default Re: What to replace a RIFA X2 with?

I think they add a bit of aluminium “brightness” to offset the dulling you get from suffocating copper in the oxygen free cables.

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Old 13th Apr 2018, 10:12 am   #22
WaveyDipole
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Default Re: What to replace a RIFA X2 with?

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Originally Posted by Diabolical Artificer View Post
Anyhoo, this is off topic. I wonder why the kit put togetherer's used them in the first place, it's not as if they're that much cheaper than an equivalent with a better rep.
Yes, I did wonder that and was tempted to drop him a polite note. The kit came as a 'freebie' when I purchased an expansion ROM/RAM board from a Retro computing enthusiast niche supplier. All it consists of is 4 caps (2 RIFAs, 2 Alu electrolytics), 3 short pieces of heat shrink tubing, a mains cable exit gland and a number of cable ties. Apparently the kit is cheap enough compared to the cost of postage that the seller has offered to throw one in as a freebie on request. The kit does serve its purpose and the extra bits are perhaps thoughtful as one naturally might want to consider replacing the aging mains cable while working on the PSU. Since he had done me a favour (in addition to providing the freebie kit), I didn't want to sound ungrateful or complaining, so I have left it at that. However, being aware of previous discussions on this board, I felt it reasonable to take the precaution of asking for advice before fitting these types of RIFA caps.

I note a couple of reassuring comments about the Suntan, so thanks for that. This is not for a paid for repair - the computer is my own, but I will probably still use a Panasonic in this PSU as I already have one to hand, but keep the Suntan for another less critical use.

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Old 13th Apr 2018, 2:46 pm   #23
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Default Re: What to replace a RIFA X2 with?

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You have a point Al, I was a bit surprised at the strength of feeling behind your point though and the fact you havn't mentioned it before on the "Smoking Rifa's" thread. I was just giving you a bit of friendly gyp BTW, so no hard feelings : )
Hey Andy, cheers! I didn't take it personally, and I don't mind what people choose to do.

I was just trying to point out that a product doesn't define a whole company - not for me, anyway. I think I sounded firm on my line as when I see beginners on threads adopting the assumption that all types of cap from mfr x are bad, I feel that's misleading. I was kind of trained to make a point forcefully for a living, so sometimes I forget to tone it down when it's not so critical.

Anyways, we all get on wonderfully here and perhaps it's time to move on from this focus.

How are you doing? Drop me a PM if you like, I'd like to find out how your latest mega amp is going.
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Old 14th Apr 2018, 8:18 pm   #24
Maarten
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Default Re: What to replace a RIFA X2 with?

@Al: I think your point is valid as well. For example I still buy Wima, the treshold for my above rationalisation is somewhere in between Wima and Rifa and I can fully see why it lies elsewhere for other people.

In general about Suntan: That brand has been around for some time, lots of Hong Kong transistor radios used them.

Quote:
Originally Posted by Diabolical Artificer View Post
https://www.hificollective.co.uk/components/evox-rifa-capacitors.html[/url] , maybe they were included for their tonal qualities? Might be an idea to hold on to your old RIFA's, might be worth a bob or two in a few years.

Lastly on the main product page - https://www.hificollective.co.uk/com...a-pme271m.html it says this - " Evox Rifa are the last remaining manufacture of metallized paper capacitors." This may be indicative.
I've always thought they looked pretty on a circuit board, for example in Swedish Philips TV sets. I'm a visual kind of guy, maybe they sound good for the more auditive minded I've got a bag of cracked new old stock ones, I'll hang onto them.

I'm not sure where the claim about being the last manufacturer comes from. Wima still makes them, I verified on their website. Maybe I'll shoot them a mail asking why I would choose one of those in stead of the MKP type they market alongside. I expect a more honest answer from them than from "Rifa".

Last edited by Maarten; 14th Apr 2018 at 8:26 pm.
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Old 16th Apr 2018, 9:16 pm   #25
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Default Re: What to replace a RIFA X2 with?

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@Al: I think your point is valid as well.
Thank you ,Maarten!
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Old 23rd May 2018, 2:36 pm   #26
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Default Re: What to replace a RIFA X2 with?

I have just got around to pulling the PSU from the computer and it looks pretty clean. However, there are far more electrolytic caps present than the 2 x electrolytic caps supplied with the "capacitor replacement kit". I can see one that corresponds (220uF at 35v), but I can't see anything to correspond to the supplied Suntan (220uF at 50v). Most of the caps look OK with no indication of leaking. They are a mixture of Nippon Chem Com and Marcon. I don't recognize the latter although I think I have seen the former. One cap with a top that is starting to bulge, so this will have to be replaced. I am wondering whether to replace the others while I have the PSU on the bench?

Soldering looks to be original although one securing screw is probably halfway undone.

On reflection, I think I will use the two RIFA caps I was supplied with. The originals have lasted a few years and I see no obvious signs of cracking or damage so I guess the new ones should also be good for a few years.
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Old 26th May 2018, 12:10 am   #27
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Default Re: What to replace a RIFA X2 with?

Please check the date codes on the supplied RIFA's before doing that (and regardless, don't do it anyway, it is in general quite a bad idea to replace safety components by known dubious ones).

Reason for checking the date codes is of course that they age in stock as well.
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Old 26th May 2018, 3:19 am   #28
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Default Re: What to replace a RIFA X2 with?

The question what to replace them with I think is fairly simple. Simply avoid X2 capacitors that are constructed from metalized paper. As long as they are some type of other poly cap, like MKP etc they will be just fine and if you get the ones that are "X2" rated, you know they are compliant with modern safety standards.

However, it might be easy to forget, before these standards specifying the X2 capacitor existed, manufacturers who wanted to put mains suppression capacitors on the mains power inputs to their radios & TV's etc, just used standard parts, either oil filled, mica or ceramic types, even seen waxies. But what they did was use 1000v or 1500v parts and so, they practically never failed.

You could expect a modern 240V AC rated X2 cap only to be good for very roughly 600V DC, but certainly not 900V. I think 1kV DC rated caps, or higher, are better for mains RFI filters.

The main problem is they made many X2 caps too compact so the insulation is just too thin for voltage spikes that ride on the mains and the insulation gets damaged by them. Better thicker insulation makes the capacitor bigger. But that is the price to pay for reliability in the application.

So I'm much more confident with a 1kV+ rated MKP or other poly cap as an RFI filter device on mains, than a metalized paper official X2 type whose uF value is constantly falling with time and is waiting to smoke. 1200V rated caps are a very good option for size & value and reliability. As noted on another thread, the 1500V rated tuning capacitors for transistorized line output stages make a far superior mains RF filter cap as they also have a very low ESR and welded internal construction.

Of course, ideally, there is always a fuse between the mains input and the RFI filter so the current is limited if the capacitor shorts outs, but sometimes you will see the RFI filters built into IEC connectors with no fuse and I don't think that is a wonderful idea, but at least they are enclosed in a metal shell that mitigates the fire risk.

Last edited by Argus25; 26th May 2018 at 3:29 am.
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Old 26th May 2018, 4:17 am   #29
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Default Re: What to replace a RIFA X2 with?

I have had a Rifa go off in a vacuum cleaner and it never melted the surrounding plastic even though it was live side of the mains switch and carried on after switching off.
I used a 1700V fly-back capacitor and tested it against a LW radio and it was fine. The value was 6n2.
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Old 26th May 2018, 1:45 pm   #30
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Default Re: What to replace a RIFA X2 with?

Hmm, I did wonder whether 1kv or higher ceramic caps might be suitable as they often appear as filter caps on the mains input.

It does look like my observations earlier were premature. I have now managed to get the PCB out of its case and can clearly see the underside. The two RIFA's along with the first Rubycon electrolytic cap are already replacements, which correspond to the 'capacitor replacement kit'. The remainder of the PSU looks untouched.

I am genuinely puzzled by the 'capacitor replacement kit' as this PSU has some 10 aluminium electrolytics, but only one (possibly for the oscillator circuit) is supplied along with the two RIFAs. Replacement for the two 250v caps across the rectifier DC output or the smoothing caps across the low voltage DC outputs are not provided or even mentioned as being required. In my unit, one of the 1000uF DC output caps was bulging badly and once removed showed evidence of leaking electrolyte. I replaced all 3 1000u and the two 100u but didn't have the 2200uF to hand.

Why would a replacement kit offer only 1 replacement cap out of the 10 that are present in the unit? I appreciate that the cost would be higher and I don't necessarily agree with blanket replacement, but on a 30 year old SMPSU, since I have already gone to the trouble of removing it and extracting the board I think I would rather play it safe and do just that while I am working on it.
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Old 26th May 2018, 2:52 pm   #31
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Default Re: What to replace a RIFA X2 with?

I've only ever repaired two PSU supplies and in both cases it was the cap associated with supplying power to USB devices which had failed.
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Old 27th May 2018, 12:16 pm   #32
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Default Re: What to replace a RIFA X2 with?

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Why would a replacement kit offer only 1 replacement cap out of the 10 that are present in the unit?
So whoever assembled the kit doesn't realize in a supply of this age, all the electros require replacing.

I'm afraid that the only way to properly re-cap a vintage switch-mode psu is to take note and document every single electrolytic in it from the supply itself & the schematic, uF capacity and voltage and physical geometry height and diameter where important and radial lead spacing, then sitting down with something like the RS or Farnell/Element 14 catalog, patiently selecting suitable 105 deg C rated replacements, preferably items like Panasonic or Nichicon brand low ESR types (designed for SMPS use), and replace the X2's while you are at it.

If you buy a "kit" somebody else has assembled, you are only likely to get part of what you really need and there is no guarantee of the origin/quality of the replacement caps. Likely they will be the cheapest option, which is exactly what you do not want for a SMPS. So you have to take on the task of assembling your own capacitor kit for the job yourself and not rely on another party, or these are the kind of disappointments that wait in the wings. You are not alone, I have been through this myself. I once bought an expensive capacitor kit for a valve amp refurbishment, many were not suitable, missing and wrong values and poor parts, I only used about 10% of them in the end.

Last edited by Argus25; 27th May 2018 at 12:30 pm.
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Old 27th May 2018, 12:22 pm   #33
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Default Re: What to replace a RIFA X2 with?

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Originally Posted by WaveyDipole View Post

Why would a replacement kit offer only 1 replacement cap out of the 10 that are present in the unit? I appreciate that the cost would be higher and I don't necessarily agree with blanket replacement, but on a 30 year old SMPSU, since I have already gone to the trouble of removing it and extracting the board I think I would rather play it safe and do just that while I am working on it.
One possible reason it that, when the replacement kit was first thought out, maybe even 20 years ago?, it was probably just that 1 electrolytic causing regular problems.
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Old 27th May 2018, 12:46 pm   #34
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Default Re: What to replace a RIFA X2 with?

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To be honest RIFA caps are absolutely fine as long as you replace them every few years.
In the words of one John McEnroe, you can't be serious? Personally I would never fit any component that I knew I'd have to change in a few years time. Given the amount of sets old and new that I have it's bad enough trying to keep up with 'normal failures' and 'get-around-tuit' restorations without fitting components that I know are unreliable and likely to fail.
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Old 27th May 2018, 1:37 pm   #35
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Default Re: What to replace a RIFA X2 with?

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In the words of one John McEnroe, you can't be serious? Personally I would never fit any component that I knew I'd have to change in a few years time.
I agree with you on this totally. Especially with the amount of time and work required to restore a vintage set of any kind, I go for the highest quality parts and as I noted on other threads I try to eliminate electro's where possible in valve gear now, because I don't want to have to go back in later for repairs. And this applies to the X2's also.

In transistor/IC gear I use the highest quality highest temperature electrolytics available with the longest hrs rated life. While the better electros might cost a few extra $ in the short term and you have to order them and wait to get them, in the long run it is worth it and if some fault does develop later you don't have to immediately start questioning the electrolytic caps.

One thing in SMPS's often the designers place many of the electros close to heat sinks. These are always the ones that dry out and go dome topped with gas pressure first. So there could be an argument for selective replacement.

But if the SMPS is 30 or more years old (especially in SMPS where ripple currents are high) and some of the caps are already "expired" I think if you want a reliable supply after your refurbishment, it is better to replace every electrolytic. Or likely, after a while, you will be finding your way back in there for repairs. And its logical to do it the first time, when the supply is undergoing repairs, not having to reinvent the wheel and go back in later. So there is really no logic in leaving any of the old electrolytics in there and replacing just a few in an old SMPS where some failed in the first place.
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Old 27th May 2018, 2:36 pm   #36
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Default Re: What to replace a RIFA X2 with?

Everything has a design lifetime. Planning that is part of engineering.

The job these capacitors do is a sacrificial one and basically to break down on any transients. The lifetime is a function of the transients.

Arguably this isn’t even a trade off between cost and lifetime. All the plastic replacements are unknown at this point. After 25 years, do we really know what will happen to suntan X2’s? Nope!

What we do is plan for failure rather than attempt entirely to prevent it. Service your equipment every decade and factor that into the cost of maintaining it. Service means replacement much like seals and fluids in a car.

When we own or repair “vintage” gear we’re extending the life of things the manufacturer thought would have been tossed by now.
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Old 27th May 2018, 2:44 pm   #37
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Default Re: What to replace a RIFA X2 with?

Before I knew better I used to replace waxies connected across the mains with 1000V polypropylene types. I've never gone back to change them for Class X types and none have ever failed.
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Old 27th May 2018, 2:53 pm   #38
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Default Re: What to replace a RIFA X2 with?

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Suntan are supplied by Conrad/Rapid. They do a wide range of 105deg low impedance electrolytics and various other bits.
I haven't had a problem either but I would rather use something more upmarket for a paid job.

Indeed, the impression that's given is of "Nickle and Diming" fitting any of these slightly usual brands. I generally use Panasonic or Nichicon types.


I did dabble with the RS own brand stuff - but had an in warranty "bounce" (went High ESR) so now avoid.
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Old 27th May 2018, 3:00 pm   #39
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Default Re: What to replace a RIFA X2 with?

RS Pro electrolytics are lowest bidder jobs. Horrid things.

Panasonic, EPCOS, rubycon, Vishay for me.
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Old 27th May 2018, 4:41 pm   #40
Maarten
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Default Re: What to replace a RIFA X2 with?

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Originally Posted by MrBungle View Post
Everything has a design lifetime. Planning that is part of engineering.

The job these capacitors do is a sacrificial one and basically to break down on any transients. The lifetime is a function of the transients.

Arguably this isn’t even a trade off between cost and lifetime. All the plastic replacements are unknown at this point. After 25 years, do we really know what will happen to suntan X2’s? Nope!
While I do to some degree agree that X2 capacitors break down at transients, that is not the normal mode of operation only the normal mode of failure. A cheap polyester one is more likely to exhibit failure than a polypropylene from a more reputable brand. As Station X says, a non-X2 polyprpylene of a sufficient rating just won't fail (but has a minor chance it will fail a bit more destructive if it ever fails).

That said, while we don't know how the Suntans will hold up in 25 years, we DO know that the RIFAs are already defective (not by breaking down at transients but by other failure modes) at the very moment when we mount them so it's probably best to skip that step altogether and bin them.
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