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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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13th Apr 2018, 9:25 am | #21 |
Heptode
Join Date: Feb 2010
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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.
Stuart |
13th Apr 2018, 10:12 am | #22 | |
Nonode
Join Date: Mar 2013
Location: Leicester, UK
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Re: What to replace a RIFA X2 with?
Quote:
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. Last edited by WaveyDipole; 13th Apr 2018 at 10:20 am. |
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13th Apr 2018, 2:46 pm | #23 | |
Dekatron
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Re: What to replace a RIFA X2 with?
Quote:
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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14th Apr 2018, 8:18 pm | #24 | |
Dekatron
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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:
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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16th Apr 2018, 9:16 pm | #25 |
Dekatron
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Re: What to replace a RIFA X2 with?
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Al |
23rd May 2018, 2:36 pm | #26 |
Nonode
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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. |
26th May 2018, 12:10 am | #27 |
Dekatron
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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. |
26th May 2018, 3:19 am | #28 |
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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. |
26th May 2018, 4:17 am | #29 |
Dekatron
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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. |
26th May 2018, 1:45 pm | #30 |
Nonode
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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. |
26th May 2018, 2:52 pm | #31 |
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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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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
27th May 2018, 12:16 pm | #32 | |
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Re: What to replace a RIFA X2 with?
Quote:
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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27th May 2018, 12:22 pm | #33 | |
Dekatron
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Re: What to replace a RIFA X2 with?
Quote:
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27th May 2018, 12:46 pm | #34 |
Dekatron
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Re: What to replace a RIFA X2 with?
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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A digital radio is the latest thing, but a vintage wireless is forever.. |
27th May 2018, 1:37 pm | #35 | |
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Re: What to replace a RIFA X2 with?
Quote:
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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27th May 2018, 2:36 pm | #36 |
Dekatron
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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. |
27th May 2018, 2:44 pm | #37 |
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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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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
27th May 2018, 2:53 pm | #38 | |
Octode
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Re: What to replace a RIFA X2 with?
Quote:
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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Chris Last edited by evingar; 27th May 2018 at 3:19 pm. |
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27th May 2018, 3:00 pm | #39 |
Dekatron
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Re: What to replace a RIFA X2 with?
RS Pro electrolytics are lowest bidder jobs. Horrid things.
Panasonic, EPCOS, rubycon, Vishay for me. |
27th May 2018, 4:41 pm | #40 | |
Dekatron
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Re: What to replace a RIFA X2 with?
Quote:
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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