Failing RIFA Safety Capacitors!
ฝัง
- เผยแพร่เมื่อ 6 ก.ค. 2024
- In this video I'll explain the details about safety capacitors, what are they, how they are used, X and Y class ratings, and why older RIFA safety capacitors need to be replaced. How to solder and desoldering tips are shown too.
#capacitor #learnelectronics #electronicsrepair - วิทยาศาสตร์และเทคโนโลยี
![[LIVE] : ONE ลุมพินี 69 | คู่เอก "กุหลาบดำ vs นาบิล"](http://i.ytimg.com/vi/PNM6U8e_HMo/mqdefault.jpg)
I watch a lot of videos about older electronics, and they often mention RIFA caps in passing but don't elaborate. This was the perfect explanation. Thank you!
Glad to know you found the video helpful, thanks for watching!
This is the best explanation of safety capacitors that I have seen. Thanks!!
Thanks for the nice compliment!!
There is no safety involved with these capacitors. They are used to suppress line and SMPS noise. The usual arrangement uses 3 devices, one between the Active and Neutral being around 0.1 uF in conjunction with two others of about 0.002uF wired from the Earth to Active and Neutral respectively. The 0.1uF 250ac device has proven to be most problematic. I had two pieces of HP8563E gear go up in smoke minutes of plugging the equipment into the mains. Have spent their life on 120Vac mains and then being exposed to the 240Vac has resulted in rapid destruction. I replaced them with an ac rated mains capacitors of 275Vac and never had any further trouble. But the word Safety should never be in the same sentence as these type of capacitors.
The term "safety capacitor" is in fact what the devices are called. They are also called X class and Y class capacitors. If you watch the video I address the fact that the term "safety" is related to the capacitor's internal design and how they are suppose to fail. I also discuss how and why they are used. The old RIFA types have aged poorly and are anything but safe now.
Fantastic explanation. Thanks
A good, clear description of what the device is supposed to do, its limitations, and what problem exists with it. I just found your channel in the last few days and I like the subjects and the way you present the material. As a suggestion, you might discuss sources where hard to find parts (like RIFA Safety Caps) can be purchased. Excellent either way !!!
Thanks for the compliments! Glad you enjoy this channel. I'll try to include parts sources on future videos, I agree that would be helpful. The RIFA capacitors are available at Digi-Key.
Dave @ EEvblog recently did a video on "Safety Caps" , that, although did not have outward signs of physical damage, but one was used as a voltage dropper to power a low voltage linear DC power supply section of a heater ( "overseas designed") that had failed and caused the control panel on a space heater to quit functioning. After "de-potting" the failed cap, and unwinding the foil, you could see visible signs of internal damage,or, how the capacitor foil was designed to pretty much vaporize at a weak point where the stress of a surge made continuity. Over time, the cap wouldn't short circuit, but it would slowly be out of tolerance as far as capacatance value is concerned. I would probably put these types of components on a list for replacement as far as a maintenance visit inside of an assembly goes, unless you tested them for proper value to tolerance and leakage before calling it good.
Another excellent video, Thanks for sharing Erik. 🎅🎅
Glad you enjoyed the video, thanks for watching!
Great video, just one remark: Y-capacitors are often even more safety critical than you described. Nearly every class-II SMPS uses Y-capacitors between the primary and secondary side of the transformer to surpress EMI. If a Y-capacitor fails in a class-I device - like you have shown in your sketch - then usually the failure current is going through PE and the RCI or even the circuit breaker trips. But if a Y-capacitor in a class-II device fails, then you have mains voltage directly on an output that usually is not earthed - e.g. on the output of your smartphone charger. An electric shock is more or less unavoidable in that case.
Thanks for watching. The Y class capacitor is supposed to fail to an open circuit for protection but of course these RIFA caps fail in the worst possible way. There is a good article on class-I and II power supply differences here www.emea.lambda.tdk.com/il/KB/What-is-the-difference-between-Class-I-and-Class-II-power-supplies.pdf
@@EriksElectronicsWorkbenchThanks a lot for the Appnote - it really is a great resource of knowledge!
What I wanted to say is that the more expensive class-I devices generally have branded and (except maybe the old RIFAs) high-quality Y-caps, though their shorting mostly only leads to a tripped breaker.
The tons of dirt-cheap consumer SMPS, like chargers or other wall warts, directly endanger the life of the user. That's why, in my opinion, if we talk about dangerous Y-caps, we should never forget the class-II devices.
Good explanation, nice work.
Thanks for the compliment, glad you enjoyed the video.
Nice informative video!
thank you!
Nice Video, When you refer to 240V it would be nice if USA-specific issues were pointed out. UK has 240 V and we have Live, Neutral and Earth ( chassis) this two-line thing is new to me. Now all I have to do is find a supplier for my VCR safety cap. Cheers.
Your point about 240 volt power distribution in the USA vs. other countries is noted. If you are looking for electronic components in the UK you may find the list here helpful www.icrfq.net/electronic-components-suppliers-in-uk/
@@EriksElectronicsWorkbench Thank you. Merry Christmas.
Nice informative video.👍 What model is that desoldering tool you use? It seems to work well.
Glad you found the video helpful. The desoldering tool is Hakko FR-301. I would definitely recommend it. link to manufacture's webpage.. hakkousa.com/fr-301-portable-desoldering-tool.html
i can be wrong, but in my opinion, Rifa caps start to acttract moisture arround the leads, and once the moisture gets inside, they start to swell, and that swelling cause the cracks in the housing. i experienced many times a bad Rifa cap, and each time when they where cracked, they where also bulged. Never seen a Rifa cap with only cracks without swelling.
A few years ago, i bought some high voltage Electrophoresis powersupplies trough Ebay from USA sellers, where they previous where used on 110/120V, the first time when i received such a powersupply, i opened the powersupply and everything look fine, set the voltage select switch to 230V and power up the powersupply, and after a few seconds, the Rifa cap bursted open in flames.
The entire room smelled for days like burned wood. That Rifa cap was rated for 250V, for use in the USA with 120V, thats fine, but for use here in Belgium or Europe with 230/240V, that is not enough extra headroom. Since that day, i replace every Rifa cap with a Kemet or Wima cap, and choose for a 310V or 400V rating.
Hi, yes I agree they could be cracking around the leads. However I have seen them with cracks in the case and no swelling and then some with swelling, and yes when they let out the smoke the whole room smells!! I had a Tektronix scope with a failed RIFA that set off the smoke alarms.
@@EriksElectronicsWorkbench , i don't trust a Rifa cap,even the new ones. Never seen other brands burst open like that, even the yellow ones in cheap electronic devices like floodlights with motion sensors etc.....
@@BjornV78 I have installed the new production RIFA and not had any issues with them but of course there are other brands and I do use them as well. Yes the problem seems to be with the older original version RIFA and agree other brands did not appear to have the failure problem.
Same here in Australia. HP test equipment from Japan and Korea went up in smoke within minutes on 240Vac.
250V peak isn't nearly high enough headroom for 230VAC (RMS)! For example, surge protection varistors should be 470V!
7:34 "What the manufacturer did not assume was going to happen"
would you tell where we can buy relaiable safety caps? I know the mouser but other than that...
DigiKey is my other go to besides Mouser.
I suspect a failed Dain capacitor is the reason the rv fireplace board quit working. I tested both ends where its leads were soldered in and no continuity? I've read they are not very good. Any suggestions? Thanks
Capacitors don't have continuity through them so it's normal to show an open on an ohm meter. If you do not like the RIFA brand you can replace it with other manufactures as long as the tech ratings are the same. Mouser and Digikey have many safety capacitors in stock.
Ok, then there is something else wrong with the electric RV fireplace board? Just buying a new fireplace but just curious as to why the board quit working? There is power going into the board but not going out?
👍
Hi there. X capacitors have + and - poles? Thank you
Hi, the X and Y class capacitors are non-polarized. They can be installed in either direction, no worry about + or - polarity.
@@EriksElectronicsWorkbench thank you.
I wondered "Are they still needed these days?" Removed a blown one from my Revox B790, didn't replace it.
Yes they are needed in modern equipment especially with switchmode power supplies to help suppress the interference generated within the power supply. Sometimes older equipment had them just to suppress sparking on the power switch and/or provide some basic RFI suppression from the outside world.
How do these capacitors protect the circuit? From what does it protect the circuit?
The "safety" is intended for the user of the device more than the circuit. The capacitors are generally for RF noise interference suppression, radiated or received, and are across the AC line. They are supposed to fail in a safe way to prevent shock and fire hazards.
@@EriksElectronicsWorkbench but then, from what does it protect the user?
@@gabrielphilips6980 the protection is from electrical shock and fire. Non-safety rated capacitors might fail to a dead short where as a safety capacitor fails to an open circuit. The failure could be initiated by a high voltage surge.
@@EriksElectronicsWorkbench can a safety capacitor protect the circuit from a lightning strike?
@@gabrielphilips6980 safety capacitors are not intended for lightning protection. They offer no protection from large voltage surges. However there are other types of devices for clamping or shunting voltage surges but keep in mind a direct lightning strike is pretty much impossible to offer protection against.
Do you really need to show how to replace a cap ???
I try to make my videos informative for viewers of all skill levels. If you are new to electronics repairs it could be helpful.
Do you really need to post such a stupid comment?