Old RIFA capacitors and a disaster story - Page 1
Forum section: electronics / general

author: CNe7532294
author_rank: Regular Contributor
timestamp: September 16, 2017, 01:51:20 am
content: Hello everyone,I've seen other forum posts on here and other blogs about this. I've also written some posts about this on the HP/Agilent and R&S yahoo group but I would like to talk about it here too as a reminder. Its a aboutRIFA capacitors.Basically a warning to check for them in older equipment and to replace them on site. It'll be located on the "hot" or "live" side of a power supply board. This needs to be addressed given how everyone nowadays is on ebay buying "reliable test equipment".The story goes that I was using a HP 8561B to see all the types of frequencies used for chatter during Harvey's epic flooding here in Houston. My area became its own island by Sunday morning. On Monday, we were looking for chatter since I had accidentally left my radio equipment at another location or rather I decided to come to a safer location that coincidentally was where we had stored various HP equipment since its higher off the ground and never floods. Prior to the flooding, this unit was kept in a garage that could have been exposed to both heat and humidity. Prior to storage I used the unit for 2 years with no problems. It never got wet and fortunately water did not get inside the house. I took the unit to a room on the second floor. Alot of things went on the 2nd floor like the outdoor grill to the balcony, food to the minibar fridge, important document, etc.I started to test the unit in the computer room on a strong fold up table with fire extinguisher near by in the room. I turned it on for a good 15 minutes to make sure everything was working. Had to check if the crystal was on frequency and everything was good. I turned off the unit and left it plugged in. While texting on a message board to 2 people in the area, I heard a crackle and then a large pop. Confused for a second I thought I left the unit on but the CRT didn't display anything. I immediately raced to the floor to unplug the unit from the wall. When I realized that I never left it on I got a nice whiff of RIFA's magic smoke. I knew this unit was older and it clicked that it might have the same caps I had replaced from our Tek 2467B. Even though that happened I press on to using the "newer" 8563E. Later on confirmed that this unit had newer caps in it and if that failed I had a 8563EC I could part out (damaged RYTHM unit). A few days after when the waters receded and things were settling down I found the time to open the unit.On the time that I needed to use this the most and least expected it this happened is what happened.Bingo. Same caps from the Tek 2467B. Both units made around 87 or 88. Currently right now its just sitting in a corner as is till I had gotten my order and when I find time. A previous order placed on Aug 23rd on Mouser in Dallas could not come till 9/8 due to the damage Harvey had caused to travel. An airport's runaways (KHOU) were completely flooded out and the other airport (KIAH) was used as foward ops base for relief while its surrounding roads were flooded. All vital roads (like I-10) going into the city were blocked by water.The takeaway message here is to, as mentioned above,check and replace all RIFA capacitors. Especially found on units from the late 80s and early 90s. These things crack from thermal stress and aging. This can help the cap blow the magic smoke even while plugged in and the unit is turned off.Questions I have are this:Does humidity play a factor into this? I'm thinking water vapor seeps into the cracks and disturbs whats inside to create a short from live to neutral. I've seen other forums but its generally inconclusive so far.What were the designers thinking? This is just pure evil. They do claim that the caps are self extinguishing and therefore fire proof but I'd rather not test that along with the other surrounding components on the board. All the goo from that sprayed all over the surrounding parts.Anything better? Currently, in a rush, I ordered basically the same thing from Kemet but it seems they changed the encapsulation. It went from yellow to clear gray. The caps on the 8563E/EC are also this grayish color.Any other equipment besides the HP 8561B and Tek 2467B? Feel free to make a list. It'll definitely help.Discuss safety measures? Normally I use a surge protector with a switch or a wall outlet connected to a power switch, even though I instinctively dove down to rip the power cord from the wall socket.

author: tautech
author_rank: Super Contributor
timestamp: September 16, 2017, 04:42:53 am
content: Quote from: CNe7532294 on September 16, 2017, 01:51:20 amSome.QuoteOr the reverse....the electrolyte escapes.QuoteYou are in no way the first or the last that will experience this.QuoteWhat you've ordered will be better due to the better enclosure, remember the enclosure fails not the potting.QuoteMost everything that used RIFA caps from years ago.....how how large do you want to make this list ?QuoteSome maintain there is less risk by leaving equipment powered and I'm inclined to agree but you still have this ticking timebomb waiting for the most inconvenient moment to spill its guts.IME equipment that has been/sat unused for some time is at the greatest risk of RIFA kaboom.

author: Ian.M
author_rank: Super Contributor
timestamp: September 16, 2017, 05:31:09 am
content: Its far from being a disaster - no board damage and when the large one puked its guts it didn't cause extensive contamination. You got lucky.Replacement of all old film caps potted in that sort of clear to amber coloured resin in any high voltage circuit is the ONLY remedy.

author: CNe7532294
author_rank: Regular Contributor
timestamp: September 16, 2017, 06:45:53 am
content: Quote from: tautech on September 16, 2017, 04:42:53 amSeems that way.QuoteNever thought about it that way. Interesting. Does air have a reaction though?QuoteTrue. Thats the unfortunate thing.QuoteAwesome.QuoteWell the point is to raise awareness. The list is up to everyone here. I can contribute by saying a HP 8561B and Tek 2467B (and maybe 2465B with the crt being the only difference) are on this list.QuoteThis is the thing and more. I turned off the unit but as long as its plugged into the mains this will still happen. You've gotta use an external switch to power completely off if just testing for one time use.Quote from: Ian.M on September 16, 2017, 05:31:09 amThe disaster was in reference to Hurricane Harvey here but ya I did get lucky or the unit would have been another disaster. I was distracted and at the time I thought about walking out getting a snack and checking on the rain. Plus I had been awake for an entire day at that point. How can one sleep at all during a hurricane while having access to weather radar showing bleeding red patches of training heavy rain?Right as I got up from my chair it happened. Me acting quickly despite my 3-5 second delay prevented possibly more damage. Pulling the cord part was comical in hindsight though. I had other stuff plugged in that I unplugged as well which was unnecessary as I had an external switch. Stuff like a laptop that was backing up data I didn't want to lose. Thank goodness my usually dead battery was charged on that and I had it plugged in. I usually take it out because sometimes the battery trips the low battery "warning" even when charged.

author: innkeeper
author_rank: Unknown
timestamp: September 16, 2017, 06:52:22 am
content: now i gotta take my hp 8560A apart... well might give me an excuse to replace that fading CRT that i've had the replacement for on the shelf for months while i am at it..

author: bd139
author_rank: Super Contributor
timestamp: September 16, 2017, 08:15:55 am
content: I hate RIFA X class capacitor. I've had them blow up on me numerous times. You are lucky. They can spit fire and cause wanton destruction.

author: medical-nerd
author_rank: Regular Contributor
timestamp: September 16, 2017, 08:50:31 am
content: HiyaI had these blow in two Philips oscilloscopes : PM3055, PM3065 within 20 minutes of each other.Unfortunately the missus was present and it did not endear her to the hobby as I was vigorously waving away the very thick black smoke these beasties produce - it didn't help matters that my lab is in the house attic.At least it wasn't as noisy as a tantalum cap exploding in 80's test equipment - that scared me!Cheers

author: Towger
author_rank: Super Contributor
timestamp: September 16, 2017, 09:01:12 am
content: I sent some NOS ones to Dave for EEVSmoke a while back. He open the envelope in one of the mail bags, but they have not featured releasing their magic yet.https://youtu.be/5SFnZIZa_ZI?t=18m54s

author: Kleinstein
author_rank: Super Contributor
timestamp: September 16, 2017, 10:11:05 am
content: The X class caps do fail sometimes. There are different paths to failure. With these old RIFA ones the usual story is that the case cracks. When turned off for some time humidity comes in, and when turned on again, it can fail with more or less amounts of smoke and fire. The good thing it that they usually fail rather shortly after turned on - so chances are someone is around to notice the smoke.Normally call X2 caps should be used only behind the switch. So it should not happen with a device turned off, but just plugged in. AFAIK (at least in Europe) caps that are before the switch must be class X1 and thus a little more reliable.Another type of failure is less spectacular: here it is just the capacitance going down over time. If used for EMC reasons it usually gets unnoticed. In capacitor dropper type supplies, the lower capacitance at some point is no more enough to operate the circuit and failures start. In some cases higher humidity also seems to speed up this type of aging.It is not only RIFA caps that fail - other caps fail too.

author: Gyro
author_rank: Super Contributor
timestamp: September 16, 2017, 12:10:14 pm
content: Quote from: CNe7532294 on September 16, 2017, 01:51:20 amI think the difference is that [EDIT: those] Rifa caps are Metalized Paper, not MKP or similar. Once the encapsualtion cracks, this is going to make them much more moisture sensitive than plastic film types.The same situation occurs with paper insulated underground supply cables, the wound paper provides excellent insulation until a crack develops in the outer metal sheath (ground movement or mishandling during instalation). Then the clock starts ticking, failure is inevitable. I live in a street with paper insulated mains cable - and an awful lot of patches in the pavement!

author: SeanB
author_rank: Super Contributor
timestamp: September 16, 2017, 04:45:50 pm
content: At least the paper insulated cables are also oil impregnated, so the failures take longer to occur often you find the outer steel tape sheath is completely rusted away, leaving the bare paper sleeving sitting in the red rust remains, and the black tar coat still somewhat present. They generally fail because somebody disturbed them digging to fix another fault. Fun is the old phone wiring, which is not oil impregnated, and where you can burn back an impressive distance when it gets moisture in there, which is not helped by having run ISDN or other multiplexing in the cable, as those use a line supply of 200 to 250VDC to provide power for the far end electronics. Typically in any junction box those pairs are identified by a different colour jumper wire, so that a technician does not plug in a test butt to check for dial tone or apply a tone generator to it, they do not like having 250V applied to them.

author: Gyro
author_rank: Super Contributor
timestamp: September 16, 2017, 05:28:31 pm
content: Ours are aluminuim (Neutral) covered three phase and were apparently bent too tightly during laying. I had the cut off end fromoneof the failures outside my house for a while, it had a very impressive melted stalactite down the side. Too 'messy' to hold onto long term! The clock can tick for quite a few (15-20) years.

author: Nauris
author_rank: Regular Contributor
timestamp: September 16, 2017, 07:25:55 pm
content: That kind of Rifa capacitors used to be used in a lot of fluorescent fixtures. If you look in most often all that remains is a black spot and two leads sticking in the terminal block. That must be the most useless and annoying component ever created.

author: Assafl
author_rank: Frequent Contributor
timestamp: September 16, 2017, 07:49:52 pm
content: Annoying little things. I should figure out if I have any...I always wonder - at what age should we recap equipment? All the capacitors? Just the electrolytic caps (and X1 X2 caps)? My current hypothesis is that the urgency in replacing a cap really depends on their size. Small caps can do little damage whereas large electrolytic caps (or large filter caps) can do a great deal of damage.An example for large scale devastation I had a 15,000uF Cornell Dubillier that exploded in a 5 channel amplifier. The vent is at the bottom so the electrolyte burnt through the PCB, destroyed the transformer and many semiconductors. I opened the other channels and all the same capacitors were beginning to swell. The manufacturer sent a box full of replacement capacitors and a replacement channel.

author: CNe7532294
author_rank: Regular Contributor
timestamp: September 17, 2017, 01:38:16 am
content: This guy covers the warning pretty well. This extends to more than just test equipment as seen on the video.The takeaway being that this can occur powered off and plugged in. I too would like Dave to cover this topic though. Alot of us have bought things from ebay in all sorts of conditions. This could be a majorly bad trap for new players looking for a good score for sure. The more time goes on the more likely we'll see more cases like these. For now I recommend this to be a good safety video for anyone.@AssaflWhat a mess.@NaurisInteresting. All in all people replace lights fixtures more often don't they? Or it seems that something, be it this or something else, would warrent a change.@Gyro"very impressive melted stalactite down the side.""Rifa caps are Metalized Paper, not MKP or similar. Once the encapsualtion cracks, this is going to make them much more moisture sensitive than plastic film types." This I definitely keep hearing or seeing alot.@SeanBI've heard from other places across the pond that these caps burn out faster due to 230V. The rating on my old caps are 250V ordered 300V even though 275V is available.@KleinsteinQuoteAgreed with this. Caps in general are an issue and it further becomes a priority to replace the older they get. Other problems in general like actual leaks to dc leakage.@TowngerQuoteI would like to see this reviewed too and feel like sending in my own caps. As mentioned it would make a good safety video for those getting into electronics and gaining a nice test equipment score.@medical-nerdlol I could imagine the freakout. I had a similar story but mines is a bit unfortunate (noone got physically hurt though) and occurred when I was much much younger. Long story short I'm a hobbist instead of an EE. Told myself for some years I would never touch electronics yet here I am@bd139Agreed. They're evil they must go. In fact I think I'll blow them up or pull a AvE/Widlarize on them.@innkeeperYes, please do. Its a huge favor to yourself.