EEVblog #1183 - RIFA Madness (Schaffner Repair)

hi in the previous video we took a look at the teardown of this Schaffner NSG 200 and NSG triple 2i interference mains interference simulators are very cool and interesting bit of kit so I'll link it in down below if you haven't seen it anyway we thought that there was a failure in the transformer over here but well let's take a closer look now of course when I plug this thing in it took some time but eventually while I was trying to use it release the magic smoke and I thought it was coming around this back area here because the the top part of it just has all grills on it like this so the smoke was sort of coming out of this back region so we're not opened it up and I saw this down here I thought AHA that looks like the culprit this huge common mode choke on here and you can see it does actually look as if like something like has burnt and then melted and dripped down and something like that but as I remarked in that video because this is just a common mode choke I I found it really hard to think of the mechanism that would actually cause it to do that because it's not like you know a transformer anything if one turn just shorts to another so you know it's not really a big deal and anyway so I didn't really investigate it any further so it seemed like that was the culprit but as it turns out one of my viewers actually worked or is still working at a transformer manufacturing company he said no this is actually quite common it just looks like the residue from the polly put the kettle on coding that they actually apply to this thing and it's no big deal like that is not a burn mark at all and upon closer inspection I am pretty darn sure he's right because look it looks like it's sort of like dripped out of there like that so yeah I don't reckon I think now I'm pretty confident also that this is not the burn mark so let's go have a look elsewhere now as many people in the comments spotted these are for capacitors reefers a brand of these safety capacitors are filter capacitors that go down to mains earth x class and y class caps and these are actually notorious for failing after a long time because what happens is the plastic casing on these things actually are cracks and moisture gets into them and then if you've got these things like sitting around in storage for 10 or 20 years and then you try and pair them on bang the magic smoke escapes and pretty pungent odor comes out of these things but usually they're quite you know all the ones I've seen are usually quite violent and here's some our photos just pulled off our Google images of various our reefer brand it can happen to other ones but these reefer ones a comment that use these are plastic enclosures they're practically infamous for doing this after you know their 20-30 years something like that and I originally looked at these I went on no they look okay at first glance when we had what looked like a burn mark on the transformer where I thought the smoke was coming out of but upon closer inspection these do look a bit dodgy so I didn't really give those more than a casual glance before but if we look closer upon second inspection I think we can see something down in here it's hard I'll try get the lens down because it's hard to get this board out by the way it it's like yeah it's not easy if you have a look down in there now it seems pretty obvious I didn't notice this but you'll notice that big crack in there like that I didn't see that before and if you can see it big crack down there as well and I can yeah I can feel that there we are there we go get the screwdriver in there so yeah I pays to look a little bit closer and not get caught up in thinking that you've found the culprit especially when I couldn't really explain why that common mode choke would have like caught on fire and smoke - really there was just no mechanism for it so yep that now seems pretty obvious so what I'm gonna do is get all those caps out of there and the good thing about these is that they're not actually necessary for the operation of the unit so I can simply remove them and power the thing back up and at least get it working I mean I you know I should actually replace them and I will of course and you should by the way if you find any old gear vintage computers or any other vintage Teske or anything else that uses these reefer brand caps or similar looking ones for mains input filter in Eva directly across the mains or down from active and neutral down to earth then replace them it's a real good idea because they might eventually go bang ski oh by the way if you get in in there and desoldering like old gear like this there can be like lots of real crusty old flux residue on there and it really goes up in smoke and it's just it's nasty stuff I have actually have been at a job where we actually set off somebody in the lab at like repairing old gear and they bought some old gear in at once and started working on it nope fire alarm went off built in evacuated and yeah lots of red faces all around oops yeah look at that lots of it whoo I think what they've actually done with this thing is the board actually gets assembled onto the transformer the transformer dropped in all the wires are plugged in and then they screw it down like this I've unscrewed the transformer it kind of sort of comes out but there's lots of wires just like some of them are permanently connected and stuff like that so forget the bottom plate on I can kinda sorta get in there and maybe get the D solder the board off but jeez it's it's really quite annoying well yep that's obvious isn't it look at that and if that was just sitting on the board like that would have been just so obvious that this thing was blowing but because it was like you know tucked away in there and it was harder to see you can see it's like bows out and expanded all of the cases just completely cracked everywhere like that big - big splits on the bottom and yep magic smokers escaped and all the other ones look real dodgy brothers to look and see the cracks in there look at all wow that's just yep look straight across but that's you know most of these other ones we're impossible to see inside there once again you might go out and probably see maybe the Bulge and the cracks these things are just absolutely hopeless as practically a hundred percent follow your rate in fact there is a hundred percent fo your rate on these Wow and lucky last there you go yep all completely dodgy and these smaller ones are the Y class caps and the Y class caps are go from active and or mutual down-to-earth whereas this one is an X o'clock yeah X class and half an X class and darkest half the magic smokers escaped and the X class goes directly across the 240 volt or 110 volt mains so there you go yep classic reefer capacitor failure yep it would have been bleeding Lee obviously if they weren't sort of like hidden away in there and we didn't have the other red herring that we chased with the transformer so there you go easy peasy so according to the schematic this one was a 5 micro farad job and the only x2 I have to hand our brand new is this naught point one mic one and look it doesn't really matter 5 micro farad's actually is for the 50 60 Hertz model it's actually lower value for the 400 Hertz capable thing and we're only talking about a you know basically a filter in here so as I said this thing will at work without any of these caps are installed there just are suppression filtering caps basically so I don't know I could try this or maybe I could like steal some from an old board perhaps something like this here's a bunch of well there they be yep there x2 class cap so 470 and there you go so slightly larger so maybe I can steal some for them and these look like Y class caps in here you can tell because they're actually going to ground here you can see that they're across there like that so they're actually going in there to ground but the part number fortunately it's a bit odd ball and these ones are actually a x1 and y1 class cap so they're quite nice unfortunately very low in value 101 there would be 100 or a hundred puffs but hey check out that one that's a 820 nanofarad Y class cap noise and of course once again because it's Y class you see it going over to ground here so as you can see it's handy to have like a scrap board like this in your jumping because you can you know these are still a great quality cap so you can you know suck these out and use them if you've got like an old bit of gear that's you know all the magic smoke all the snots escaped from his old reefer type or other brand you know X or Y class caps then yeah you know these are perfectly good to use so as I said these are X class capacitors in this case x2 which is the second highest rating 1 x1 is actually the highest and you can get lower than that but x2 is by far the most common and y2 ones which were there this one just says y so I'm you know it's a really old one so I'm not sure what the deal is there but anyway but they are designed for different purposes as I said the X class goes across the mains and they're designed so that they don't fail short ie they don't catch on fire because it's directly across the mains it's got low impedance lots of energy behind it so they're designed not to explode um that that was the plan anyway yeah these older ones do unfortunately degrade over time but they're supposed to not do that whereas your Y class caps are designed to go from active or neutral down to ground and they're designed not to have any leakage at all down to ground so they're designed for different purposes now you can actually use a Y class cap in the X configuration but you can't use an X class cap we shouldn't use an x-class cap in a Y class configuration it's just a safety thing you can see some ooze down there on the board that's just spewed out at the bottom of that cap we'll just clean that off before we put a replacement in one of the problems with Sol during a board in situ like this when it's vertical like that is the soda actually with large like ground planes with no soda mask the soda actually falls down under its own weight under gravity so you really have to flip this board up horizontal in order to sold it properly I've just got a regular like a tinned copper PCB like this one right so I'm actually fairly confident to turn this back on now because I'm pretty darn sure that there's nothing wrong with that transformer we've taken out all the X&Y class caps I mean we we had 5 4 5 failures there that's just insane I don't have any y class eye caps in there which are power these two neons as well as are doing some filtering down to earth now a few people in the comments and quite a few actually mention that possibly this thing could have died because I was like a pulse in this thing without a load and there's absolutely no way that I can imagine where that would cause a problem because this bigger sphere that's what this big ass filter and this big ass choke do here and that's the whole point of having these enormous things so that all the output pulse all the output pulses on here don't affect the input and not having a load on there shouldn't be an issue whatsoever so um let's just pair it on and see what we get yep we're back up and running sweet as you go and I've got a course that seated that chip back in there so that's maybe why I couldn't like before it and the magic smoke escaped I couldn't actually I get any pulses on the scope so I'll hook up the scope again give it a ball okay switch the output on bingo there's a sine wave beautiful let's see if we get a pulse on it and of course as I've mentioned when you're doing tests like this high voltage stuff you need a proper high voltage probe available in the eevblog store plug my merge a lot of people don't know that I sell this it's a very nice high voltage probe divided by a hundred beautiful and it plugs straight in with the banana jacks okay so I'm going to set it to a hundred nano second pulse here just symmetric or whatever I'm gonna set it to our five hundred volt pulse and we're gonna single pulse this thing and we set the scope up for a hundred to one probe because that's what our high voltage probe is and we're at 200 volts per division there so let's run that you can see that's actually live so what we want to do is set our trigger point just above that there you go so it's now free running we'll put it on normal mode then we'll single-shot capture that now if we trigger it hopefully we'll capture something it's the plan Wow yep got one something in there that's how it doesn't look like there's anything in there but aha because it's only a hundred nano second pulse and we're currently at five milliseconds per division bingo there it is leave that and that's at 20 nanoseconds per division forty so you know it's roughly a hundred down a second pulse something like that let's actually set it for ten nanoseconds and see if it's faster so I'll keep the time base like that and single-shot capture that again ten nanoseconds and single bingo ma it's the same bueller bueller let's try again it's the same again ten or hundred nanoseconds doesn't seem to make much of a difference Oh anyway it's working and if we change the polarity on there sorry about the glare of the screen um yeah I do have like an anti glare filter I just haven't put it on yet it's a great scope but yeah the screen glare is terrible um I've changed polarity and let's zoom in and bingo is our pulse nice and I'll double the amplitude I'll single shot it again and oh there we go it's a bit problematic um it's it's just picking a random location on the waveform cuz I'm just free pressing it here so I've actually set it to one kilovolt pulse this time and let's sync here we go that's l1 kilovolt pulse it's not huge is it so we're actually working a treat there this is a winner winner chicken dinner so there you have it as predicted in the previous video this thing actually works I didn't think that'd be anything hugely wrong with it I just think it was just so plus two requirements or whatever maybe you know it doesn't support the new testing standard their testing 2 or whatever but and it's probably been sitting around for a long time which is why these damn reefer caps have failed and these are you know like notorious for failing like this it's just like over long term the modern ones are a lot better but these are older ones just absolutely horrible they're they're infamous for doing that so if you've got any old gear or anything with these just replace them as a matter of course even if they haven't failed especially if the thing has been like I believe it's different if you keep them like you know powered up 24/7 for like you know 15 20 years or whatever I believe they're they actually do have a longer life but yeah if you put them in storage and then just try and pair them up and they've got moisture in there or whatever it's like poof well the magic smokes going to escape in this case we were five four five I mean all of those have failed they've all got crap in the case or what not that they just look horrible look at them it's awful and that's how bad these things are five four five unbelievable but it looks like we've got it working I'll eventually get some my class caps to put it back in there and you know restore it to its original thing but it looks like I have roughly working you know you could try out all the functionality and everything but that could take some time but it seems to be generating the pulses that we want so that's a very nice mains interference simulator for the lab awesome test our products now just pulse it in there see if they fail terrific stuff anyway if you liked the video please give it a big thumbs up because that always helps a lot and you can discuss it down below in the comments or over on the EEV look for catch you next time [Music]

Channel: EEVblog

Views: 95,902

Rating: 4.940908 out of 5

Keywords: eevblog, video, rifa capacitor failure, rifa capacitor replacement, rifa caps, rifa capacitors, capacitor failure, x class capacitor, y class capacitor, mains capacitors, filter capacitors, bad caps, bad cap, bad capacitor, blown capacitor, repair, capacitor repair

Id: XAbrU17hLTM

Length: 19min 4sec (1144 seconds)

Published: Sat Feb 23 2019