UPDATE: quite a few eagle eyed viewers spotted that R14 was missing. R14 is one of the balance resistors across the supercaps. That falling off could certainly have eventually triggered the event we saw here. I cannot find the resistor, but upon inspection of the pads it was clear that the resistor was soldered in there at one point, but the joint appears like it cracked so to speak. So it could have been a poor solder joint that ultimately lead to the failure. Indeed, the unit likely wouldn't have survived long at all if R14 was missing from production. The resistor could have fallen out on handling and transport to the lab. I have spoken to the designer and the balance resistors were chosen to prevent imbalance and hence overvoltage in the supercaps, and there have been no other reported failures in over 70k units installed. He also concluded that the unit wouldn't have survivded this long if missing from production. In any case the latest design they are sending does not have series supercaps like this. I'll try and do a teardown when I get it.

6:11 Used the BigClive method of "I'll just go ahead and discharge this cap with my finger to be safe..."

30 odd years ago a colleague got a zap from a board across his hand - no damage. All such incidents had to be reported. Some time later he was asked about the incident with some health and safety guys. He showed them what happened with another board. Of course the caps got him again - much swearing.

The last time I got shocked was because I used a 1000V insulation tester to check some 5kV cable for suspected damage while it was still on a reel (it turned out to be fine). What I had not considered was that the conductor and foil shield together essentially made the cable a big capacitor, and that charging it up to 1000V and discharging it across my thumb would feel less than pleasant. 0/10 would not recommend.

As an electronics tinkerer, if you don't get zapped every so often, are you even doing anything? Thanks Dave for keeping it real

" Zappy zap! I just got zapped! " Needs to be on a T-shirt.

I love how the electrical panel is just perf-board and random hookup wires…

Dave has an ElectroBOOM moment!

I've had a few bites from 120Vac (usually a bad ground from a guitar amplifier) but the ones that caused more injury were DC - at Tektronix (Wilsonville), someone 30 meters away blew off their finger on a 5V, 120A power supply... got their wedding ring across it. - 12V DC (motorcycle gel-cell battery) fused a metal watchband to a lady's wrist when I was working at the place that made the first AED. - ME? I got 5kV in one hand and out the other troubleshooting an early-production AED which had a badly mis-wired High Voltage section... someone in production got lost q/all the white-only 6kV silicone wire and somehow failed to connect up the dead-man relay properly so the 50ohm dump resistor was never across the Defib Cap... not even the 1000:1 voltage divider was properly in-circuit, so when I checked the cap looked like it was drained. I got within about half an inch and a BEAUTFIL Bright Blue Spark leapt from the cap and met my fingertip... then up through my arm, across my back (the scapulae met in the middle) and down through the other hand, jumped the anti-static mat (breaks down at 600 volts) and back to the unit chassis, which was siting on the mat. Stupid me, I forgot about the mat's breakdown voltage and thought I was "Safe" with my hand almost 2 feet from the unit. Yer not the only Dumb one, Dave. I think my T-shirt should say : Safe Not By Design... By Luck

Oh no! Sorry to hear the device is dead. We'd love to help you out and will be in touch!🌞

The gunk under the resistor is from the glue used in the reflow. That is a double-sided loadout of SMT parts, they would be all reflowed at the same time, the ones on the bottom have a dot of glue to hold them on during the reflow process. When the resistor heated up to such a high temperature, it burned/melted that glue under it.

im now starting to think that my completely passive reactions to being shocked might speak more towards my carelessness than my experience

Ahh this reminds me of the memories of taking Kodak cameras apart at 10 years old and being blasted by the 400v 100uF capacitor! I never trusted a circuit board without discharging every cap for years!

I remember one morning walking in to work doing a small DVD warranty job, and the cap got me. No coffee needed that morning Dave.

When detecting the 2 supercaps in series I immediately got concerned about them being balanced. @gorak9000 mentioned this too: supercaps don't like to be overcharged to a higher voltage and when placing supercaps in series there should always be some protection to prevent that from happening. Balance resistors are great for small caps (we used to design high voltage capacitor banks that way) but for those large supercaps balancing resistors are not enough. At least some zener diodes or even better one of those active balancing chips especially designed for supercaps should have been used. But writing this I do remember that, back then, I was advices to just place balancing resistors over my supercaps by a component supplier.

Your fuse box isn't old, it's just goofy as fuck to anyone who's from a normal country with normal things.

Solar system analytics fail... meh, I'll watch later. Dave gets zapped-INSTAWATCH! 😂 I predict 6:11 will be "Most Replayed" once the watch graph appears.

You must admit, that diode held on for dear life before it actually failed.

Dump it mate! I grew up on 220V 50 Hz. Got zapped endless times. Then went to England and got zapped on 240V Hey the extra 20 make you taking extra care. Then I had 117V 60Hz, that was just a near pleasant cribble. Next stop: Western Australia in 1982: They had 254V mains!! Never even wanted to get zapped.

Must have been a 'zap Dave day', as I got a 'tingle' changing the back light led strips in my LG TV, even though it had been powered down for over 8 hrs!.. Darned led driver psu caps... Cheers from a miffed Dave in the UK..😟

Interesting video and great to find the point of failure - also great to send the vid to the maker for an excellent feedback tool. Cheers mate.

That second SuperCap might have had problems also as you can see the shrink-wrap cracked on it as well (18:33). Although there is a chance it was damaged by it's neighbor.

Great analysis! Thanks for showing, including your little zap.

I saw the caps as you split the case and thought, “hope he checks for charge on the caps before he proceeds”. I usually check with a meter but the thumb works good too! 😅. I learned the same lesson 30 years ago. Love your videos!

The crispy-fried resistor sort of makes sense since it looks to be part of the snubber network on the primary side. I would hazard to say that D8 that looks kinda cooked as well might be a TVS (Edit: It is. A 200V Zener. I'm sure it got toasty piping hot!). With it there absorbing some of the excess energy the supply probably sort of worked, but once it cracked there was nothing to stop the flyback voltage from sailing away, probably from having the output loaded down or some other issue. I'd guess the caps started to go short-circuit, or possibly it was no longer in regulation and running in some form of quasi-open loop and overvolted everything.

ElectroBoom approves of the pain inflicted in this video.

Thanks very much Dave, having always been a Mechanical Engineer thanks to you I am slowly learning about sparky things lol. You are one of the best Lecturers in the University of KZfaq, second only to ElectroBOOM!

Thanks for the videos, you are extremely smart. The vapors of the electrolyte condense above them when they got hot, causing the upper gross deposit.

Some caps you just cannot discharge, especially there are caps on the other side of a transformer. Discharge a cap on one side, the caps on the other side charge up. This happened in a module in a fire control black box in an attack aircraft while I was in the Navy. We sent back the module repaired, bare as with the other type of modules with the document in its own heavy duty vinyl weather bag. Well, it bit a guy in supply and henceforth that module and others like it had to be in a separate heavy duty document bag or other container. Kudos for the SA guy answering this vlog!

I am soooo relieved seeing the backside of your fusebox - I can now claim my fusebox looks slightly better organized than Dave’s!

A decade ago I was living in a little Victorian era cottage built in the 1860's, so because of its age the power was installed many years after it was built, with all the conduit installed on the walls and ceilings. It also still had the original fuse box complete with ceramic fuse holders and the obligatory packets of fuse wire so you could repair a fuse when it melted. None of that smart meter rubbish!

I never understood how you don't get shocked in your videos... I just assumed it was because you're an amazing EE but its good to see you're also human! haha

Cool video Dave, love the carnage.. hell of a zap.. be good to see what monitoring solution you come up with!

Thank you Dave, your videos are educational and so funny / entertaining ...

New one will fit in the same box, just will have a nice big DIN rail box to hold all the breakers and other DIN rail mounted units, with the meters now all being on the top row in a line. Plenty of space then for extension. When you replace the heater, insulate all the hot water pipes both outside and inside the roof, so as to minimise the heat loss from the long runs.

Supercap in Series is like charging battery in parallel the Voltage get unbalanced or overvoltage on one side over the specifications

Forty years ago I was fault finding a Yankee made telecommunications impulsive noise test-set that had been converted from its original 120V to 240V for operation here in Australia. The bloody thing weighed a tonne, the Yanks had obviously built the case on it out of leftover Sherman Tank steel panels from WW-2. Anyway I wanted to turn it over on the repair bench to measure some voltage readings on the rear circuit board and so I grabbed one of the case front metal handles with my left hand and put my right hand under it to lift what I thought was just the metal chassis but as soon as I lifted it off the bench I copped it with full-bore 240AC surging through my entire body. I lost all control of my muscles and was left standing there with 240V rippling through my chest, and shaking violently and uncontrollably with this damn thing held in a vice like death grip that I couldn’t release and the only thing that saved me was that after a period of time that seemed like it would never end it literally tore itself out of my hands because of its sheer weight and fell crashing down upon the bench, whereupon, I fell crashing backwards and just by luck happened to fall into the seat of the chair positioned behind me. That was, and still is, the closest thing that I had, and have, ever experienced to me leaving this mortal coil, on that day. To close this story, when I later investigated what had caused me to receive this life threatening shock, I found that whoever had previously done the conversion on it from the original Yankee 120V wiring, to the 240V Australian supply, had left the majority of the original Yankee Mains wiring in place , which included the on/off switch on the front panel breaking the Neutral, instead of the Active, and the ‘un-switched’ Active wire then continuing around to the rear of the unit and being terminated upon a ‘bare’ completely un-encased, 3AG fuse holder that was positioned right in the middle of the low voltage 12 volts secondary power supply, and it was that bare, and live, 3AG fuse holder, that the fingers of my right hand had touched when I lifted it off the bench. Unbelievable stupidity, by the Yanks, in the first place, for such a dangerous design and build, on the damn thing, and by the unknown idiot, who subsequently did the 240V Australian conversion on it, and finally by me, for relying upon the front panel mounted power switch, on it, to turn it ‘Off’ instead of turning it Off at the bench power point, before I tried to lift it to turn it over. It taught me a very valuable lesson that day, however, to NEVER, ASSUME, that ANYTHING, Mains Powered, is wired correctly, before you work upon it…!! 🙄

Opening the case halves is easy by inserting flat steel pieces in the rectangular holes on one side and releasing the plastic latches.

I remember the time I learned about caps. I tore apart a disposable camera, the flash cap got me good. I was and am still surprised how long it held its charge. Love it

i can imagine what that zap felt like, i got zapped when i touched a charged flash capacitor in an old disposable camera!

As a young TV tech trainee, I picked up a colour TV picture tube. When the HT ultor got near my chest, wack, instant discharge! Ouch, that hurt! I managed not to drop the tube and never did that again... lesson learnt!

Thats why I used a 50-100 ohm resistor to charge the supercap, but provided a diode bypass for discharge. This way, even if the cap fails short, you only heat up the resistor way within its power handling capabilities.

Just gave this one a like for no other reason than the cap biting you. You earned it.

Well I guess many people can relate to that capacitor shock. Reminds me of the time one of our suppliers send me one of their new and "improved" replacement models for verification, but they forgot to add the discharge resistor and I found out the hard way when unplugging it and got shocked on the dangling plug. Since then I'm paranoid and short every plug on a metal surface after pulling it. I guess in your case it isn't really needed since usually you wouldn't have a plug on that thing, so depending on your standards it may not be needed, but in my case it clearly violated some basic electrical codes/standards here that required the voltage to drop to safe levels in something like 5 seconds.

"Matsushita, they're actually good capacitors" - said Dave's thumb after testing them

Yep, I've had a few shocks like that myself. Each and every time it's from powering up a piece of gear on the bench after repairing it, and stupidly handling the board with my bare hands, moving it to get a better angle for probing. One time I could even feel the 50Hz on the secondary of the transformer, and I had enough time to think "that's probably not good" before I started to put it down, evidently coming into contact with the primary in the process, which caused the muscles in my hand to twitch and throw the board across the room. The last time my arm flew off and smacked into the side of my desk. That one really hurt. I couldn't even close my hand to pull out the power plug.

Ouch! I could feel that shock!

I read Dave gets zapped,and the video opens with you at the box. I thought "oh no!" Then you open the device and I saw those caps, then I knew!

I’ve lost count as to how many supercaps I’ve changed out at work on the bench. They are notorious for leaking and destroying boards, components and tracks.

When I was 15 I got thrown by a 400V DC pull up cap for the CRT screen I was playing in. Cap the size of beer can. My hand was sore and shaking (like the rest of my body) for a few hours. Think I was thrown from the DC shock, as I did have my other hand on part of the chassis. At 15 I didn't know that alone was a no, no. Never mind that the sucker on the back of the tube could carry +400V for long after the CRT was off. I got "bit" by a laptop power brick last year. Unplugged it and grabbed the mains plug. ZAP! Obviously those scrubber caps are getting higher value for efficiency!

LOLz, happens to us all. Normaly you don't get zapped, but when something is fulty you never quite know due to the fult condition.

That split rotated R24 reminds me of an incidents at work back in the day when IC sockets were still widely used, we took a lightning strike which came down into the racks. Burnt ICs were literally physically ejected from there sockets.

I love how, in spite of limited first hand electronics experience, just KZfaq has by now burned in my mind: see a big cap on something recently disconnected, bridge it before getting your hands anywhere near

When I read "Dave gets zapped", I was anticipating it. When you started talking about the capacitors, I thought, that would be the moment. And in the next second - ZAP!!! Just could not predict it more precisely ... 😁 I know it hurts! Once I got it across my thumb and index finger while repairing an extension cord. It was like a heavy hammer hitting my hand. As they say, unplug before open ... 😃

Ah - the memories of copping a boot of a capacitor... I had the pleasure of fixing a Fluke 5215A Precision Amplifier with a burnt out section of board in the 2kV line... That was a long repair job.

Surface tension in the solder pool will rotate components, I expect thats what happened to the half resistor.

I have a suggestion Dave. You should video a break down of the new one checking PCB and quality of solder joints on the new unit, if you do replace it. Could help with future diagnostics.

Years ago I was running a small bare tube HeNe laser and even though I was well aware that the tube acts like a cap andholds a charge for several minutes after being turned off I managed to brush it with my right pinky while moving another HeNe tube and oh boy did that hurt like hell. I don't know how much voltage was still on the tube but I know it operates on 1250VDC and had enough on it to make my finger go numb for a good 20 minutes. Of course the one time I didn't put gloves on was the time I managed to touch a charged tube. That's one mistake I hope to never make again.

Huston. We have a problem! 🚀🚀🚀... That was a shocking experience Dave 🤣🤣 ⚡⚡⚡⚡

Dave trying to do a Mehdi by touching that cap before checking it has some bite left in it.

That's cool - Point-to-point wiring behind a pegboard with DIN mounts everywhere. Never seen that before.

Sir, I just went through some of the "juicier" comment threads up there, and I have to say I admire your patience and persistence with the contrarians and gatekeepers. I hope you don't stress yourself too much feeding any trolls - it's probably worse for one's heart than the occasional zap.

Since it's a two-sided load, one side of the board will have all the SMT components glued down so they stay on until it gets cycled through the reflow oven. That may be the source of the bunk under some, but not all, of the destroyed/lost components.

oh.. nothing like the good old mains-rectified 300vdc, sure works better than coffee to wake you up in the morning

We seem to take bleeder resistors for granted these days. It took a similar experience with a 1000W PC PSU to finally buy a cap discharge tool since it nearly melted my screwdriver and scared the s... out of me!

it seems like power on/off cycles (I dont know if there was any) constantly overloaded the diode because of those beefy hsr super caps. thats my guess. I felt the zap while watching. Hope thumb is recovered. love your videos. take kare.

Speaking of electrical zaps - years ago I was mowing the paddock with an old Victa which had the fuel tap just above the spark plug, and the only way to turn the thing off was to close the fuel and let it run out. I woke up about 10 feet behind the mower on my ass - the mower was stopped so it either ran out while I was out, or I stole all the spark....... probably 10 years old at the time.

I remember when I had my first zap from a capacitor😂 I was about 12 or 13 years old and I was taking a TV apart to see how it worked 😆 the TV had been turned off for weeks, maybe months! I was quite shocked 😂

6:00 - 6:24 lol, that's what she said! :) Happens to the best of us mate. Hope there were no lingering burn marks

That supercap ascended from having ESR to full blown SR. 🤟

I haven't seen every video, but I've been watching for years and this is the first time I've seen Dave get zapped.

6:12 Electroboom is proud of you!

"Solder Bodge"! Man, Dave turns a colorful phrase!

10F at 2.7V equates to around 36J. So definitely quite a jolt. The diode and resister must have reached at least 220°C in order to melt the solder. With the parts of the resistor being light enough for capillary action to keep them on the board.

I got a cap zap from an Amstrad satellite receiver box in the 90's. It had been on the shelf at least a week before I opened it.

Hi Dave, I haven't seen a flipped torn component yet, but I have experienced a self desoldering triac in a TO220 case in our customer's rig. That's why I'm not writing, you already know why you got hit by that capacitor, I dare say I figured it out, because you forgot to put the jazzyk at the right angle and that caused a disturbance of the field of concentration on the distribution of components in the board 😁 All that remains is to say, that they have it nicely designed. Nice day 🙂 Tom

Charged capacitors can be beasts... I once had a power supply disassembled on a Friday and continued working next Monday and then it bit me in my finger! The dam cap was still charged.

I brushed my thumb over a charged capacitor from a old disposable camera that I took apart years ago and it put a hole in my thumb, lol.

Biggest zap I've done is 120v ac. One time barely noticeable, another time I was white for the afternoon. Glad to see you'll make a full recovery.

R24 most likely rotated during a EOS type failure. We make a design EOS/TLP pulsers and its common to see components physically eject themselves from PCBs.

i do like it when they put spare part in side for you, in case they are needed later

You are now an official member of the ElectroBOOM club!

I was investigating the power supply for a PoE network switch a few years ago. It had been sitting, unpowered/unplugged for at least a week. Well, before I knew it, I involuntarily threw that PSU board across the room, big zap! Turns out the power planes went all the way to the edges of the roughly cut PCB (seemed scored+broken rather than sawed/milled), and handling the board by the edges as I always do, was exactly the way to get zapped :) Good times. Now that I think about it, it seems a bit odd that the high input filter cap voltage would be present on a big power plane though going to the edges of the board though...

It got hot enough to melt the connections, then cracked, then gravity took over. The gunk underneath is what's left of the glue. When they do low end boards like this they'll glue the parts on the bottom then use a mass soldering technique like wave soldering.

Once got a 1000VDC zap from a PMT power supply by somehow touching my probe with a metal braided shield touching the back of my hand - man I had 3 fingers numb for a few months doc even sent me to the neurologist where they did an EMG with a sharpie and marked where the damage was (ulnar nerve I think) - thank goodness it healed on its own - high DC voltage is no joke m8 glad you're OK

As you were holding the board I knew you'd get zapped. It was pure luck you weren't stung earlier. lol. I've only seen resisters like that once. It was caused, or at least what the engineer who came to fix it said, by lightning. It had struck one of the phone line relay boxes and had caused numerous, he said almost 30, wifi routers, to fail in the immediate area. He didn't have that many spares in his van so would come back the nest day. He left the damage one with me and told me to throw it away. But I wanted to see inside. numerous SM components had come off and I saw one like yours all melted and twisted.

OMG. I was totally okay with this "fuse board," it was just, "alright, so it's old, whatever." THEN IT OPENED.

I've seen a resistor fail like this, but only once before... A customer's vehicle was struck on the little aerial on the roof of the vhicle, and the control unit for the telematics had failed inside the MCU itself. It seems as the though the resistor slowly heats up until the soldr melts, however the resistor continues to heat up slowly until it fails. When it seperates, the component breaks in half due to the heat and the solder is still molten, so the surface tension of the solder on the 2 halves of the resistor pull it in stange ways...

Seems like it was a Flyode trying to escape. 😂 Thinking of where the electrolyte drips seems like a valid thing to look at when you are doing a FMEA for a critical part.

The isolation between AC mains and secondary circuit does not look safe on the power supply board. The 3G antenna is accessible so there should be double/reinforced insulation on that power supply. This kind of equipment should be designed taking over voltage category III requirements into consideration.

The diode may have been the initial failure, with the leakage causing AC to appear across the super caps which they would not have liked.The excessive current draw then cooked the primary side resistor.

Thanks for the video. The resister needs to go straight to the pool room.

That was shocking! Ok, I'll show myself out!

If you didn't already know, Matsushita is the parent company of Panasonic and Technics.

Had Issues with nesscap supercaps in the previous company, back in 2015 so it's similar date with your product. They often leaked and coroded the PCB, althoug we were using much bigger size 55F-60F I recall.

One morning I came to work and the internet was down.Investigating the issue I found the router was off. A cap had blown in the wallwart PSU. This had vented through the case by breaking the plastic earth pin off the plug (UK double insulated type) and ejecting the PSU partway out of the socket.

I've had mosfets get hot enough to desolder and rotate. Board destruction shortly followed.

I was once told by an engineer that :- "You are not a proper electronics engineer, until you have been 'zapped' atleast once.... But don't make a habit of it" !!!! 😆🤣 I've been zapped many a time, in my youth whilst working on valve stuff and TV's.... But these days, I am much more careful, and show much more respect to high voltages now🤔

@13:24 Looks like one of the supercaps died. It's a little bowed, and there's the tell-tail signs of schmoo leaking out of the bottom. That would explain the "slow" overload that cracked a resistor and melted the diode. That gunk under the resister is very likely the glue used during manufacture (wave soldering / IR cooking the underside.) I'm really surprised there aren't fuses all over that thing, being mains connected and all. (Yes, I've seen resistors crack. Even the big 1960's era pinned ones -- inside an arcade console powersupply. Moisture gets into them and then heat/cold cycles take their toll.)

That failed capacitor looks like it has small bulge on top, not very noticeable but it is. Also tracks from second capacitor to card connector look broken and lifted a bit. About that resistor my guess is, that it got so hot that it almost desoldered itself and violently cracked in half, thus rotating like that, with solder solidifying right after that.