EEVblog 1511 - Solar Analytics System FAIL! (+ Dave gets ZAPPED!)

The magic smoke was released from my solar analytics monitoring system. What was the culprit?
Also Dumb Dave™ gets ZAPPED!

00:00 - Solar Analytics monitoring system failure
01:58 - Contact probing mains voltage check
03:08 - Inside the infamous fuse box
04:11 - Bench teardown
04:36 - Hey, this thing rattles, WTF!
06:04 - Dumb Dave gets ZAPPED!
08:22 - The missing diode
09:51 - Yuck!
10:59 - The AMAZING resistor!
12:47 - For the MELF fanboys
14:16 - This Supercap looks suspicious...
17:09 - It spewed its guts

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#ElectronicsCreators #solar #fail

[EEVblog]

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.

[christianelzey]

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

[markburton]

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.

[GuyFromJupiter]

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.

[QuanrumPresence]

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

[randalljones]

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

[flubba]

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.

[mysockC]

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

[Rob_]

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.

[solaranalytics]

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

[TeraVoltLabs]

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!

[OneBiOzZ]

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

[LawpickingLocksmith]

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.

[DavidKenny]

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.

[Starphot]

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!

[LarsLarsen]

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

[Jedda]

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!

[mysockC]

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.

[UFO_researcher]

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.

[tweedDaveH]

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..😟