Well EEVBlog is THE UA-camr for the customoers the builder want's to sell things to. So ignoring or bullshitting such a spectactular video is a big no no for them. They had to address this video in that way they did to not loose any credibility and beeing able to sell products in the future.
This series of unfortunate events was actually really useful for a hobbyist/novice like me. I had never really thought about the mechanical stress issue, and this really demonstrates that it's not something you can just ignore and think will be alright. Could literally cause a fire. Imagine if nobody had been present. At best, smoke alarm, at worst, literal room fire.
Reminds me of a TV repair many years back, where there was a charred area in a board around the horizontal output tube, and the high voltage pulses in that circuit were having all kinds of fun jumping around that area. I think this was before manufacturers caught on to the idea of isolation slots and similar stuff.
MLC caps also have great microphonic characteristics. They can be used as low-grade conducted sound microphones, and can even replace some uses of accelerometers. I once used one as a tap sensor, where tapping a specific pattern would initiate a different operational mode (such as calibration) without need of a full user interface or command interface or even switches. Just be sure to use a pattern that won't be accidentally triggered by normal handling! Such use is stealthy as hell! Impossible to detect just from looking at the schematic or PCB (unless you already know the trick, and sometimes not even then).
Had to fix something similar in an OEM car amp in the power input section. Someone connected the car battery backwards... entire burnt section was really conductive. Ended up having to completely cut out the crispified section of the board and rebuild it with a blank piece of board cut to size and shape. Etched new traces, drilled, and epoxied it in place. Amp worked great afterwards.
The Workbench Yes, I had a similar experience. Now I am convinced that if a board have a burn like this then no cleaning or scraping can save it. The whole burnt spot is completely toast and should be just cut off and replaced with a new piece. But the best solution is generally just to replace the entire board. Even if you need to move some or even most of the components from the damaged board it is faster anyway and the end result is much more reliable.
Nice quick fix! Practical works, but for those curious, full repair would be possible. 1. Remove surface damage 2. Remove all components over/around burned area, and remove solder mask for traces to be salvaged 3. Clean surface, trace or photograph traces. If damage allows, use copper foil and mark/cut out replacement tracks 4. Using small dremel ball mill, excavate until no burn damage remains 5. Use two-part epoxy to fill in damaged parts. Use nylon or plastic if needed to contain expoxy for damage going all the way through 6. Wait for cure time of epoxy and sand surface smooth. 7. Cut replacement traces from copper foil and using light epoxy, place them on the board. Use tongue depressors and clamps to hold them in place until epoxy cures. Do not put epoxy on overlaps with existing traces. Once epoxy is fully cured, tin/lap solder new trace to existing trace. 8. Drill holes for any needed plates through hole rivets with pin vise and bit, by hand. Using a pointed punch and a flat punch, set the rivets and tin them to the trace. 9. If damage is too great or infeasible, for money or time reasons, run jumpers with solid core wire. Or, just use a slotting saw ;p
Kudos to RD tech his analyze in the first video was spot on, hence carbon vapor-residues in the second case and tension in the first case... these RD tech board PSU seems like a decent alternative for extreme budget DC PSUs.
Adding Silicone Conformal Coating to your repair would be a cool touch. Especially since you cut into the PCB, it would protect it from absorbing moisture, etc. Not such a big deal in the lab, but if this was to be installed on a manufacturing floor, or outside, might make a big difference.
13:30 I think in that noise speed, it would be better to use a small value non polarized capacitor to reduce that noise. The original burned capacitor is a small valued capacitor. Electrolytic capacitor will not prevent fast transient noise.
My mom had this habit, gleaned from her early years growing up and raising we children on a farm with very little income, of keeping anything that may one day be needed, even if it needed repair. Well she is 93 now and recently entered the nursing home after several falls needing an ambulance to get her to hospital for treatment, an irregular heart beat was diagnosed and treated, she is doing great now but cannot come home. So it is, I am cleaning our her home to sell for her. I came across an old radio replica of a 1930's set but with modern transistor guts. It had developed a deep hum that I figured was due to filter caps from the power supply, that said the dang thing had the caps on the main board, just a transformer with a couple of inducters on the PS board. At any rate, I didn't have the 1000uF caps at 16V in my kit but I did have some 1500uF at 16V, so I used them. Well the hum is nearly completely gone on AM and there is quiet on the FM (We have no FM stations available in our little corner of the Dakota's) but when I transmit on my tiny FM transmitter it is clear as a bell. So I guess one can go higher as you say with the capacitance with little to no problem, likewise when fixing an old PC Speaker Amp from the 80's I had to substitute a 3300uF cap with a 2200uF of the same voltage rating and again, the device seems completely happy, I have added a Blue-tooth receiver to the speaker so I can use it for general music via my cell phone or PC for the holidays.
"Bob's your Uncle" ---> "you're all set" this is the first time I heard that. Like the phrase. Kinda like another I heard yesterday "Do the needful" --> "Thank you for doing this". Keep broadcasting!
It changes value in FOUR conditions. 1) +humidity, intially it is like a sponge, it will capture any humidity in the air and increase conductivity. 2) if reconnnected, it actually can carbonize MORE. 3) it also reacts on PRESSURE, if it pressed, it wil get more conductivity.... ideal to measure WEIGHT!. 4) vibration, it is like a microphone too!.
Took an 40hr course on multi layer board repair at work and I loved it, but as is typical with these sort of things I never once had to repair a board as part of my duties outside of the class.
THANK YOU! AMAZING VIDEO!! i know im a bit late in watching, but i have a burnt board that i tried to repair some traces on it that i was SURE i had right, but i could never get to work sitting in the fail bin for the last 3-4 years! i had never heard of anything like this before. this is a GREAT tidbit of knowledge that i am grateful i have now, and wish i had long ago. i need to go dig this out now....
I had a capacitor fail thermally on a video card in my older pc and it took the motherboard out as well! It wasn't a mechanical failure of the component but it puffed a few capacitors on the board, just at a glance. I've yet to look closer to see if it's salvageable, even long enough to get the, thankfully, small amount of data off the hard-drives. Thanks for the encouragement. Cheers Dave.
I just changed the electrolytic capacitors in my amp that I use for my computers audio. So this is the first video I watched to test the audio and I'm thinking wow, the audio sounds so different with these new caps. I wonder why? I got the answer at the end of the video. :)
Found your video while looking for assembly guides for the DPS5020, which I just received (in early 2021). Board design is same as yours. Noticed that you spun the board around 180 degrees from the prior video, so that the fan is at the back. That's how I see it most often. It did look like you had the "out" terminals connected to the "out" screw tabs. Really liked how you tucked the ribbon cables under the board. Disassembled mine to do the same. Much neater.
One PCBA manufacturer took it upon themselves to improve their profit margin by changing our board separation design from milled + linked to v-scored (V-shaped groove). The induced stress by bending to breaking the scoring also broke caps near the board edge....
You're doing Glen a big favor advertizing these. I'm an electronics student, hobbyist my bench supply can only do 300w. I'm definitely buying one of these when they come back.
+Ollyweg 0 It is probably there in case you charge a battery, and if the PSU fails (shorts) internally, the fuse will protect against the current coming back from the battery. Definitely worth fixing that fuse, or adding a separate external one instead of the SMD ones. But the sense line may also be need to be connected after the external fuse...
I think that the "EEVBlog repair curse" has outdone itself this time. It was a power supply failure! It was a simple power supply failure! And it was captured on camera. Hooray!
I'm currently also doing output ripple measurements and have read a preferred technique is to DC block a connection to the power supply output and terminate this in 50R at the scope. Otherwise, the normally high impedance input of the 'scope means any currents induced will create large voltages. According to the Analogue App Note I read, the bandwidth should also be set to a low value (20MHz) for comparison purposes.
Exactly my thoughts. My personal favorite filtering solution (for permanently connected loads) is ceramic cap + ferrite bead + larger low ESR cap (~100-220uF). So it's some CLC filtering.This easily drops noise by a factor of 10 for DCDC supplies.
Even 47uF on the output of a variable power supply is considered too high, and it is the highest designers will go. This is because if the cap is charged, it will have enough energy to destroy something if you crank down the output voltage, attach a new circuit, but the cap will be still charged at +30V. Also, large caps on the output do mess a lot with the output current limiting circuit. Small SMD caps are a good idea, but mechanically it has to be designed differently compared to the product Dave tested here.
I had a fun time when i read their "Brand Story" page on their AliExpress shop page. They show a world map where they ship their products there. Of course china is in the middle of their world map :) Funny to see another perspective. However, more fun to see is where they think Uruguay is located (in Russia?), the Netherlands and Belgium is located in Russia as well and France is where i thought Poland would be.
Nice repair video! It's good to see that the fault was easily identified and repaired. They really should have stopped selling the PSU when they saw prior failures in the field, though. A wrongful death through negligence would have been tragic.
Yeah, there is always something... at least the company behind this appears to actually care about their products so I actually would feel comfortable buying something like this, and probably will once they come back.
Hey Dave. I'm glad that burnt the board as you made a great video from it. The modification to cut through the carbonised board was quite neat considering the damage. Well done.
Rd Tech difficult to totally clean off the carbon. Isolating the low resistance is the best you can do. Gets you out of trouble while you order another one if you care about the cosmetics.
Wouldn't a simple mod to resolve the problem be to fit a wire ended cap instead of the surface mount one. The wire ends would provide sufficient resilience to eliminate the stress being applied to the cap when the screw terminals are tightened.
Some ceramic capacitor manufacturers have MLCC SMD offerings which are much more resistant to PCB flexing and have a failure mode with a preference for failing open rather than being a short. Ex. www.avx.com/products/ceramic-capacitors/surface-mount/automotive-mlcc-with-flexiterm/
Brian Oldford That was my immediate thought. I suspect that they just have those MLCCs in stock, saw that they could be soldered between the pins, and so used them. An attempt to polish the product a bit by adding that capacitor ended up backfiring on them. At least they cared to try to improve the product.
But SMD caps are generally used because of their extremely low ESR. So if you add leads or out it further fro what you want to decouple, you're making it less efficient. Am I right?
If you keep the leads reasonably short and close to the board, the lead resistance is so low, its not measurable. Its not as if there are huge currents on the ceramic capacitor leads.
I didn't test it yet but i might swap out the cap for a foil one to avoid any future issues, that board burn was bad! I never thought about carbonisation becoming conductive before. Nice work!
I see this all the time on laptop mainboards. Multilayer ceramic capacitors are sensitive to a lot of things: flex, mechanical shock, vibration (they're microphonic!) humidity, lots of stuff really. You need to be careful with your layout when you are using them in a high current power supply.
The lesson here is that you don't need to torque those PCB screw terminals like a Head Bolt. It takes surprisingly little to achieve zero resistance. Just beyond snug might be best. Just enough to keep from falling out. Rookie car mechanics are always breaking bolts.
I have a DPS5015 and also went black!!!! Simply when I was testing a simple and tiny DC motor with 3V!!! Does not even turn on anymore! Any tips to repair it?! Glen?! Excelent lesson! Thanks Dave!
DC output should be as clean as a cell battery, right? Right. A ripple factor at the output so high and with many switching peaks at 200/300 KHz means that is a power supply with a quality that leaves much to be desired ...
Dealing with the failure of this device made for an interesting pair of videos. Old resistors were made up of carbon. The fire left a carbon deposit on the board has effectively created a resistor that was distributed over an area of the board instead of in a nice cylindrical package. There is still a bit of carbon beside the one fuse on the top of the board. It might compromise the circuit safety should it ever blow from over current. The remaining carbon may still be providing a low resistance path between the two ends of the fuse. Two caps in series will cut the capacitance in half, not double it as you said. You could make a Fundamentals Friday video out of why cracks in MLCC caps cause them to fail shorted.
If you're trying to measure output ripple and noise you need to use a high impedance probe with a ground ring connected directly across the output on the PCB. You can't use shity banana cables, you have a huge ground loop acting like an antenna. Also adding a high ESR electrolytic capacitor across the output (at the end of the wires!) won't help the ripple at all, it needs to be a specifically selected capacitor with the proper ESR and located very close to the switching inductor.
I have one of these modules with the case, not the exact same, but the input cap is gone, or relocated. Problem solved. It works great, I'm using it as a bench power supply and powering it from a computer PSU because of the high output current.
Interesting video with great practical information about these multilayer capacitors and the conductive effect of a burned PCB. On question though: you mention putting two capacitors in series as a solution to prevent shorting-out failures. However, in case one capacitor fails one would not notice that it failed (only less capacity), until the second capacitor also fails, leading to another flaming short-circuit situation. Wouldn't it be better to put a fuse in series instead of a second capacitor? Maybe even better to always add a fuse in one supply line, before the capacitor that goes across plus and minus?
Clear. Thanks for your reply! I guess my poor understanding of the word "susceptible" led me to derive incorrect odds from your the statement at 15:40 ("These multi-layer capacitors are susceptible [...] to not only mechanical stresses [...], thermal stresses, they're susceptible to just a failure in manufacturing [...] infant mortality thing [...]"). Do I understand well that the odds for mechanical stress were in this case greatly enlarged by soldering the capacitor between the poles and that the other potential causes are much less likely to occur? I ask this because in my own projects I have often soldered an SMD cap close to, or even on a regulator and I wouldn't want that to cause a fire. I now wonder how dangerous the placement of the caps is that I chose in projects such as in this video: ua-cam.com/video/K7Lv5FWTX9Y/v-deo.html I know I am probably violating all rules of proper PCB layout in that video, but hope it isn't too dangerous!
@@rdtech9153 it's good to see you following the discussion. I just bought an DP20V021 because you worry about quality and the satisfaction of your customers.
@Max Bambusman we have already solved the problem and updated that , don't worry . from that day, we begin to sell new version , and we did not stop to sell..
I would've removed the fuse, then remove all traces of carbonation, then solder the fuse back on. It will remove all doubts as to any short circuit under the fuse.
Probably cutting off the corner with the terminals, then soldering wires to the proper places, adding an external fuse, then also moving the sense point to the output receptacles would be the best fix.
How would two caps in parallel help? A short is a short. Shorting ceramic caps is a known problem but not something I've experienced much despite the millions we use, quite unfortunate I'd say. AVX have a "flexicap" range so maybe the bigger brand technology is mitigating this problem.
Hi Dave can you make a video about pcb design and track spacing . Would be interested to see if eg pwm, uart, i2c etc do some crosstalk and how close you can layout them without problems. I think measuring that would be interesting
Ive also experience problem on ceramic capacitor that shorts out the power supply and it burns the charging ic for the battery and one other component that seems to be an scr but i couldnt find a replacement parts here in Philippines smd is not that popular in here,we have very limited suppliers for smd component . So is it always the ceramoc capacitor that usually fail in smd component thanks Dave
Well Dave, what should I say? There are reasons for paying for a properly trained engineer with experience when designing products, whether its electronics or anything else. Today's market where "makers" think that they can design build and sell things leave everyone at risk of failure. This failure was mostly benign because you were attentive and understood what to do. But burning electronics can lead to the complete loss of a structure and lives. So this has to be classified as a very serious issue.
I'm sorry, but I have to correct you: a 20 A fuse MUST NOT trigger at 20 A - never. Depending on the standard is has to meet, it might trigger at 1.25*20A after 1h or something in that order of magnitude. Check on google for some current-time-curves, if you're interested in more details ;)
He showed a current-time fuse curve in the freaking video, dude. 7:25 And a 20A fuse run at 20A will eventually fatigue and blow under "normal" use. You don't run any components at 100% of their rated values if you want them to last. It isn't good engineering.
What is wrong with you? Yes, he is showing a curve - thanks for telling me, but at least you definetely didn't undestand it. Just in case you didn't know: This is a logarithmic plot, so if you look at the line for the 20A fuse, you'll see it is only specified to blow at 40A (or more) after 3 sec (or less). The plot does NOT specify anything about 20A for 20A fuse. So if you - as I said - do some googleing, to find other curves, that specify all the operating range of a fuse, you will see, that no normal fuse will blow at it's rated current - ever. This has nothing to do with good engineering, I'm just talking about device characteristics here. There are even standards out there, that require, that a fuse MUST NOT BLOW for any current less than 1.3 times their rated current for several hours. I usually like discussions, but please don't come up with some things that you "think" are true but instead do some research before you accuse the things I say.
I never said, that you should put a 20 A fuse in there. I never said you should always put a fuse in a product, that exactly matches the nominal current of the product. I get that fact, that they were not willing to put a 20 A fuse in there - it makes sense. All I wanted to clear is the common miscconception, that a 20 A fuse blows at 20 A. This misconception is very common indeed and is just not true. If you have a 16A fuse at home in your fuse box, you can draw 20A "until the cows come home". This is what I wanted to get across. Does that mean, you should put a 20 A fuse in 20 A device? No.
3:48 "Burnt fiberglass --", erm, excuse my nitpickiness, but isn't glass mostly silicon dioxide? My best guess for the source of the carbon would be the hydrocarbon-based resins used to laminate the fiberglass layers together.
One of the fuses is stillshorted by carbon. You could move them to the other side of the board, scratching away the solder resist on the terminal and inductor pad.
If this PSU will have load with high short-circuit reverse current capabilities (high input capacitance or simply electro-chemical cells for example) this part will fail with explosion. As there is no safety features it can do same thing while catching a high voltage spike.
Its funny how they admitted that it has happened before, and now they have to fix it because it happened during a review. They didn't care that that had happened to customers in the past. I'm glad that it happened during the review, because if it didn't, they would not of fixed it and would be still selling it to anyone that would buy it. Luckily it happened during the review and Dave knew how to handle it. There are probably a lot of customers out there that had purchased this unit and might have been devastating to them and still not know there is a problem. Not sure how I feel about the company at this point. They knew there was a problem and continued to sell it. They were forced to speak up because of the review and were expecting to gain sales by paying someone to review there product. It blows my mind. They knew there was a problem, sold it anyway, not caring of the results, and they sent it to get reviewed. I also noticed, that Dave usually trashes items like this, and destroys everything about the design including the designer having ugly children or leads were loose or too small, or he smelled on the other end of the phone. There was a few things, that he was like "oh well", that he would of spent a great deal of time about how bad it was. That is what makes me think he was paid to review this product and also do 3 updates about it.
When a builder admit the error and give a solution is so refreshing.
Well EEVBlog is THE UA-camr for the customoers the builder want's to sell things to. So ignoring or bullshitting such a spectactular video is a big no no for them. They had to address this video in that way they did to not loose any credibility and beeing able to sell products in the future.
Not so hot that they'd already seen that failure mode and hadn't taken action in the past...
Most of the reason why I will be buying version 2. I have a LOT of a respect for this guy/company now.
Mike M same here. After this vid, I will be getting one of these for sure.
@@ws_stelzi79 wrong, you need to learn how to appreciate what this builder/designer did, many do not address issues found.
I love the manufacturer admitted the flaw and stopped selling until they fix the issue. Makes me feel better if if ever buy from them.
Dave always satisfied about insulation gaps :) Now he made one!
BMR Studio *goes and cuts insulation gaps in his 5020
This series of unfortunate events was actually really useful for a hobbyist/novice like me. I had never really thought about the mechanical stress issue, and this really demonstrates that it's not something you can just ignore and think will be alright. Could literally cause a fire. Imagine if nobody had been present. At best, smoke alarm, at worst, literal room fire.
I don't think the fire could have spread. The circuit board is a flame retardant material, and it was inside a metal shell.
@@PunakiviAddikti True but I have seen a plastic housing catch fire because of this problem.
Big thubs up, for the manufacturer, for handling the problem professionally :-)
Reminds me of a TV repair many years back, where there was a charred area in a board around the horizontal output tube, and the high voltage pulses in that circuit were having all kinds of fun jumping around that area. I think this was before manufacturers caught on to the idea of isolation slots and similar stuff.
It's so satisfying when you repair your broken electronics
Brutaltronics And then every time you use it after that you feel satisfied all over again!
@Brutaltronics
in fact ,there is not big problem , it is very easy to be fixed
But not when you buy it new lol
@Plan C
now all the products was updated
How do I know I'm buying an updated one ? From which aliexpress shop ?
MLC caps also have great microphonic characteristics. They can be used as low-grade conducted sound microphones, and can even replace some uses of accelerometers.
I once used one as a tap sensor, where tapping a specific pattern would initiate a different operational mode (such as calibration) without need of a full user interface or command interface or even switches. Just be sure to use a pattern that won't be accidentally triggered by normal handling!
Such use is stealthy as hell! Impossible to detect just from looking at the schematic or PCB (unless you already know the trick, and sometimes not even then).
I've done several videos on that.
Props to the designer of the device. Rather than getting defensive they admitted the error and are fixing it!
It's not a fault it's a feature, 50 Ohm output impedance. ;)
73 :D
Had to fix something similar in an OEM car amp in the power input section. Someone connected the car battery backwards... entire burnt section was really conductive.
Ended up having to completely cut out the crispified section of the board and rebuild it with a blank piece of board cut to size and shape. Etched new traces, drilled, and epoxied it in place. Amp worked great afterwards.
The Workbench Yes, I had a similar experience. Now I am convinced that if a board have a burn like this then no cleaning or scraping can save it. The whole burnt spot is completely toast and should be just cut off and replaced with a new piece.
But the best solution is generally just to replace the entire board. Even if you need to move some or even most of the components from the damaged board it is faster anyway and the end result is much more reliable.
@
The Workbench
thank you for your message ,. in fact , it depend the exact products, because some product has no protection
@Кирилл Рагузин
sometime yes, sometime no, it depends on the products and which part was burnt
It was a Honda, but I'm not sure what model exactly, I was just given the amp to look at.
@
The Workbench
you can test to check
RD TECH IS SO COOL. Most hardware designers just ignore us peasants unless our name is AT&T or IBM.
Nice quick fix!
Practical works, but for those curious, full repair would be possible.
1. Remove surface damage
2. Remove all components over/around burned area, and remove solder mask for traces to be salvaged
3. Clean surface, trace or photograph traces. If damage allows, use copper foil and mark/cut out replacement tracks
4. Using small dremel ball mill, excavate until no burn damage remains
5. Use two-part epoxy to fill in damaged parts. Use nylon or plastic if needed to contain expoxy for damage going all the way through
6. Wait for cure time of epoxy and sand surface smooth.
7. Cut replacement traces from copper foil and using light epoxy, place them on the board. Use tongue depressors and clamps to hold them in place until epoxy cures. Do not put epoxy on overlaps with existing traces. Once epoxy is fully cured, tin/lap solder new trace to existing trace.
8. Drill holes for any needed plates through hole rivets with pin vise and bit, by hand. Using a pointed punch and a flat punch, set the rivets and tin them to the trace.
9. If damage is too great or infeasible, for money or time reasons, run jumpers with solid core wire. Or, just use a slotting saw ;p
Kudos to RD Tech for admitting the fault. I have one of their supplies after seeing an EEVblog video about them, and have been pretty happy with it.
Kudos to RD tech his analyze in the first video was spot on, hence carbon vapor-residues in the second case and tension in the first case... these RD tech board PSU seems like a decent alternative for extreme budget DC PSUs.
Adding Silicone Conformal Coating to your repair would be a cool touch. Especially since you cut into the PCB, it would protect it from absorbing moisture, etc. Not such a big deal in the lab, but if this was to be installed on a manufacturing floor, or outside, might make a big difference.
Nice fix and good to see you still think it's a fair product despite the problems.
The biggest mechanical stress on this cap occurs, when terminals cools down after soldering.
Good on you Glen, a lesson for all of us.
13:30 I think in that noise speed, it would be better to use a small value non polarized capacitor to reduce that noise. The original burned capacitor is a small valued capacitor. Electrolytic capacitor will not prevent fast transient noise.
My mom had this habit, gleaned from her early years growing up and raising we children on a farm with very little income, of keeping anything that may one day be needed, even if it needed repair. Well she is 93 now and recently entered the nursing home after several falls needing an ambulance to get her to hospital for treatment, an irregular heart beat was diagnosed and treated, she is doing great now but cannot come home. So it is, I am cleaning our her home to sell for her. I came across an old radio replica of a 1930's set but with modern transistor guts. It had developed a deep hum that I figured was due to filter caps from the power supply, that said the dang thing had the caps on the main board, just a transformer with a couple of inducters on the PS board. At any rate, I didn't have the 1000uF caps at 16V in my kit but I did have some 1500uF at 16V, so I used them. Well the hum is nearly completely gone on AM and there is quiet on the FM (We have no FM stations available in our little corner of the Dakota's) but when I transmit on my tiny FM transmitter it is clear as a bell. So I guess one can go higher as you say with the capacitance with little to no problem, likewise when fixing an old PC Speaker Amp from the 80's I had to substitute a 3300uF cap with a 2200uF of the same voltage rating and again, the device seems completely happy, I have added a Blue-tooth receiver to the speaker so I can use it for general music via my cell phone or PC for the holidays.
Love the new sine-wave EEVBlog logo.
Me too!
It's much better than having a 10-second intro video on every video like some other channels. That gets old quickly for regular watchers. :)
"Bob's your Uncle" ---> "you're all set" this is the first time I heard that. Like the phrase. Kinda like another I heard yesterday "Do the needful" --> "Thank you for doing this". Keep broadcasting!
It changes value in FOUR conditions.
1) +humidity, intially it is like a sponge, it will capture any humidity in the air and increase conductivity.
2) if reconnnected, it actually can carbonize MORE.
3) it also reacts on PRESSURE, if it pressed, it wil get more conductivity.... ideal to measure WEIGHT!.
4) vibration, it is like a microphone too!.
Took an 40hr course on multi layer board repair at work and I loved it, but as is typical with these sort of things I never once had to repair a board as part of my duties outside of the class.
THANK YOU! AMAZING VIDEO!!
i know im a bit late in watching, but i have a burnt board that i tried to repair some traces on it that i was SURE i had right, but i could never get to work sitting in the fail bin for the last 3-4 years! i had never heard of anything like this before. this is a GREAT tidbit of knowledge that i am grateful i have now, and wish i had long ago. i need to go dig this out now....
Nice followup video. People usually just throw all old equipment to trash or "recycle" when simple repair is possible.
I had a capacitor fail thermally on a video card in my older pc and it took the motherboard out as well! It wasn't a mechanical failure of the component but it puffed a few capacitors on the board, just at a glance. I've yet to look closer to see if it's salvageable, even long enough to get the, thankfully, small amount of data off the hard-drives. Thanks for the encouragement. Cheers Dave.
I just changed the electrolytic capacitors in my amp that I use for my computers audio. So this is the first video I watched to test the audio and I'm thinking wow, the audio sounds so different with these new caps. I wonder why? I got the answer at the end of the video. :)
A nice demonstration that we learn more from failure than from success. And thanks for the video, is nice to see how to solve such problems.
@Josuel Servin ,
good lesson
Found your video while looking for assembly guides for the DPS5020, which I just received (in early 2021). Board design is same as yours. Noticed that you spun the board around 180 degrees from the prior video, so that the fan is at the back. That's how I see it most often. It did look like you had the "out" terminals connected to the "out" screw tabs. Really liked how you tucked the ribbon cables under the board. Disassembled mine to do the same. Much neater.
I was expecting this satisfying repair, good job!
One PCBA manufacturer took it upon themselves to improve their profit margin by changing our board separation design from milled + linked to v-scored (V-shaped groove). The induced stress by bending to breaking the scoring also broke caps near the board edge....
You're doing Glen a big favor advertizing these. I'm an electronics student, hobbyist my bench supply can only do 300w. I'm definitely buying one of these when they come back.
The charred board underneath the fuse will bridge it. It won't blow at 20A anymore...
So what. Safety schmafety. This is not a mains PSU.
+Ollyweg 0 It is probably there in case you charge a battery, and if the PSU fails (shorts) internally, the fuse will protect against the current coming back from the battery. Definitely worth fixing that fuse, or adding a separate external one instead of the SMD ones. But the sense line may also be need to be connected after the external fuse...
Thanks for following through with this Dave. I learned something as usual.
I think that the "EEVBlog repair curse" has outdone itself this time. It was a power supply failure! It was a simple power supply failure!
And it was captured on camera. Hooray!
I'm currently also doing output ripple measurements and have read a preferred technique is to DC block a connection to the power supply output and terminate this in 50R at the scope. Otherwise, the normally high impedance input of the 'scope means any currents induced will create large voltages. According to the Analogue App Note I read, the bandwidth should also be set to a low value (20MHz) for comparison purposes.
Wouldn't a small ceramic cap do *better* at noise filtering than a 22uF electrolytic cap?
IMO anything wire ended would resolve the problem. See my comment above.
Exactly my thoughts. My personal favorite filtering solution (for permanently connected loads) is ceramic cap + ferrite bead + larger low ESR cap (~100-220uF). So it's some CLC filtering.This easily drops noise by a factor of 10 for DCDC supplies.
Even 47uF on the output of a variable power supply is considered too high, and it is the highest designers will go. This is because if the cap is charged, it will have enough energy to destroy something if you crank down the output voltage, attach a new circuit, but the cap will be still charged at +30V. Also, large caps on the output do mess a lot with the output current limiting circuit. Small SMD caps are a good idea, but mechanically it has to be designed differently compared to the product Dave tested here.
Put a high value discharge resistor in parallel?
You are correct, I use large caps on output of DCDC only for permanently connected loads.
I like Glen. Everybody: be like Glen. Glen good.
Well done Dave. Thanks!
@Proyectos LED
are you satisfy now ?
For tasks like this one I would also recommend investing in a glass eraser pen
I had a fun time when i read their "Brand Story" page on their AliExpress shop page. They show a world map where they ship their products there. Of course china is in the middle of their world map :) Funny to see another perspective.
However, more fun to see is where they think Uruguay is located (in Russia?), the Netherlands and Belgium is located in Russia as well and France is where i thought Poland would be.
LOL you should have taken a printscreen! EDIT: it still there! (So exotic!)
Nice repair video! It's good to see that the fault was easily identified and repaired. They really should have stopped selling the PSU when they saw prior failures in the field, though. A wrongful death through negligence would have been tragic.
I am glad to see some stuff like this covered, I am looking into getting a cheap psu and its good to see that there are good and cheap.
the quality has no problem, just the capacitor place is not good
Yeah, there is always something... at least the company behind this appears to actually care about their products so I actually would feel comfortable buying something like this, and probably will once they come back.
Hey Dave. I'm glad that burnt the board as you made a great video from it. The modification to cut through the carbonised board was quite neat considering the damage. Well done.
in fact , it should be clean up
Rd Tech difficult to totally clean off the carbon. Isolating the low resistance is the best you can do. Gets you out of trouble while you order another one if you care about the cosmetics.
@I have send him a new one . but make a slot is More thoroughly way
Glen, the location of those SMD fuses is horrible, if they blow you basically cannot access them to replace!
Andrey Kuznetsov if they blow, I'd move them to standard fuse holders external to the board.
Wouldn't a simple mod to resolve the problem be to fit a wire ended cap instead of the surface mount one. The wire ends would provide sufficient resilience to eliminate the stress being applied to the cap when the screw terminals are tightened.
Some ceramic capacitor manufacturers have MLCC SMD offerings which are much more resistant to PCB flexing and have a failure mode with a preference for failing open rather than being a short. Ex. www.avx.com/products/ceramic-capacitors/surface-mount/automotive-mlcc-with-flexiterm/
Brian Oldford
That was my immediate thought. I suspect that they just have those MLCCs in stock, saw that they could be soldered between the pins, and so used them.
An attempt to polish the product a bit by adding that capacitor ended up backfiring on them. At least they cared to try to improve the product.
Maybe the publicity and demonstration of their good customer relations will be a net positive.
But SMD caps are generally used because of their extremely low ESR. So if you add leads or out it further fro what you want to decouple, you're making it less efficient. Am I right?
If you keep the leads reasonably short and close to the board, the lead resistance is so low, its not measurable. Its not as if there are huge currents on the ceramic capacitor leads.
You know, that 20A fuse is shorted underneath.
Fuses are meant to be shorted.
?
Simon Tay think harder.
duh
So what you are saying is that it is now rated @30A
Amazing that a burnt PCB caused a short. Good repair for internal use equipment, customer would craps pants. Great video for repair folk!
Glad i just saw these videos. I bought one of these a few weeks back and didn't test it yet.
you can test it , if there is any problem, please contact me
I didn't test it yet but i might swap out the cap for a foil one to avoid any future issues, that board burn was bad! I never thought about carbonisation becoming conductive before. Nice work!
in fact, you can just remove it , that's ok, there is not any problem for normal working
Rd Tech
Hey I bought one couples of weeks ago and it has the same capacitor. . What should I do ?? To make it work without burning?
I see this all the time on laptop mainboards. Multilayer ceramic capacitors are sensitive to a lot of things: flex, mechanical shock, vibration (they're microphonic!) humidity, lots of stuff really. You need to be careful with your layout when you are using them in a high current power supply.
"The magic smoke escaped, so...it should still be a fully working power supply" is a sentence I never expected to hear :)
Thank you for making this. Very helpful!
Very good video, as always.
I'm going to remove that capacitor from my power supply right now.
Than you very much.
when I saw the "noise" on the scope I had a feeling it was suspiciously in sync to your speech...
I love the new channel logo animation! Subtle & pretty.
Good to see you back at it keep the videos coming thank you.
he should make a video to show repair
Of course, you meant to say, "that if you put two similar capacitors in series," you halve the capacitance not double it!
Brian John I think he meant when one capacitor shorts out.
I meant if you have two caps in series (half capacitance) then if one shorts out your capacitance will double.
Good points on PCB design with MLCC.
yes, it is not good place for that capacitor
That's some sweet trouble-shooting. Nice explanation and fix, thankyou very much!
@ Damien Wise
Hope you still like it
Good technical autopsy, mechanical and thermal stress,
Very educational, Dave. Many thanks.
hope you learn more
The lesson here is that you don't need to torque those PCB screw terminals like a Head Bolt. It takes surprisingly little to achieve zero resistance. Just beyond snug might be best. Just enough to keep from falling out. Rookie car mechanics are always breaking bolts.
I have a DPS5015 and also went black!!!!
Simply when I was testing a simple and tiny DC motor with 3V!!!
Does not even turn on anymore!
Any tips to repair it?! Glen?!
Excelent lesson! Thanks Dave!
DC output should be as clean as a cell battery, right? Right.
A ripple factor at the output so high and with many switching peaks at 200/300 KHz means that is a power supply with a quality that leaves much to be desired ...
Dealing with the failure of this device made for an interesting pair of videos. Old resistors were made up of carbon. The fire left a carbon deposit on the board has effectively created a resistor that was distributed over an area of the board instead of in a nice cylindrical package.
There is still a bit of carbon beside the one fuse on the top of the board. It might compromise the circuit safety should it ever blow from over current. The remaining carbon may still be providing a low resistance path between the two ends of the fuse. Two caps in series will cut the capacitance in half, not double it as you said. You could make a Fundamentals Friday video out of why cracks in MLCC caps cause them to fail shorted.
@Kevin Cozens
you are right , my dear friend
very good.
they should've gone with throughhole. stresses on the pins are much more forgiving than stress on the component.
If you're trying to measure output ripple and noise you need to use a high impedance probe with a ground ring connected directly across the output on the PCB. You can't use shity banana cables, you have a huge ground loop acting like an antenna. Also adding a high ESR electrolytic capacitor across the output (at the end of the wires!) won't help the ripple at all, it needs to be a specifically selected capacitor with the proper ESR and located very close to the switching inductor.
I have one of these modules with the case, not the exact same, but the input cap is gone, or relocated. Problem solved. It works great, I'm using it as a bench power supply and powering it from a computer PSU because of the high output current.
Very nice repair and explanation. I learned something.
@ Frank Gormanns
yes, it can show many things ...
CRACKING!!! I WAS RIGHT!!!!
Interesting video with great practical information about these multilayer capacitors and the conductive effect of a burned PCB.
On question though: you mention putting two capacitors in series as a solution to prevent shorting-out failures. However, in case one capacitor fails one would not notice that it failed (only less capacity), until the second capacitor also fails, leading to another flaming short-circuit situation. Wouldn't it be better to put a fuse in series instead of a second capacitor? Maybe even better to always add a fuse in one supply line, before the capacitor that goes across plus and minus?
The odds of two shorted caps is incredibly remote.
Clear. Thanks for your reply! I guess my poor understanding of the word "susceptible" led me to derive incorrect odds from your the statement at 15:40 ("These multi-layer capacitors are susceptible [...] to not only mechanical stresses [...], thermal stresses, they're susceptible to just a failure in manufacturing [...] infant mortality thing [...]").
Do I understand well that the odds for mechanical stress were in this case greatly enlarged by soldering the capacitor between the poles and that the other potential causes are much less likely to occur? I ask this because in my own projects I have often soldered an SMD cap close to, or even on a regulator and I wouldn't want that to cause a fire.
I now wonder how dangerous the placement of the caps is that I chose in projects such as in this video: ua-cam.com/video/K7Lv5FWTX9Y/v-deo.html
I know I am probably violating all rules of proper PCB layout in that video, but hope it isn't too dangerous!
@Maxint R&D
two them in series is not good idea, the best solution is to use a better one
@@rdtech9153 it's good to see you following the discussion. I just bought an DP20V021 because you worry about quality and the satisfaction of your customers.
@@ytrew9717 why you buy this old version, it is very old
Neat! I learned that these capacitors can fail like that when they have mechanical stress cracks in them.
@SysGhost
yes, it is normal
The environmental noise waveforms seemed to appear in time with your talking and the waveforms look suspiciously like audio.
Dave is a cyborg and his maker forgot to put suppression caps
^This made me laugh louder than it had any right to
Nice video and useful to understand the problems and fixing it more useful than working first time always learn something.
good
Charcoal is largely molecular carbon. Nice and conductive.
Was I seeing the wave on the scope jump as he talked?
Still gonna buy one of these when they are back for sale
@Max Bambusman
we have already solved the problem and updated that , don't worry . from that day, we begin to sell new version , and we did not stop to sell..
13:30
Of course the 22uF 200V won't do anything good for the noise, because it's ESR is so high compared to that of a small 100nF ceramic cap!
I would've removed the fuse, then remove all traces of carbonation, then solder the fuse back on.
It will remove all doubts as to any short circuit under the fuse.
Probably cutting off the corner with the terminals, then soldering wires to the proper places, adding an external fuse, then also moving the sense point to the output receptacles would be the best fix.
If you removed all traces of the carbon, you'd have one big hole where the fuse used to be.
How would two caps in parallel help? A short is a short.
Shorting ceramic caps is a known problem but not something I've experienced much despite the millions we use, quite unfortunate I'd say. AVX have a "flexicap" range so maybe the bigger brand technology is mitigating this problem.
Looks and sounds fine.
I think it's a bit more echoey than my other cam.
putting 20A fuses on tracks that go through a set of vias is height of optimism. And 2 fuses in parallel at that!
Hi Dave can you make a video about pcb design and track spacing . Would be interested to see if eg pwm, uart, i2c etc do some crosstalk and how close you can layout them without problems. I think measuring that would be interesting
The animation looks cool!
It's literally missing half the part of the fixing (soldering the sens wires)... and 95% is dave talking about some capacitance.
You think he didn't fix the sense tracks? You have little faith in him.
@@PunakiviAddikti no..we wanted to watch
Next week: Repairing electronics with a chain saw :D
Ive also experience problem on ceramic capacitor that shorts out the power supply and it burns the charging ic for the battery and one other component that seems to be an scr but i couldnt find a replacement parts here in Philippines smd is not that popular in here,we have very limited suppliers for smd component . So is it always the ceramoc capacitor that usually fail in smd component thanks Dave
Well Dave, what should I say? There are reasons for paying for a properly trained engineer with experience when designing products, whether its electronics or anything else. Today's market where "makers" think that they can design build and sell things leave everyone at risk of failure. This failure was mostly benign because you were attentive and understood what to do. But burning electronics can lead to the complete loss of a structure and lives. So this has to be classified as a very serious issue.
I'm sorry, but I have to correct you: a 20 A fuse MUST NOT trigger at 20 A - never. Depending on the standard is has to meet, it might trigger at 1.25*20A after 1h or something in that order of magnitude. Check on google for some current-time-curves, if you're interested in more details ;)
He showed a current-time fuse curve in the freaking video, dude. 7:25 And a 20A fuse run at 20A will eventually fatigue and blow under "normal" use. You don't run any components at 100% of their rated values if you want them to last. It isn't good engineering.
What is wrong with you?
Yes, he is showing a curve - thanks for telling me, but at least you definetely didn't undestand it.
Just in case you didn't know: This is a logarithmic plot, so if you look at the line for the 20A fuse, you'll see it is only specified to blow at 40A (or more) after 3 sec (or less).
The plot does NOT specify anything about 20A for 20A fuse. So if you - as I said - do some googleing, to find other curves, that specify all the operating range of a fuse, you will see, that no normal fuse will blow at it's rated current - ever.
This has nothing to do with good engineering, I'm just talking about device characteristics here.
There are even standards out there, that require, that a fuse MUST NOT BLOW for any current less than 1.3 times their rated current for several hours.
I usually like discussions, but please don't come up with some things that you "think" are true but instead do some research before you accuse the things I say.
I never said, that you should put a 20 A fuse in there. I never said you should always put a fuse in a product, that exactly matches the nominal current of the product. I get that fact, that they were not willing to put a 20 A fuse in there - it makes sense.
All I wanted to clear is the common miscconception, that a 20 A fuse blows at 20 A. This misconception is very common indeed and is just not true. If you have a 16A fuse at home in your fuse box, you can draw 20A "until the cows come home". This is what I wanted to get across.
Does that mean, you should put a 20 A fuse in 20 A device? No.
Using a wire wheel on the dremel should work well to clean away the burnt board....
the explanation is incomplete, it should be photographed one by one after that what to do after cutting the middle part?
*"short video"* *short video* *SHORT VIDEO* ?
Yeah, short video.
Haha.
It's a short removal video.
EEVblog I love those short videos
For Dave anything under 20 minutes is short.
3:48 "Burnt fiberglass --", erm, excuse my nitpickiness, but isn't glass mostly silicon dioxide? My best guess for the source of the carbon would be the hydrocarbon-based resins used to laminate the fiberglass layers together.
yes
Thank you mr nit-pick
If I'm not mistaken, fiberglass is a thermoset plastic with glass fibers in it and not pure glass.
fiberglass is a COMPOSITE, its not just glass fibre, hence those resins ARE fiberglass
I think the cap has been torn apart as you bent the board by pushing down the terminals while fastening them.
Just putting one of these together.... NO cap there by factory of course (just some Fuses)
One of the fuses is stillshorted by carbon. You could move them to the other side of the board, scratching away the solder resist on the terminal and inductor pad.
@
superdau
he use a knife to scratch, but he make a slot, it should be ok, too
If this PSU will have load with high short-circuit reverse current capabilities (high input capacitance or simply electro-chemical cells for example) this part will fail with explosion. As there is no safety features it can do same thing while catching a high voltage spike.
Its funny how they admitted that it has happened before, and now they have to fix it because it happened during a review. They didn't care that that had happened to customers in the past. I'm glad that it happened during the review, because if it didn't, they would not of fixed it and would be still selling it to anyone that would buy it. Luckily it happened during the review and Dave knew how to handle it. There are probably a lot of customers out there that had purchased this unit and might have been devastating to them and still not know there is a problem. Not sure how I feel about the company at this point. They knew there was a problem and continued to sell it. They were forced to speak up because of the review and were expecting to gain sales by paying someone to review there product. It blows my mind. They knew there was a problem, sold it anyway, not caring of the results, and they sent it to get reviewed. I also noticed, that Dave usually trashes items like this, and destroys everything about the design including the designer having ugly children or leads were loose or too small, or he smelled on the other end of the phone. There was a few things, that he was like "oh well", that he would of spent a great deal of time about how bad it was. That is what makes me think he was paid to review this product and also do 3 updates about it.