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- Опубліковано 28 вер 2018
- Today we will try to repair my bench power supply I destroyed a few weeks ago. And during this process, we have to learn how such a linear power supply works. Will I be successful?
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I built my own linear benchtop power supply based on a kit back in 1983 when I was bored and unemployed after graduating as a Mechanical Engineer. The kit had 30V output but low current limit at lower voltage because of the power dissipation. Read the data sheet and found alternative secondary tappings on the transformer in the box. Connected those and the original via a DPDT switch to get high and low voltage output, at maximum current.
What I learnt dabbling with electronics helped me get my first job and helped me design and to realize machines to make things easier in production on the metal fabrication shop floor. When the work got easier, quality improved ... Sometimes also the quantity.
Ahh, nothing quite like the feeling you get when you fix something! Great stuff
Thank you!
I soldered wires to a 3 pin header and put hook clips on the end, that goes into those trans testers as an adapter so you can test awkward parts. Sometimes you can even test in circuit. Also did one with logic probe clips on the end for other stuff.
Congratulations, nicely done. I bet your cat knew what was wrong but as cats are, she kept it to herself.
You are right, at least with the second part ;-)
My dogs are pretty much the same way ;)
Thanks a lot Sir! I have my target of building up my own linear power supply and you just showed the working operations of such a supply
Thank you for videoing this journey
You are welcome!
congrats to the successful repair and another helpful Video.
I love linear power supplies. My wife hought me a siglent one for xmas and i was blown away. I have a homemade one but there's no negative output. I have old wallwaets from music gear that output ac. I am getting an lcr meter tomorrow and will need no more test gear. Need being the key word haha.
Indeed, linear power supplies are excellent. And rare these days...
Very nice and interesting Andreas. Repair videos are always helpful and you learn something
Thank you! At least I learned something ;-)
There is no joy like fixing the equipment you broke by not being careful!... Awesome...
Thank you!
Many thanks Andreas, it was good to see your method.
You are welcome!
First off congratulations on the fix, great work!. It was great to see how the issue of heat is always handled in these things.
Thank you!
Thank you very much Andreas, I was hoping that you would fix that & show all of us. Now at least I know a little about Linear supply bench/lab type power supplies. Always PWM. is all I get to see.
You still find linear PSUs, but usually quite expensive.
Congratulations on a great success and fascinating video. I markup circuit diagrams with notes of replaced components as a reminder to myself for next time!
A good idea!
Very educational! Great video.
:-)
A vacuum de-solder tool is quite handy compared to a solder sucker and they appear sometimes on ebay. Great repair... (I have a PSU with a similar problem that I haven't got to looking at yet).... this will be very helpful. Thanks!
Congratulations for your success
Thank you!
Nice repair video :-)
Thanks for sharing :-)
Congratulations on fixing it. We all learned something new
I am always glad to read my videos help to learn something!
Thats what most Hobby engineers do. Repair and Learn. Great Work.
Thank you!
awesome episode , thank you so much I learned so much from it , I hope you keep making such fixing and principle of working episodes,
I have been wondering for so long why I hear a relay sound when I keep changing my power supply voltage now I know
thank you sooooo much
Thank you! So you have a nice power supply. Only the expensive ones have such relays ;-)
Good job Andreas :)
Useful video 👍 Excellent 👍
This is a common phenomenom on all power supplies. Without a diode on the output you will get back feeding of current of the device you are powering. For example, if you are charging a battery the battery will spin the fan on my hacked ATX power supply, but no damage like you see here. This repair should have been simpler because if the chip were at fault you would most likely see a different symptum, probabily just a non functioning channel. Most of the time, with this kind of over voltage type damage both the power transistor and the driver chip shorts out. Thanks for posting this repair.
You are right for charging batteries the "wrong way". I think this was not caused by back current (I had no burned traces). It was most probably an over voltage. Diodes at the output of precision power supplies are also problematic. GreatScott recently did a video about that.
I was pretty convinced that you were able to fix the power supply. Great job. The supply may be old school, it is defenately a nice piece of hardware that will last for many years. I build my power supply, the famous Elektor one, back in 1982/83 and although I used and misused it (as a battery charger...) it still performs excellent. I've always been fond of power supplies....
Another viewer also wrote he built his PSU in the 80s :-)
Many years ago I used to repair stuff. Fiddle as much as you but sooner or later I would get it (most times). Older stuff is fun.
You are right. And it is easier if only standard parts are destroyed.
Good video Andreas and a nice PS recovery. Sadly we all know this is likely to happen to everyone since not only everyone makes connection mistakes but also there is always the possibility of defects in our own pcb's soldering and the like. It simply happens. Many thing can go wrong and and the rule is ... what can go wrong will go wrong :) . That's why it is paramount to have a Schematic of the power supply as well as all the basic tools we use (Solder iron, multimeter and the like). And I also love Linear Power supplies.
And in addition, I have nice viewers who helped me to find the diagram. Much easier!
Awesome.. Thanks for sharing
You are welcome!
Lol , this is funny , just checked, forgot to close chrome, last video I was watching was your about WiFi modules....... , and got call for work. After 2 hours I am back and found I still playing videos from you , than I started with pressing back, back back back back and so on, and UA-cam decided to play only videos from you as I had autoplay on.
That was a nice experiment on how UA-cam works. And thank you for the many views with full playtime. Most of the viewers do not stay till the very end ;-)
Great work Andreas!
I was pretty sure you'll be able to repair it!
Nice idea to switch the voltages to keep low power disspation.
It is the first time i see a linear power supply with these feature.
But all my power supply are from kit or copied from magazines, not professional stuff. The maximum complication was the double secondary: one for power and load and the other for reference voltages ! Bye
Mine is probably also "semi-professional". I did not buy it new.
Congratulations! I'm currently working on a hybrid switching and linear PSU. This is, switching for 230 V to 3-50 V and then linear regulator for 0-47 V (due to the dropout) for reducing noise, at the same time it's more efficient and lighter. And of course, I'll put a TFT touch screen (OK, touch screen might be a bit too much).
I plan a similar thing (only up to 12 volts). Which linear regulator do you use?
@@AndreasSpiess Take a look at the LT3080. It's a really flexible chip for this kind of things. You can use them in parallel for good heat spreading and higher currents. I think Dave Jones used them in his mobile power supply. Internally it is simpler then a lm317. This makes it easier for voltage regulation and current limiting, by a microcontroller.
Andreas Spiess It’d be more appropriate to say “are going to use”. I haven’t even wound the isolation transformer for the SMPS part yet! (for which I also have to make a spool and Litz wire). Or maybe I should just buy an already made SMPS (the problem is that I already bought all the parts :/ ).And I still have to design and etch a few PCBs, solder the components, test it and program the MCU. I still have a long way to go.
what a truly great vid …….thanks!
You are welcome!
Thanks for such a great video. I had the same problem with “Votlcraft ps 3610” , mc1458n is not working and resistor 107 burnt, but transistors are ok and current control’s working
These are old devices but quite easy to repair :-)
Thanks for the video.... Ill build a fixed power supply for my application....
Fixed supplies are good for many applications. Variable ones usually have different applications. And you only need one ;-)
Spitze, super wieder was gelernt, die Relais habe ich auch immer gehört um ehrlich zu sein, lade ich immer mein ebike mit nem Labornetzteil, nach den neuen Erkenntnissen werde ich mir mal ein Schaltnetzteil besorgen. Im übrigen meinst du bei 14:10 sicher Ohm
Really interesting. Just yesterday, the day before I watched this, I was looking at power supplies and thought to myself, I wonder if there is a way to switch in different windings and to feed the DC side of the supply and here it is, exactly the same thought. I even wondered if anyone had used a variac to do it. Probably so.
I was also surprised there wasn't even a speck of dust inside that unit :)
Using taps was a common thing before we had switching regulators...
Good job! The easy way to test your power transistors is with your component tester!
You are right. My testers only have sockets. So it was easier this way...
i'm glad you repaired the benchtop ps, those chunky transformers are rare this days!
I assume because they are quite expensive and electronics parts are cheaper
I just picked up a faulty Agility E3646A dual rail supply, these things can get complicated! I will be doing a live stream next Sunday whilst I try to track down the fault.
I hope you will succeed! I do not watch UA-cam live sessions as they are usually too long for me.
Andreas Spiess - what I have started to do is record footage at the same time using my normal recording setup, and create a normal repair video too, so the live stream gets the chat and entire process, and the normal repair video is the concise version.
Your videos are good in the level of detail and explanation you use, a nice depth of knowledge is conveyed, I tend to forget to explain exactly what I am doing, for those that are in the early stages of learning.
bravo
:-)
*FULL BRIDGE RECTIFIER!*
Yes!
Replacing some parts and spending some time is a whole lot cheaper than buying a whole new unit :)
I have an old PSU I need to go through and give a good checking over. I think I need to replace the front varistor as the readings aren't stable. The unit was exposed to outside humidity (good 'ol Fl; >70% humidity on a "dry" day :P ), so it's probably toast.
Mine is generally in a good condition, even if it is old (I bought it "used"). So it was worth the effort. I hope you also will be successful!
Andreas. It said your video the other day was new. Im just seeing this now. Yt has been doing this to me lately.
This is a very old video. But the content is still ok.
Could you make a video about the esp-rfid project? I have some trouble setting it up
I have no plans for the moment.
Andreas Spiess Thanks for the reply! Anyone who made a video about it? Would like to try doing it without bricking my device
It is usually hard to brick a device by just flashing software.
Andreas Spiess I know, but having it on 220V and connecting an rc522 to it is pretty risky
Forgot to add: i have a sonoff and an esp8266, i would like to use the sonoff for the rc522 and the relay part if possible, but having an esp8266 connected to the rc522, and sending an mqtt message to the sonoff would be also cool
I knew you'd resurrect it!
And now you have spare parts on hand in case you blow something up again... ;)
And the know-how which one it is ;-)
I bought a linear power supply to actually hook up my audio equipment (and to do some other home testing). I just can't figure out how to hook up stuff because I don't want to blow anything. tho it has a black and a red circles on the back for positive and negative and im guessing i just unscrew and wrap the bare wire around the positive, and the negative around the negative and screw them back in and aslong as the voltage is set right it should work. Tho I want to make sure so i'm watching a BUNCH of videos until i see someone hook one up.
I would check it with a simple multimeter. Then you know.
Tolles Video sowie immer 👌🤙
Bist ein Top Elektroniker und deine Videos verfolge ich mit grosser Begeisterung🙋♂️
Nur eines nebenbei. Für diesen Voltcraft Bastlerstabi braucht ich kein Internet oder Forum. Da bin ich mit einem Diodentest weit schneller am Ziel🤦♂️🤦♂️🤦♂️.... weil viel mehr Technik als ein paar Transistoren und Dioden ist bei diesen nicht drinnen....
Grüsse aus Kärnten in Österreich
Ich war überrascht wie kompliziert es ist. Und es tut seinen Dienst seit vielen Jahren...
12:55 first curse in the history of this channel😂😂😂😂
I would not call this a "curse" ;-)
Clearly this type of power supply must have some control logic for switching the transformer secondary windings that includes hysteresis. I have wonder what effect switching the secondaries has on the output voltage. I guess some big inductors and capacitors BEFORE the regulator would take care of that.
It shows a hysteresis. The voltage is quite proportional to the angle of the potentiometers. But this is maybe because of the regulator which takes care of any switching effect.
nice. but, what kind catastrophic failure that triggered, that it took out so many key components like that. and it's strange that the cc did not kick in.
It was probably not current, it was over voltage...
so what was the 2nd transistor,a driver?
Yes.
So, why did it burn in the first place? Did your circuit inject current into the supply?
Most probably it was an overvoltage which killed these two transistors, not the current. Otherwise, we would find some burned traces.
👍👏
:-)
Prima. Es war nicht so einfach, wie bei meinem Netzteil, aber Du hast es geschafft. Alte Zahnbürsten sind nützlich, aber in der ESD Variante viel ungefährlicher für die gute Elektronik. Ich habe mir solche für wenig Geld aus China besorgt.
Ich wusste nicht dass es solche Zahnbürsten gibt. Muss mal sehen... Ja, es war nicht ganz einfach. Ich habe ja nicht die ganze Komplexität gezeigt und ich hatte einige Zeit bis ich die Schaltung einigermassen verstanden hatte.Die OpAmps werden nochmals aus einer andern Sekundärwindung versorgt, vermutlich weil ich die beiden Teile in Serie schalten kann und dann eine relativ hohe Spannung bekomme... Und dass es beide Transistoren gleichzeitig tötet war auch überraschend.
If you don't use the brush dry, you don't have to worry about ESD safety. Nylon is slightly triboelectric but when wet, the lost ions have nowhere to go but right back.
The ESD brushes come for cheap from China. Probably not more expensive than a decent toothbrush :-) So, why risk it?
Linear PSU was very interesting , pity the repair video was all over the place and choppy. Second transistor ? Testing the LM48 ? Not your normal style :)
Sorry about that. I thought, testing an optocoupler is not interesting. I only created a 10x amplifier and it worked. The second transistor was obviously dead because, after changing the first one, the PSU still had the same error..
Doesn’t it need to be recalibrated after the repair? Also I noticed a significant voltage jump when changing the voltage around 15-20 volts is that normally with liner power supply?
The potentiometers have no values written to the case. The voltage is only read at the display. So nothing has to be done in this case.
Typical cheap single turn POTs do that, that is the reason for the "Fine control" so you can get near the voltage you want then dial it in with the Fine Control. Higher end supplies use 10 turn / multi turn POTs.
Something is still different from the A channel. I'd be suspicious of the v/c regulation on the B channel. Something else is likely out of spec but not dead maybe some other resistors got smoked and are no longer at their nominal value. The good new is you have a working channel to hunt down what changed. Maybe poke it with a rapidly changing load like 2 power resistors one with a switch or a programmable load and scope its response and compare it with the A channel and compare its transient behavior is when it switches transformer taps. I'm not convinced the 43 volts doesn't come with a down side :) As always a good video.
Why do You get a higher max. Voltage after the repair?
I'm betting the Transistors had something to do with it. Probably uses a lower base current to switch the Transistor on. If it was me I would compare it to Channel one and recalibrate Channel two to match the Output of Channel one.
I do not know. But in the end, I used the trim potentiometer to get it to the "normal" level.
Can someone send me an user manual (in english) for this model? The "overload" led is always on on mine, and i have no clue wtf is that.
I do not have one :-(
Nice video as always. One comment, on minute 7:31 you show an equation to calculate the power which is wrong. You have 50V-5V equal to the power calculation but its not the same units, you missed the multiplication with the current
Another miss is at 9:29 were you do voltage squared and 60^2 is 3600 and not as is shown
7:31 seems to be ok for me. I multiply 45Vx3A =135 W
9:29: you are right.
@@AndreasSpiess on 7:31 you wrote P=50V-5V=... you have to write P=(50V-5V)*3A=...
i reallly should fix my bench supply, against the warnings i used it to charge some nimh batteries, then the power went off and the big battery pack fed voltage back into the supply, it has no protection against that... known bug. but it is from 1960's and until now was all original! (farnell l30b)
GreatScott! just had the same problem - ua-cam.com/video/7Tk5ghH_U2s/v-deo.html
Nice rig! And in 1960 the engineers were also more cautious because the equipment was very expensive!
Good job, most times a schematic will not be available.
Then it is harder...
13:50 maybe coil feedback killed it?
Yes, you are right!
Current regulator? Me thinks at start. Check parts aroud it too.
Negative and positive feedback loop love it.
Did you have a mica spacer as well as heat paste?
There is an isolator to electrically isolate the transistor, yes.
The u in circuit is silent
As a german speaking person, you would pronounce it like "Sörkit"
Checking the resistance with a meter is always a good idea of course, but you should be old enough to remember the incredibly racist phrases that used to be taught for remembering the color codes! :-D Or maybe Switzerland didn't have those. But anyway, you never forget them...
I do not know the phrases and was ok with the old (few) values (and gold or silver at the end). So I knew at least where to start. These days with the small parts, the 5 stripes and many more values, I gave up ;-)
I don't recall a racist one? We learned bad boys rape our young girls but violet gives willingly.
What I learned was virtually identical to what you learned, but it was racist as well as sexist. But it must have been a very effective teaching tool because a few minutes later everyone in the shop class remembered the color code, and I still use the mnemonic 45 years later. If we were just asked to memorize the color code, I would still be looking it up every time I needed to use it...
Ah. Googled it, there are a ton of stupid PC correct ones listed that are essentially random words.. completely forgettable :) I guess it just made sense in my head the 0 would be lack of color (black) to keep 0 and 1 straight. But yeah the humerus one is still easy to recall decades later. I did just lean the sliver and gold as multipliers not just tolerance bands though.
Yeah, I still remember learning this like it was five minutes ago. The mnemonic was so insensitive to multiple groups that everyone in the electronics shop class (and there were some complete zeros) learned the color code in record time, and most probably still remember it, whether they have been using it or not. That's the power of outrageous humor... Aside from the first word, rape was sometimes replaced by ride, which might have made the mnemonic even more memorable! ;-)
V^2 = 60^2 = 3600!
You are right. This is probably why it was so black!
Is it just me or its a youtube thing that makes this video stuttery?
I do not know. Nobody complained so far. And this is a very old video.