VoltLog #8 - Kit Assembly 0-30V 0-3A Adjustable Linear Bench Power Supply

[@tektech1065]

Thanks for the video, and troubleshooting your circuit. It works really great. I paid $4.50 shipped from Aliexpress. I love the way CC works from 7 mA and up. And CV works from zero Volts. A 5-turn or 10-turn pots ($1 each on ebay or aliexpress) work better than single turn. If anyone has problems, here are some tips: 1. Make sure the Zener diodes are marked 5.1V - use magnifying glass to read. If you put the look-alike 4148 instead of Zener: you will fry the OP amps because you will hit them with unlimited voltage. TL081 cost $1 for 10pcs shipped, if you need replacements. 2. Make sure to place the two small transistors in proper places: one is PNP and the other NPN - you can't interchange them. 3. Measure each resistor before soldering instead or relying on barcodes: the blue background paint makes them hard to distinguish. 4. The medium power transistor on small heatsink may look the same as the 7824: don't mix these up. 5. In my kit the small capacitors 100pF thru 220nF were very inaccurate in values, so I used caps recycled from old TV board instead.

[@voltlog]

awesome tips, thanks!

[@JohnWick-pz5vp]

I assembled this power supply and supplied the AC input via 12*2 3A (Centertapped Transformer) but unfortunately there was no correct output at the output terminals; it's almost 0.3V DC. But when I checked the 82 ohms resistor which is near to the reverse diode capacitor multiplier (17.36 in this video) gets much hot. I checked all the directions and components but still it's not working. Can someone help me to solve this issue?

[@tektech1065]

@@JohnWick-pz5vp When you pause video on the diagram 16:59 you can see that the 82 Ohm (R2) is in series with 47 uF (C2) capacitor, so this should not get hot at 60 Hz. Perhaps the capacitor 47 uF (C2) got shorted? Replace it and see what happens. Also, the center tap of the transformer has no meaning in this circuit. The 3-screw input terminal has the center screw not connected to anything. Measure the AC Voltage on the two outside pins: it should be around 24 Volts AC, but the circuit will work fine from 8 Volts AC and up.

[@englishrupe01]

@@JohnWick-pz5vp Yes that resistor does get hot...but it works OK anyway. You probably have a bad TL081. Either order more (I got 50 for under $10 from a US seller) or use the UA741 as someone else has suggested. Oh and buy some sockets for the opamps, so you can change them easily if you need to! I ALWAYS use them now. Be very careful desoldering the opamps or you will lose the traces on the board.

[@ajaybnl]

I built same aliexpress Board. Worked with ac transformer, after some time fried tl081 on the right. I did not used diode in place of zener. What could be the reason of fried op amp?

[@adamsucksatyt]

Power supply kit FINISHED!!!! IT'S WORKING BEAUTIFULLY!!!! SO HAPPY THAT I FINISHED IT AND IT WORKS!!!!

[@Laziter73]

I ordered this kit from eBay, assembled it and I'm happy. I used a rewound microwave-oven transformer, all is just perfect for my use (not being one to use micro-volts in daily use). The idea of using multiturn pots to adjust voltage and current is just great, it makes all the difference :)

[@davespiller8723]

Thanks for the nice video. My kit came with no Schematic and thanks for showing it in your KZbin. I thought the LED was a power on LED and forgot to put a current limit diode in series when testing the polarity to remotely connecting the leds, needless to say it blew out when I tested it. I guess I will replace it with a white LED and use the fan power connection to light a led on the front power pannel. Is the circuit board mounted led light only lit when it is in constent current limit ? Thanks in advance for this primitve question as to the operation of the LED purpose.

[@spacial2]

Thanks. I made exactly the same mistake testing mine using two 12V sealed lead acid batteries. There is a set up procedure, if I recall correctly, putting the current pot at max and the volt pot at min. Then adjusting the trimmer to get a 0V output.

[@johnmellor6065]

i bought the kit and have built it b ut found the lack of information was weak the i found your site and you filled in all the blanks so all i could do was subscribe great video great info it made such a difference

[@johnrudd9550]

John, , look up Practical Electronics October 1978, it contains the original design…

[@crocellian2972]

I forgot. Good job on trouble shooting. It is your most important tool. Rule one, do nothing but think. Rule two, measure voltage. You would have spotted the clamp right away. Young man, I don't know where you are in your journey, mine is almost over. But you have the makings of a great engineer, teacher, company builder, you name it. You are a star. Shine.

[@voltlog]

thank you!

[@adamsucksatyt]

I sorted and labeled all the resistors, so tomorrow it will be easy to do Also I learned how to read tantalum capacitors (yellow bits) The first 2 numbers are just numbers, BUT the third one is the multiplier (how many extra zeros) Example: 304 30 4 30 +4 zeros 300000 pF 300 nF 0.3 uF

[@mushtaqobaray7529]

Liked your video. Can you send me a link to the Circuit explanation, as do not understand it. Thanks

[@decem_unosquattro9538]

2:30 one hung lo brand? I never heard of that brand dude. 🤔

[@zooky443]

I want to thank you. I built the same kit and had the exact same problem as you. I was testing it with DC and did conclude that I wasn't getting my negative rail but assumed there was a fault with that part of the circuit. Found the same schematic as you on the internet. One thing to remember. If you rectify 24 VAC it gives you about 34 VDC (VacX1.414=Vdc, this applies to a fullwave bridge only). Hence the first filter cap is rated at 50 volts and should also be greater than 3300uf to reduce ripple when drawing higher currents.

[@voltlog]

zooky443 I'm glad my story helped.

[@m-techno8352]

Is there short protection? If short, are led is on? Because i see if power suplly on, led is off.

[@johnarmstrong3782]

I very much enjoyed the video. I bought one and built it. It's fine but had to add a large fan cooled heat sink to the mosfet to run it anywhere near 3amps. Also the rectifier diodes get too hot to touch?! I don't know whether my 24v ac supply is ok because it's a square wave and not a sine wave?

[@informediatech-bruno5766]

man were you plug the 24 volt it says on the pcb AC24V it should be there for a reason i made the same mistake now i had to ordet a transformer and wait another 30 days coz my main power supply cost 1000 euros and its burned out im waiting th pcb to fix it

[@davespiller8723]

I found the circuit description link under show more and answered my own question. Again thanks for the video and the circuit description and schematic.

[@FranciscoRamos-du4rt]

Hello, is it possible to increase the output intensity from 3 to 5 amps? By lowering the Rs value? Thanks

[@ProgrammerEA]

Thanks for great video - i was looking three hours for where is a problem...turned problem at the DC...

I can use a transformer with output 20V AC?

[@ddistrbd1]

I hope you read this message and can help me out, as a total novice I decided to assemble this power supply on my own, I followed all the steps watching a few videos on this very same PS, my problem is similar to yours B4 the fix, I only get one output of 14.6Vdc with no chane at all, turning the potentiometers and adjusting the brass screw does not change my output, I am using a 24V, 2A transformer for my input power source, if we make a big assumption that all components were soldered correctly, where do you think the issue with the no-change output is, please help if you could.

[@rofeiga789]

Nice video but i m not getting more than 9v op what maybe the possible faults

[@zaheerkhan584]

Sir what will be the voltage at pin 7and4 of op ic no 1 2 and 3

[@mr.moonface4784]

Is a way to add a 12-24V 7Ah baterry to work as a backup/portable supply? From what I heard this model works only with AC-DC and not DC-DC wick is odd

[@guillaumelombard7210]

Got mine all soldered. The voltage works fine but when I turn it on the current is saturated to the max. I v checked for short circuit, can't find any. There is no load but the current limiter is on. Any idea?

[@spike5552]

Hi all, i have the same kit and i cannot modify the amps any more it only shows 2mA, i switched the potentiometers and they work, and the power supply was working fine until last week, when i powered on to charge a 18650 cell and i noticed that it only charge with 2mA 😢, what do i have to check ???

[@peterwebster3076]

hi there buddy I have this kit to build also but can you tell me what difference it would make to the kit by replacing the standard 10k pots with 2 5k 1oturn pots I look forward to your reply peter

[@voltlog]

usually you don't go below 10K with adjustment pots. It should still work but I have no idea if it's going to influence your circuit in any way.

[@khangowhar]

nicely assembled and soldered. you beautifully diagnosed the problem of DC instead of AC. Now i have some questions about this kit and i hope you will answer: 1/ what can i do to increase its current output only/ do i have to use two kits, if yes, how to connect them? where on the pcb could i connect amp and voltmeter and its specifications. can i use fine and coarse adjustments or should i use 10k 10turn pots.- eagerly waiting for your reply?

[@voltlog]

+gowhar khan Thanks! You cannot increase the output current by using two power supplies you will run into problems, voltage sources should not be paralleled. The voltmeter should be connected to the output terminals and the ammeter in series with the output terminals. I would recommend using a 10 turn pot, it's nicer. Also there is a really long thread full o information and possible improvements to this power supply, you should read it. Here is a link voltlog.com/y/bmdio

[@denzilcypret742]

Thank you for another well done and informative video. I have just finished building the kit and have met a problem that my very limited knowledge can't solve. I did not plan to buy a 24v transformer as I already had an 8.5 amp Variac, which seems to me would work just as well and still be available for other uses. But I may be wrong---my Variac has 2 output wires--hot and neutral--while the board shows connections for 3 wires and I am completely stumped on how to proceed! Can you or anyone help me out with this mess? Appreciate any and all advice or assistance! Thank you all!

[@Mtaalas]

If you're doing trough hole soldering, you don't need much flux (other than the one already in the soldering wire, you have rosin core solder now don't you?) on other than the largest component leads if your technique is correct, and the correct is: * Keep your soldering iron tip clean at all times (don't use sponges, they suck. Use metal braid tip cleaners) * Remember to have your soldering iron tip covered in fresh solder once in a while, makes for better thermal contact. * Remember to put the tip so, that it heats BOTH the component lead and the pad which you're soldering. * After a second or two of heating them up, apply the solder from the _opposite side_ of the component lead, not to the soldering iron. You're trying to solder the component lead to the pad, not the iron to the component lead. * And if you put the soldering iron away for a moment, remember to clean it well and add a fresh coat of solder to the tip to protect it from oxidizing. And you're all set.

[@voltlog]

Thank you for sharing the technique with us. I am using the exact same technique as described in your comment. However I have to disagree on the part where you say "you don't need much flux", extra flux is always helpful even though I am using solder wire with flux core. It just makes your life easier, why should I stick with just the flux I get inside the solder wire? that's not enough. Sometimes the core melts on the current joint more than it should and to your next joint you are left with only bare solder. The thing that gets you most of the time during soldering is oxidization of the solder on the tip or the tip itself and flux together with regularly cleaning the tip is a perfect solution for that. I have to conclude though, this is a rather "personal" subject as everyone does it their way, and everyone has their own sweet spot for how it should be done.

[@Mtaalas]

True, I usually use flux when I get a failed bead to touch it up. Saves time and flux. Since most connections are easily done without extra flux.VoltLog

[@Spark-Hole]

Mtaalas ,There use to be copper wire coat with silver for easy solder as time pass they change from copper to brass. now some Electronic parts from china use steel wire coat with may be nikle. Part from china are very difficult to solder that why I understand he use too much flux. Too much flux quickly ruin your platinum coating on soldering tip. I always avoid buying part from china.

[@bloguetronica]

A bit of added flux always helps. I normally do my solder junctions in less than 2 seconds, with a very hot iron (380ºC) to improve wettability. The flux from the solder wire might not be enough. It is preferable to err on the side of caution and clean the excess later. As long as you don't use conductive or acid flux, you'll be fine.

[@cagcos]

Hi. Thanks for the great video. Could you help identify the function of the pot on the lower right hand side of the board? Many thanks in advance

[@voltlog]

+Cagri Coskun If I remember correctly that is the 0V adjust pot.

[@cagcos]

+VoltLog thanks

[@decem_unosquattro9538]

17:24 I'm a bit surprised that you plugged DC into the input? Doesn't it say on the PCB? Thats what those shotky diodes are for. Its a full bridge rectifier (changes AC to DC) the transformer lowers the voltage from 240 to 24 volts. Anyway all good. Its working. Yaah!😂👍🏻

[@johnkg702]

Good day sir I have assembled the kit but not working . The output voltage not going above 0.2 v one tl082 if is getting Hot also (u2) . I have checked all connections and all components are correctly placed Pls help to find problem

[@englishrupe01]

That is definitely a bad TL081. I advise anybody assembling these to fit the TL081's in a socket first....otherwise it is very difficult to remove them later....and since they are pretty much at their limit anyway, it pays to have a few spares on hand. I bought 50 for around $5 i think....and the sockets are very cheap too.

[@Argonautica]

I made three of these kits and one was completely duff. Same symptoms as you. There are a fake or low spec TL081's out there, they have a 'V' type logo on them, I bought 5 of them to replace the hot one. Should have got genuine TI chips. None of them worked. If you get the circuit diagram and assemble U1, D8 , R4, R6, R5, P1 with DC anywhere over 15V you will get about 10.2V at U1 pin 6 and 5.1V at pins 2 and 3. U1 works as a voltage reference and the voltages I listed will be present for any DC supply voltage above about 12V. The TL081's in my duff kit and the 5 I bought off eBay did not work in this circuit, the output voltage on pin 6 was stubbornly 0V. I made a circuit in LTSpice XVIII and no matter what values of R4-R6 I chose I could not get 0V on pin 6, it worked as theory would suggest and as per the good good boards. This and the two good boards showed me where to look, having eliminated everything else I concluded the TL081 was not working as it should. In addition pin 8 was not NC, it was at Vcc. If you short pin 8 to Gnd the chip dies. I dropped in 741's instead of TL081, they are pin for pin compatible, and it worked. I put sockets on all IC's. Blown also was U2. R1 and R2 run hot to touch, they need to 1W I suspect. I replaced all TL081's on the duff board with 741's. The good boards have genuine TI chips. This solution took a long time to figure out.

[@maximelalonde2214]

Hi got a problem whit il I keep burning out the D1047 ac is god oamp is good all part are in right side . good solder . just stuck got some clus?

[@pier-dante]

Hello everyone: This circuit is quite good but the power transformer should not exceed 20V. The DC voltage in the supply (+ Vdc, -Vdc) in the operational ones when setting the 24V voltage exceeds the maximum values for which the manufacturer designed it. The maximum data sheet voltage says + Vcc - (- Vcc) = 36V, recommended 30V. It may work well for a while and then the operational ones will burn.

[@ajaybnl]

Exactly why i tested 12-0-12 transformer gives 40v on the caps. My Opamp Fried after some time. We should use 9-0-9 transformer.

[@adamsucksatyt]

@@ajaybnl OMG I JUST FOUND AN 18V 40W TRANSFORMER THAT CAN SUPPLY 2.25A max. (from a broken boombox) I only need ~ 3A up to 12V, not more :) So I'm GOOD TO GO!

[@adamsucksatyt]

#VoltLog my power supply kit can't limit current below 165mA.... I built everything using your schematic diagram.... Did I do something wrong? Or is it because my transformer gives out 25.6V RMS?

[@satfox]

Hi.Very nice video.I would like to ask for a litle help.I got the same pcb six months now and it was working properly and i am very satisfied with it.But two days ago a small circuit contact create a problem.The problem is that i can not regulate the out put voltage.It comes out 30 volts wich is the same input voltage.What component has been defected?I am total newbie and thats why i ask for help.Can you leed me what to check so i can find the problem?Thank you very much.

[@Unordung]

Great advise!

[@rushabhupadhyaya8752]

This is for 1 ph voltage ?

[@mindelgadore5380]

Another concern is about the resistors R2 (82R) and R3 (220R). They heats too much. Is the same on your boards?

[@KF-bj3ce]

Very good and precise description of this project including the analytical testing and fault finding. Thank you this has help me significantly. I am thinking whether one could add another stage to the output Transistor T4 of this power supply ( Say a pair of Transistors in parallel with resister to emitter of T4 ) to boost the current rating of the output.

[@sylvainlazare1114]

Input should be AC 24V however I have a transformer whose secondary delivers 29 V. Do you think that it could be OK for this board ? or is there any other means to adapt the AC input to 24 V. Thank you in advance for your reply. And congratulation for your nice video and tutorials.

[@proxymilian]

+Sylvain LAZARE I don't recommend using that transformer. When rectified the voltage could exceed 40V and the power supply components are not rated for that.

[@donaldfilbert4832]

Great video. I have one question. What does the trimmer pot do ??

[@voltlog]

the trim pot is for 0V adjustment.

[@donaldfilbert4832]

Got it !!! Thanks !! {:>)

[@adamsucksatyt]

@@voltlog mine is right at 0 volts right out of the factory

[@GeorgeTsiros]

Have you tested the power supply? Did you check its output with a scope, to see if it behaves correctly?

[@voltlog]

+George Tsiros No, I haven't. I plan on mounting this thing inside a case soon and I will probably do some tests when it's finished. Do you have reasons to believe it would not behave correctly ?

[@GeorgeTsiros]

+VoltLog Yes. Check tl081 supply rails in the circuit and from the datasheet. Do me a favor, slap a sink on that 3055 and a 24v secondary transformer and test the circuit's behavior when the current setting is very close to the current through the load.

[@GeorgeTsiros]

+VoltLog Also check for oscillations and ripple voltage as well.

[@anjayv8347]

volt log can explain how the short protection on this psu works, and does the 100k multi turn pot take part on protecting the psu from shorts?

[@DeeegerD]

+Anjay V Reading the manual there is no mention of short circuit or reverse polarity protection? Of course, it's not a detailed manual so?

[@Chrisjan]

Where is the 7824 regulator on your circuit diagram?

[@MixedGears]

I assembled this kit and it looked like it worked ok. But when I was assembling the circuit in an enclosure I accidentally shorted the negative rail to the transistor's cooler 2SD882 . After a big spark, it still could regulate voltage and limit small currents. Then I go with a stronger load car lamp and big spark on the output. No more regulation. I think I killed some components :/ Is this kit any good? is it worth fixing it or I rather replace the whole circuit with a switch mode buck converter with current limiting?

[@englishrupe01]

Just get another kit off ebay....for $4.50 how could you go wrong?

[@rahulkushwaha1984]

Op-amps are heating a lot... And later on getting damaged without any load connected... What should I do? Btw I made this circuit on a breadboard and got the output too... The only problem I'm having is heating up of opa.

[@coolgamer1989]

according you said about in the video, there´s no manner of make the power supply work then? happen the same thing you did using a 20 VDC power supply. its just no way to reverse the opams supply?

[@juliusvalentinas]

is this the only linear psu worth looking at ? cant find any other kits, or built ones.

[@voltlog]

the only one I know of.

[@rashel1262]

Hello What does the 0.47ohm ceramic resistor used for ? Is it a current shunt like you said before you had the scheme?

[@voltlog]

yes

[@hammadhassan9409]

Can i use digital potentiometer of 10k in place of mechanical potentiometer

[@jaskiratsinghubhi390]

Hi, I was wondering about what power of transformer should I use. I know this requires maximum of 3 amps of current. I found a 24 vac 40 VA transformer for reasonable price at local store. Is it going to be okay? I don't think the power supply will be able to provide 3 amps at 30 volts with it. Please let me know what you think.

[@voltlog]

that's a 1.66A rated transformer

[@jaskiratsinghubhi390]

Thank you for replying! I have couple of stepper motors that I want to run at 24 volts. Does that mean that I can have only 1.66A total current from the power supply? I mean 24 vac must be rms value so the peak value would be 1.414*24 i.e. 34v. Now we are stepping it down to 24 volts so the final output will be able to provide more than 1.66A dc.

[@adamsucksatyt]

I'm using a 24V 48W transformer, since I don't need 3A across the voltage range But still 16 volts and below - 3A

[@Laztef198]

Hi, how can I solve that problem you had? the output voltage remains at 0.34v and for more that turn the voltage potentiometer does not rise or fall on the output. It should be noted that the power I give is 24v 3a AC. Thanks in advance

[@4EVERGR]

Matias Cueto Hello friend. Have you solved this problem, because I have same issue with 24v 4a AC transformer. Getting only 0.614v at output. Thanks.

[@hesuscruz3672]

Ola amigos I got same issue.til now searching for answer

[@Aneesh-bd9es]

Sir I assembled the circuit and double check each component,all are ok,and I connected a 0 24v 5amp transformer at the input,but didn't get the out put like the video,opamp get hot,there is. No negative voltage on ic pin 4,I don't know why,pls help

[@englishrupe01]

Probably a bad TL081...swap them out after putting them in sockets.

[@adamsucksatyt]

#englishrupe01 No negative voltage on IC pin 4 means there is possibly something wrong with the voltage inverter for the op amps Maybe a faulty component? ------------------------------------------------------ :( Your PC ran into a problem that it couldn't handle, and it needs to restart. We're just collecting some error info, and then we'll restart for you. (-1% complete) If you'd like to know more, you can search online later for this error: ADAM_SK_EN_FATAL_ERROR

[@cayala75]

Hello all, I bought the same kit and facing the same problem when i applied 19Vdc (laptop charger) to AC input. but, I solved the problem, building a Inverter circuit based on 555. The additional board has a 7808 Regulator (+8V) and inverter polarity circuit based on 555, this give me ~ -5.0V, then I apply it to the anode of D7 (Zener 5.1V) to polarizate to OPAM. and. PROBLEM SOLVED the KIT work well !!!!!!!

[@arpitawebsite6981]

hi can I use a 24v 5a transformer for the above circuit, since i have it with me. thanks

[@ConsertandoTudo]

yes you can, but you should not. . The opamps have a maximum voltage of 30v. After filter, a voltage of almost 34 volts apear. Under load, I'm sure it is not a issue, but I let mine powered on over night with no load and burn the opamps. This power supply shoud be ratated maximum to use with a 20v transformer. 12 0 12 or 24 0 is too much for this supply.

[@FeriBeke]

Hi, does it have a protection against shorts? Description states, that it have, but one customer reviewed the product/purchase on banggood, and says, it has not, and that he learned this the hard way... thanks

[@voltlog]

Feri Beke not really short circuit protection but it has CC mode which will limit current based on your setting. I haven't had issues with this power supply and I've short circuited the output many times.

[@MrBobWareham]

I loved the video very informative and helpful I have ordered one from Ebay so I was wondering the board size if you happen to know the measurements I would be most grateful and thank you again for the schematic so another copy from China they just copy everything. Thanks Bob

[@mindelgadore5380]

Hi everybody. I bought this kit from AliExpress and the 3 IC came without any label. It suppossed to be TL081. Because the PS did not work I replace the 3 "black" IC by LM741 and board regulates voltage without load. Still an issue with the current regulation when 10ohm load is connected. No more than 0,3A is possible to reach. Up to that current, the led lights and current limiting starts. Could somebody help on this issue?

[@Sandokans]

Salut. Din câte am înțeles, schema asta nu are, protecție la scurt circuit, ceea ce mi se pare un mare minus. Poți să-mi spui dacă i se poate adapta un circuit sau ce modificare i se poate face, pentru asta!? Mersi

[@rantalbott6963]

Thanks *very* much for the warning about the negative rail. I just got the kit, and was planning to plug in different DC supplies at the input to reduce heat dissipation from the output transistor (e.g., a 9-10V if I need a 5V or so output, a 24V if I need something around 15V, etc). I would have gotten caught in the same trap you did. Is your schematic available for download? The one at electronics-lab.com is helpful, but it's nicer to have the component values on the drawing for understanding the circuit. Thanks again.

[@Impetuss]

You can just screenshot the video for schematic

[@Impetuss]

Here: imgur.com/a/3N58n9k To do it yourself, PRT SCN top right of keyboard, then CTRL + V into paint and save as PNG

[@cojeiguenhertranka8672]

Hi, if I conect 24 Vdc directly to the A.C. input of the rectifier bridge, ¿will it work? Thaks a lot.

[@voltlog]

COJEIGUEN HERTRANKA It will not work with DC voltage. As I've explained in the video it needs AC voltage for proper operation.

[@SidneyCritic]

Would it work with less than a 24V AC transformer. I only need 12V, and have a transformer out of a ATX PS - I think it's 12V (EI-40C) -. Would that be ok, or does it have to be 24V.

[@voltlog]

+SidneyCritic ComedyHound yes it will work with 12V AC.

[@SidneyCritic]

+VoltLog Great, that will save me some money. $15 for the kit, and $40 for 24V AC transformer, wouldn't make it cheap. I can't find the specs on the EI-40c transformer, so will have to test it, but there is also something in the PS that looks like toroid. I'll have to investigate. Thanks

[@voltlog]

+SidneyCritic ComedyHound Here in Romania, a 24V 2A toroidal transformer is about $15 and a used one could probably be purchased for less. Wherever you are from I am sure a cheaper transformer can be found. ATX PSU do not contain toroidal transformers. And the other transformers contained in an ATX PSU are most likely not suited for this job.

[@SidneyCritic]

+VoltLog I just found one at $18 on eBay, but when you add the circuit($15) and a volt/amp panel meter($8) it comes out at $41, so I was trying to cut costs in half with the ATX PS parts. I've got a failed ATX PS with lots of transformers, and the biggest is a EI-40c, but I can't find exact specs. Maybe this www.kondzio.info/images/artykuly/2015/transformator-impulsowy/EI-33-datasheet.pdf chipsen.en.made-in-china.com/product/IBZJxAPdgnWk/China-EI40-Current-transformer-specification.html Here are some pics www.mediafire.com/convkey/5cfc/snsaot1xhjknz3b6g.jpg www.mediafire.com/convkey/c141/4uva5mjt899iyto6g.jpg www.mediafire.com/convkey/edff/z66lnkp4g9f05jd6g.jpg The gutted ATX case has a 12V fan, 240V connections, switch, and what I think is a filter inside - cap and inductor -, so it's ready to populate. Any advice would be appreciated. Thanks

[@voltlog]

+SidneyCritic ComedyHound The PSU KIT is $10 goo.gl/3r5YKl , you will also need a heatsink.

[@mehedihasanasif4879]

can i use two 2sc5200 in parallel instead of d1047?

[@Aneesh-bd9es]

I order the same product.after I assembled it,it won't work opamp is hot I changed all opamp then all is good.but when I connected a 2amp load on output led light up and then out vollt become 0v,I tested all component.I see ,47 r resistor is open and also 1047 is short, What is the max out put. When I connected this load the heat become a little bit hot.I provide a good heatsink and a fan.I don't think it provide 3 amp output and also no over current protection also,if there is a over current protection 1047 will not be short.

[@englishrupe01]

Did you set the CC by shorting the leads first? It does work...at least on my kit.

[@Luftbubblan]

Probably a stupid question but i have a simular product that ive just finnished and want to test it out. I dont have a power supply with the correct values doe so my question is, could i run a product like this with lower voltage just to try the circuit out? Needed: 30v 2A Closest ive got: 24V 2.5A Will it break or just not start?

[@voltlog]

it will work at that voltage as long as it's AC.

[@Luftbubblan]

Tyvm :D Will try it out tonight then.

[@danielnight5717]

Hello Can I use different voltage regulator to fan like LM7212CV. Is this kit support 18V transformer ?

[@englishrupe01]

Yes, i believe you can

[@MrAnimeAmv1]

hey i have a Problem, i have the same board and used an led plug (24v) for the input but it doesnt work. when i measure the input voltage it was 31v (idk why) und the output voltage was -0,59v. is my board fried or does anyone have an idea what could be the problem? thanks

[@nef003]

Wow, I bought this kit - and I just wish i had your understanding of reverse engineering. That way i would just make one myself. :) It seems you are capable of making anything.

[@juliusvalentinas]

Take LM338K and build linear voltage or current supply 5A supply with few components. If this kit would be 10A or so then it would be worth it. Any mods with increased power? Any digital versions? It's year 2018.

[@englishrupe01]

You don't think this kit is worth it for $4.50?

Do you recommend buying?

[@adamsucksatyt]

Power supply kit almost finished Tomorrow I will buy a 7812 so I can use a 12 V fan which is built in to the box and also the DIP8 sockets for the op-amps.

[@DeeegerD]

Thanks for the video - just purchased one prior to watching this - looks good and I was wondering about the power transistor heat sink - maybe the aluminum case will be enough - I will have to test that (heat vs current, etc...). Should be a fun kit. Oh yeah, definitely want 10 turn pots as well.

[@voltlog]

Digger D right, you would have to test dissipated power vs resulting temp. It is a fun kit for sure! :)

[@DeeegerD]

I will probably run it at only 1.5 to 2 amps as I think that is the limit of my transformer so likely the case will do as a heat sink. How do you find the pots for adjusting, would 10 turn be worth while (I suspect so).

[@voltlog]

Digger D 10 turn for the win! If you're considering using this as a lab power supply you will appreciate the finer adjustment into the mV range or mA range.

[@DeeegerD]

I thought so -thanks.

[@dinah-leemiller8933]

Hi, I build the circuit, but when I switched it on R2 gets really hot and after a while U2 also gets hot and needless to say it does not work. Any suggestions?

[@voltlog]

First check that each component is correctly mounted on the PCB, next make sure you use AC input.

[@dinah-leemiller8933]

Thanks, think my issue was finger trouble. I got it to work, but R2 still gets pretty warm. If that's normal I just leave it as is and start building it into a box. Thank you for the advise

[@voltlog]

R2 should not be warm, I can't check right now but I don't remember that resistor getting hot on my build.

[@Elecifun]

Hi, did you get around to doing ripple measurements under load conditions?

[@voltlog]

I have just finished assembling this kit into a complete unit with enclosure. I did a couple of measurements and I need to make some improvements. I will do the improvements and the measurements in a future video.

[@Elecifun]

VoltLog I am at that stage right now just putting it all in enclosure. Not a lot of capacitance for a 3 amp load.

[@Elecifun]

VoltLog So do I wait for the video for feedback?

[@voltlog]

I'm waiting for some parts to be delivered before I can start preparing the video, it might take a while.

[@crocellian2972]

Good job. I know you build this out properly in another video. But that 24 V linear should be built. Tons of control gear runs at 24 V and it would be very useful to pull it out to a dedicated banana plug for breadboard work on control PLCs, etc.

[@Arek_R.]

In my kit that biggest cap was from nichicin, I was really surprised.

[@voltlog]

I would be surprised too if my cap would be from "nichicin" :-)

[@Arek_R.]

nichicon I meant xd

[@adamsucksatyt]

Mine is made by Chongx :/

[@Ivo--]

Apart from the negative voltage issue the 7824 has a 2V dropout so you would need _at least_ 26 VDC on the input, 24 VAC rectified and smoothed can be almost 34 volts so the 24VDC was way too low.

[@voltlog]

true, but the 7824 is not critical, it is there just to offer a 24V rail for a fan or to power something else external.

[@adamsucksatyt]

@@voltlog to make it look neater and more professional by having the cooling fan connected to the unit... And not to a separate unit

[@adamsucksatyt]

I'll be replacing the 7824 with a 7812 cuz I don't have 24V fans, and the case I've prepared has a 12V fan built in so 7812 is mandatory

[@AxellTh]

I only have a 2.5A transformer. Will that do or does it have to be 3A?

[@TheMegaloloful]

3A is the max. current so anything below should work, yes

[@adamsucksatyt]

@@TheMegaloloful But it'll be weaker at higher voltages. I used a 24V 2A transformer, since it was the only one I had laying around, and I calculated that under 16V I can get 3A And I need 3A in the most common voltage range (1-13 V) So I'm OK with that.

[@kennmossman8701]

@@adamsucksatyt Pulling 3A from a 2A transformer is NOT recommended. It can over-heat/ Use parts withIN their rating

[@timbilliet1050]

i'm having trouble finding a good transformer for this kit,

[@englishrupe01]

Theres a ton of them on ebay. 24v with anything up to 90VA? Loads of em, and anyway around 50va is fine and will stop you blowing it up with too much current. Dont pay more than $20. Here's one i just got and they have plenty: www.ebay.com/itm/Sloan-EL154-120-24VAC-Transformer-Free-Shipping/333196249799?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

[@bloguetronica]

Nice video! However, I find it hard to believe that this supply will be capable of delivering the full 3A, especially when delivering low voltages. The dissipation across that pass transistor will be too much for the heatsink to handle, even if the transistor can handle it. The power supply seems to be using a single 2N3055 as per the schematic, and it is mounted on a separate heatsink. The transformer has a fixed tap, and probably will get out of its SOA in the above conditions. My bench supply uses a scheme like that, but to minimize dissipation, it uses a transformer that has several taps. So, if a low voltage is needed, the PSU uses the lowest voltage tap from the transformer to minimize the voltage drop and the dissipation across the pass transistors. It uses three pass transistors in parallel mounted on a big heatsink, three 2N3055s for 5A.

[@voltlog]

Sure it won't be capable to dissipate the heat generated from a low voltage high current output setting but that's not a common situation. It would probably be ok for a a couple of minutes and if you really need that kind of setup often you probably need a more specialized bit of gear. For the average hobbyist this will do fine.

[@bloguetronica]

Well, IMHO, this supply is overrated. It should be limited to just 1A and the voltage of the transformer should be halved. It would still be a useful supply, but this would ensure that it always operated safely and well within specs. For instance, I designed a 200mA precision supply where the pass element is a MJD31C (the SMD version of the TIP31C). Mind that this transistor is rated for 3A. This may seem overkill, but you have to take SOA into account. SOA considerations apart, this supply seems to be well designed and will do the job. It doesn't have to be a super top-of-the-line supply, I agree on that. Unlike Dave Jones, I don't roast a product just because it is affordable instead of lab grade.

[@iceberg789]

that linear current limiter must be getting very hot every now or then.... any over heat protection would have been nice.

[@abhishekbhattacharya1618]

Voltage not adjust how can slov it????

[@nilsz7354]

I put 28v ac but it doesnt turn on. Have i burnt somethig or i can put 28v ac?

[@voltlog]

input is 24V AC

[@nilsz7354]

VoltLog So I burnt something in the circuit?

[@voltlog]

It's possible, but I don't know.

[@adamsucksatyt]

Miraculously, mine handles 30V AC fine....

[@mihaiharbuzariu6742]

hello, did you try the short circuit protection?

[@voltlog]

Mihai Harbuzariu not really short circuit protection but it has CC mode which will limit current based on your setting. I haven't had issues with this power supply and I've short circuited the output many times.

[@mihaiharbuzariu6742]

VoltLog hello again , i did put everithing together , and i'm geting only 11v at output and the led stay on from the moment i plug in the socket, what does mean this? i have a short on the pcb? because from what i see is nothing wrong...any advice i will really appreciate

[@voltlog]

Mihai Harbuzariu Hi, I would suggest checking that every single component is correctly oriented and correctly soldered.

[@michaelo2l]

+VoltLog Check D8 is actually a zener and in the correct way around... check Q3 polarity...

[@johnchung6900]

Where did you buy the kit from? I can't find it.

[@voltlog]

I have added the link the description of the video.

[@johnchung6900]

VoltLog Thanks. How does the performance compare to the Gopher? Any better or far lacking?

[@voltlog]

John Chung Haven't done any measurements so far. At least in terms of noise it should be better considering it is a linear supply.

[@johnchung6900]

VoltLog Okay will do the order. Takes for the info.

[@voltlog]

no problem!

[@nicklaspersson4687]

I got the same kitt...it think. I'm halfway thru building it. Problem is i can't for the life of me figure out where to put the 2 pcs of 25pF ceramic capacitors(4mm in diameter). On other bright side the 330uF/50V capacitor was a nichicon(witch is good brand "IF" it is). Anyone else got leftover components with this kit? If this thing works out ill mount it with 10 turn pots and some cheapo digital voltage / ampmeter. Looking for recomendations on this.

[@fred9za]

thanks for this vid bought my own board and will be using it for low current situations looking forward to building it

[@milanmladenovic]

Hello, I had same "problem" with this board and now it is "fixed". Thanks

[@peckelhaze6934]

Good video and good explanation as to what was wrong.

[@DanielsAsoZa]

I bought this kit with the intension to use a switching power supply instead a linear transformer because one of this is very expensive and it's also very heavy and big and i don't like it. So i get a 24 volt power supply i connected at the terminals of the bridge rectifier and i also put -5 volt at the opamp but nothing is working. The opamp gets hot and at the output i get around 0.4 volt like in the video. Somebody can help me? sorry for my terrible english

[@voltlog]

+Daniels this power supply kit only works with AC at its input.

[@mbaker335]

The pass transistor here I believe is a TIP3055 or equivalent. This is a 90 watt device at 25c, less at higher temperatures 30v at 3A is 90W. Woaaaa!!!!!!!!!!!!. Before even thinking about this circuit buy as a minimum three TIP3055s and three load sharing resistors at say 3 watts. For a 90watt supply I would want at least 270watt pass transistor capability. In my case I am also using a 6amp toroid 24v transformer. Personally I would only ever draw a maximum of 50% of the full rated current from a good quality transformer. It all depends if you want to rely on what you build.

[@Arek_R.]

You are crazy overkiller. There is no need for second and even third transistor, just good cooling at it will be ok. Also 100W good quality transformer will be ok, we dont need 50% margin.

[@mbaker335]

At uni we were taught to aim for 10x over specification if possible. A 100ma circuit use 1amp parts. It is all about reliability, longevity and catering for the variation in component quality. I finished this supply and used two transistors. However I paralled the secondaries to give 12v at up to 12amp. The worst case 3amp temp of the large 2.2c per watt heatsink is 96c. ( 191c for a 30v supply). The transformer is stone cold as is the internal circuit. Good safety margins means I have screwed the case shut and never expect to have to open it for repair.

[@Arek_R.]

I also use 1A diode with current at 100ma, because package and price is same. But 10x more that needed in many cases is ultra overkill, I never heard something like that. With two transistors and 12VAC/24VAC tap switching we could run at 8A... Or if we are going to build 3A linear psu its good to use 4700uF main cap, or two 3300. But 30mF cap(10x than minimum) is absolute overkill for 3A psu -,- I know what im talking about, I have expirience, I work in high-end goverment/military grade access electronics production.

[@bassblaster505]

if you add a fan why not just replace the 24V regulator with a 9V or 12V one? all fixed voltage regulators have the same pinout.

[@voltlog]

you could do that, but you need to install it on a heatsink, depending on the power draw of the fan that regulator will get hot.

[@pieceofpotato7883]

can I just skip the ac to dc coneverter and just simply use a 24v dc supply?

[@voltlog]

Nope, this kit will only work with AC input.

[@pieceofpotato7883]

+VoltLog but there's one video showing that he skipped all tha rectifier and filtering cap and just use it with dc supply

[@pieceofpotato7883]

+VoltLog but if I cant, can u teach me how to rewind a 36v transformer to 24v. bcs I only have that now

[@pieceofpotato7883]

+Muhd Faaris or can I just use 2 12v transformers?

[@voltlog]

sure you can use two 12V transformers, or two taps from the same transformer.

it not working because input is AC not DC voltage.

[@Gower5555]

exactly, it was the first thing that crossed my head to. The funny thing is that if you just take a look at the circuit , you can see that it has a graetz bridge on it, wich means that it requires AC.

[@RobinCernyMitSuffix]

It does not require AC for the "load" part of the circuit, but the opamps are needing a true zero volts.

[@ShahZahid]

He connected the wires to the output to the rectifier it needs negative voltage with positive voltage

[@primof80]

hi voltlog is there a chance to u could provide some tutorial how to upgrade this kit up to 5A current power input please

[@voltlog]

Sorry, I have no intention of upgrading my power supply to 5A but here is a forum where allot has been discussed about this power supply: electronics-lab.com/community/index.php?/topic/26825-0-30-vdc-stabilized-power-supply/

[@atheera349]

can i use ups transformer to power this psu ?

[@voltlog]

not sure what output windings you have there..

[@atheera349]

how can i calculate the output AC current of my transformer then?there is no info on the transformer

[@MBraveny]

Už jsem koupil druhou Kit z eBay první jsem svou neopatrností zničil zkratem na výstupu.I po výměně součástek se mi to nepodařilo rozběhnout tak jsem si objednal druhou Kit osadil jsem vše jak má být a nefunguje nevím proč nezjistil jsem

[@CezarySiw]

it would work with a DC PS. You just need to make sure you hook it up before the bridge, making sure the minus goes to AC2

[@ProdigalPorcupine]

+Cezary Siwek - It won't work from a single DC supply, it needs AC or the charge pump circuit that generates the -5V rail will not work. To use DC you'd need to also supply the -5V rail, ie a split rail supply. The designers made it like that to keep things simple for the kit builder.

[@hasany.748]

ProdigalPorcupine designer did not design this kit like that way, they have just copied famous linear cc cv power supply schematic and made a kit out of it. And yes you are right , one need to supply negative voltage tot the circuit while operate it with a dc supply. But split rail supply is hard way to go but icl7660 is neat charge pump with its several cents price tag:)

[@dimi-eu]

Man, thanks ! I can not talk about your video as quality, but I sure can tell You that you have good idea/s for Content ! I like the idea of troubleshooting an assembled Power Supply that has capabilities for both - Voltage Regulation & Current Regulation. Thanks again, and keep that spirit :-) btw: I added the video to my "watch later" and when I have more time will watch it and possible do the schematic or use some ideas from it for my power supply, cause I bought one for 150EUR (from ~German Manufacturer, but it is "made in China") and the problem is 30V@5A tops, but not very flexible :| So I take the decision instead of buying a new one, which will be my 2nd lab power supply I will build one myself as I though even the 1st time. bb

[@voltlog]

Thanks! I definitely recommend building this power supply.

[@tectalabyss]

Hello. Mr Steve Wagner recommended your channel. In one of his videos. I subscribed, Liked Shared and added to one of my playlist's. .

[@voltlog]

Hi, thank you for watching!

[@pieceofpotato7883]

+Alex Tomin here's where I get it from

[@robh1908]

I'm a bit surprised here and I think you were testing your viewers. You know very well when you built this that you had put together a full bridge rectifier. So what's the deal?

[@voltlog]

no testing going on, it's just how this power supply works, it needs AC to derive a negative rail.

[@robh1908]

Ok sorry, I thought you had a basic understanding of electronics.

[@robh1908]

All he had to do was bypass the full bridge rectifier and it would have worked with the dc ps.

[@voltlog]

Probably the lack of knowledge makes you think that but if you would take a look at the schematic you would understand what I am talking about. Also read the other comments, you are not the first one to be wrong..

[@Unordung]

Did you watch the video? For example at 14:46 you can see the output goes directly to the DMM and the power supply is connected to the leads of the rectifier directly via alligator clips! Yet here you are quite rudely suggesting that a quality content maker on youtube is incompetent! The fact is it was explained in the video why it did not work in this configuration so your attitude is beyond perplexing. How about rather than being ignorantly arrogant you take some time to learn electronics before you try to be a critic. ;)