A FEW NOTES: 1. Do NOT try to increase the output voltage above the maximum rating of the output capacitors (probably 16V for a 12V power supply and 10V for a 5V supply) 😜 2. Also as at least two subscribers already mentioned - make sure you CHANGE the voltage markings on the PSU label after you modified it because you quite probably WILL forget that you changed the output voltage after a few months or so. 3. Keep in mind the Wattage - if your load is 12V at 2 Amps that is 12 x 2=24W. If your load uses 14V and it is still drawing 2 Amps that is 28W. Make sure you leave enough enough headroom so as not to overload the PSU 4. Your PSU may have TL431, LM431, KIA431 or some other prefix. They are all equivalent.
My hbp500 generic smps for audio amps is supposed to be 65-0-65 but it's only 38-0-38 I don't think I tested it when it was new but the irs2092 has never had any decent performance at all with it. When I ordered it I selected the 65v option. On the back/bottom of the PCB there is a row of voltage options. Can I modify it to be 65v if they selected the wrong voltage? Edit: also the transformer pins are connected next to each voltage 'option'.
@@Freeknickers24 must be rare that the company includes a transformer with switchable options, due economical reasons (more or less cooper). Its probably that exists different circuit paths for different transformers at installation time. In case that your transformer has such switchable capabilities, you can check the change in the Ohms(resistance) relation (Primary wind Ohms/Secondary wind Ohms) with a decent multimeter for each option (1:1 equal voltage input output, 1:2 doubles voltage and so on)...also, maybe, you need to check the path of protections involved (ie. a rise in voltages, some times, accompanies lowering fuse rates in the same inverse proportion for its amperage, that means 2x voltage, 1/2 fuse amperage and so on...only for fuses but would be other protections involved).
Great video, very informative. About your third point, shouldn't we also consider the current draw? For lower voltages, the current draw might become the limiting factor in terms of safety. Drawing twice the current at half the initial voltage could cause issues, even if the power draw remains the same.
You are an amazing teacher. I really enjoy your explanations and your approach to logical troubleshooting. I truly look forward to the next video and I appreciate you sharing your knowledge with us all. Thank you.
Top Notch Rich, Told ya mate best on youtube. It is a great honor and privilege to pass on your knowledge and experience to the next generations. Very little of us get the chance. Grab it with both hands mate.
I'm wanting to learn how to fix a wide variety of electronic items from radios to computers GPU etc, in future videos would you contemplate fixing and explaining how radios work?. and how to do signal tracing.
Yep great but what happens when someone uses it for something else? You must tell people to change to voltage written on the case. Because what happens is some comes along and breaks my equipment. So now i always change the voltage on the case.😮💨
Yep you are totally correct - it is important to change the label on the PSU - even yourself could forget what you changed the output to in a year or two (or maybe less). I now put your suggestion in a sticky in the comments and highlighted it in the video description. Thank You
That schematic in that pdf is a little incorrect, because I don't know if you have noticed, but the bridge rectifier is connected the wrong way round for a start.
You can put few drops of gasoline in the gap . Wait for few seconds, a little twist and pressure , the glue dissolves and that adaptor can be opened without damaging its casing
since you understand about it, a non related question: can I put white LEDs into the 3,3 V output, just for illuminate de interior of the PC power supply? Just for some modding, asthetic reasons. Or this may affect the motherboard functioning ? thanks!
I have done this on several power supplies, including those dodgy wall warts. But like Richard points out in his comment, pay close attention not to exceed the output capacitor voltage.
Yes but you are limited to the tolerance of the transformer. Transformers are manufactured with the output voltage and current in mind, the number of windings determines the voltage and the wire gauge determines the current. Say for argument's sake you lower the voltage but pull more amps than the transformer was designed for, the transformer could get very toasty and melt its windings and possibly short to the primary side.
@@snipersquad100 Actually Wattage (which is what causes heat) is volts x amps. So decreasing the voltage and increasing the current proportionally keeps the wattage the same. it's much more likely the output rectifier diode(s) would give up long before the transformer winding as they will have a maximum current rating. 😉 Realistically the limits you are going to face are: The maximum voltage rating of the output capacitor(s) The maximum current rating of the rectifier diode(s) The maximum and minimum duty cycle of the PWM controller (which determines the maximum and minimum output voltage) Personally I would use the technique shown in this video for changing the output voltage of a PSU by a few volts only. The one I modified for the Samsung monitor is working fine by the way after several days and my wife is very happy with her new screen
@@LearnElectronicsRepair If you have a 100watt transformer rated for 12v at 8.3 amps, the manufacturer of that transformer would rate the windings suitable to carry 8.3 amp, probably a little more for head room, say 12AWG. If someone hacked the power supply to put out 5v, that transformer could put out 20 amps, this would fry the windings in the transformer.
lol, funny how timed that video is, while i'm also working on a small project for my little brother that requires a change in voltage!! he's been gifted a pc and want to be able to use his gpu in it , but it's a hp compaq(small form factor) that uses a non standard power supply(btx instead of atx) with only 240w output.. he already own a 500w atx , so i'm making him an adapter for the 24 pins connector to the two six pins ones that the mobo needs, the color code for the wires is the same on both side, the only problem is the standby one(purple), it requires 12v instead of the standard 5v for atxs... XD but i won't go into the box, i'll just build a step-up into the adapter to keep it usable in a standard atx built!! Anyway, yet another nice and very useful video of yours saved in my "electronics" playlist!!! Keep it up, i can see a bright future for your channel into the repairs and diy communities, the efforts and enthusiasm you put into explaining everything that you do, and why you do it, as clearly as you manage to do it, makes your videos not only useful, but also fun to watch for those into that kind of stuff!!! :p
Yes - usually by replacing the resistor from REF to Cathode (the 20K resistor) - you can see how to add a variable resistor in the 'Shunt Regulator' diagram on the TL431 calculator datasheet at 14:02
I have tried the same mod on my 24V 6A power supply. I realized that when I changed the output voltage down to 16V and below, it keeps cycling on/off. What could have happened?
That is such a useful instructional video, we all have many old power supplies lying about a be useful to be able to change their voltage , thankyou for posting :)
Simple “fix”! Jst remember that the “total power” should probably be maintained…i.e. if you raise the output dc voltage, the originally rated output current will be LESS in order to maintain the total power spec.
Excellent :) I bet lots of people want to see this same type of vid for computer power supplies. Many people ask how to make one into a variable bench power supply :)
Thank you for your videos. I learn a lot from them. I wonder how to change SMPS Input voltage (from 110V to 240V). I suppose you have to change the input capacitors, with higher voltage and less capacitance. Am I right?
Great stuff, A very handy calculator. I just select my required output voltage in the box, and use the calculate R2 Button.Am not sure what the empty box does, to the left of the three buttons.. Happy Days,
Greetings from Ethiopia, my question is I have some Toshiba laptop charger 19 v not sure but 3-5 amps can I do the trick to use it as my Mobile charger USB c or normal Samsung Galaxy phone? I learned that I can reduce or increase the out put volts by changing the value of the voltage divider resistors to the programmable zener Diod TL431, but what about the amps? Thanks
2:35 - I have had great success getting into these (without bits coming off from the impact of a blunt object) by using a bench vice as a nut cracker: slowly tighten the vice perpendicular to the seam until it breaks a smile. A slight twist of a flat blade and you’re in! There are no breaks in the shell so it can be glued back together as if nothing ever happened! Although, I must admit your method is a mite faster if there’s no need for aesthetics!
Ey up, mentioned this before but not sure if you have come across it, i guess without a board yourself with the issue could be hard to demonstrate - essentially on ASUS motherboards they have fan speed control in the BIOS, when attempting to live plug a fan in - i shorted the pins with a spark, since then the fan will only operate at full speed, all fan control both PWM or DC has gone, there seems to be 3 leg voltage regulators?? near each fan header, is it likely these have gone? i guess they can only be replaced with hot air work station? any info appreciated, cheers
Excellent video, I would love to see a similar mod but instead of a fixed voltage, an adjustable voltage output voltage... I would imagine that you would need to have fixed resistors in place to keep the voltage from going too high or too low.... This would be a great mod for a nice high power supply, possibility from a laptop or even those industrial SMPS that are so cheap and usually have some sort of miner adjustment as it is, for all I know, it might only need a fixed resistance change to gain much more voltage adjustment.... Anyway, thanks again for this great video... I have been looking into these power supplies and how to change their output voltage and this video nailed it....
2:09 - whenever I need to crack a wall wart (walnut?) I use a bench vise to slowly add pressure to the longest side until it splits open far enough to get a screwdriver in to pry it further apart. After repair, I can usually glue the case back together to look factory. Only on rare occasions does this method produce fragments (I.e., when I got in a hurry and applied too much vice pressure too fast,)
What a phenomenally useful and clearly-presented video, thanks!! Off the shelf switching supplies have gone from being dark mysteries to useful, versatile gadgets! Thanks again for one of the most useful YT videos in recent memory!
Although staying below the voltage rating of capacitors is a good practice, that isn’t necessarily sufficient. The output rectifiers not only have a current rating that should not be exceeded, they also have a reverse voltage that should not be exceeded. Conceivably, one could be below the voltage rating of an output capacitor yet have exceeded the reverse voltage rating of the output rectifier. In order to confirm that the reverse voltage rating of the output rectifiers aren’t being exceeded, some equipment is needed that might not be in the possession of the viewer - an oscilloscope is a must, and a variac is also a good idea to have because the “duty cycle” of the wave shape being fed to the output rectifier can vary with the AC input voltage. And the rectifier reverse voltage rating is not going to be printed onto the device like it would be with a capacitor; the specifications for reverse voltage rating will have to be retrieved from the data sheet for the part.
cheers for that. but if we want to change the voltage alot more than what the power supply is designed for, then what should we do? I suppose the transformer winding turns should be changed too? I need to convert a power supply to 2 volt 40 amp . because I can not find this in the market . help me with this please
Yes you can use a potentiometer (variable resistor) in place of the resistor from REF to Cathode. In theory the lowest output would be 2.5V and the highest output would be dependent on the value of the variable resistor, but bear in mind that you may be limited in voltage range by the maximum and minimum duty cycle of the PWM controller.
Thanks for the excellent video. I modified a Sony Playstation 8.8V output SMPS with potentiometer but when I tried to set it at 5V, below 5.5V it goes to cutoff mode( output becomes 0V and after putting off it's input, it comes in on mode again). What is wrong? Please explain.
What happens when you try to mod it? I did mention in the video you can change the output by a few volts but trying to reduce it to less than 50% of the intended output may just mean the PWM controller reaches it's minimum duty cycle and can't go any lower
I very much enjoyed your English accent. I also enjoyed your teaching. It clarified my understanding of the TL 431. And I subscribed to your channel. thanks for sharing.
The way I remember is by using the alphabet, the electrons travel from Anode to the Cathode. A for Anode comes before C Cathode (or K for that matter) in the alphabet. So knowing which direction the electrons flow the Cathode will be the stripe part of the diode and the flat side of a through-hole LED.
@@snipersquad100 The electrons travel from cathode to anode, if they travelled from anode to cathode a cathode ray tube wouldn’t work. You’re thinking of conventional current.
@@stevebabiak6997 I normally qualify that when I speak, the answer mentions electrons travelling from Anode to Cathode. Clearly they don’t. I would phase the answer something like “ using conventional current flow ( + to - ) the diode symbol looks like an arrow showing the direction, using electron flow ( - to + ) the bar in the diode looks like a negative sign”
Use a variable resistor to replace the one between REF and Cathode pins on the TL431. Bear in mind in theory the minimum output is 2.5V but you will also be limited in range by the minimum and maximum duty cycle of the PWM controller. The IC (or mosfet it is driving) may also not like running continuously at high duty cycle. I would use this method for changing the output up or down by a few volts, but you can experiment yourself and let us know how you go on.
Fantastic job going through this application and the programmable zener.....even if your accent to rich, your instruction is vastly richer and so are we. Thank You.
Amazing! Thank you! I certainly did learn something new and will feel more confident if I need to alter any of my PSUs for specific reasons. I have a few spare external hard drive PSUs that could be re-purposed for other things now :D
I'm really liking your straight forward, even simplistic method of troubleshooting. But, it's the challenge of deciphering your accent that brings me back 😉 👍
I recently had to modify a smps and your video was a great resource, thanks very much. Something I learned (that may be helpful to others) is how to remove the enclosure in which the smps resides. Taking care not to burn one’s self or melt the enclosure, place the enclosure in a C-clamp or bench vice and warm it evenly til it’s almost to hot to touch. As it begins to cool, start tightening the screw of the clamp until the pad of the screw and jaw starts to compress the walls. May need to reposition the clamp so you’re in the sweet spot near the corners. By squeezing the warmed plastic you’ll be able to get a lever in between the halves of the housing and with a little torque applied to lever( pry bar or flathead screwdriver) the halves should release. If lucky, the clamping force of the CClamp will pop the enclosure apart without need for any other tools. I found this to a better method for myself as I damaged a few PCBs with the hammer technique. Shockingly,(😂) I didn’t realize I’d damaged the board until I plugged into a mains outlet and heard a loud pop and saw a poof of magic smoke release. Thanks for the video and your expertise.
Thanks, mate! Been watching lots of your videos, all VERY useful indeed. Luv it! One could go to varsity for years and [probably] learn very little really useful stuff like this...
Brilliant - I needed this lecture yesterday to test a Samsung LED screen. Used my variable desk PSU, and found that the screen is broken, with zig-zag lines all over and vertical coloured stripes! If it had not been broken, I would have been doing this today, following your very clear exposition 🙂 Thank you very much!
Great video, your lucky to not have dust in the monitor, or perhaps your environment is very clean. Would be nice if you took a similar PSU for laptop and showed ripple before/after with removed Y caps that connect to ground. I don't have a scope ant myths of increased ripple are making me crazy. I do not need to have neon light bulb light up when touched to USB ports etc, on laptop with typical crappy PSU design.
Excellent, thanks, I've fixed a couple of SMPSes in the past but still hadn't really got my head around the inner workings, it was more by trial and error - your videos have been super helpful, I guess the only question with this hack is if there are multiple rails and voltage outputs - I think one rail is usually controlled using the reference but I haven't gotten my head around how the other rails are controlled - is it purely by way of zeners on the assumption that only one reference rail controls the HV side and the others just play along?
All I have done is use a solar panel power controller from Aliexpresswhich has got variable voltage and current limiting. It is connected to the *12volt rail and can go 1 to 30 volts and with variable current limit its a very cheap and effective power supply
Richard, Wow in just one video their is always a lot to learn from you. Even more to learn and understand when i watch it again and again. Thanks for your time and effort to teach us. Bye for now. 🍻
Great video for learning how to change the output voltage of your smps. But don't forget not to go above the rated working voltage of the output capacitors. If you do then you have to change the change the output capacitors working voltage to match your new output voltage
