I was just wondering is anyone could see anything wrong with this power supply I’ve put together. When I power it on instead of outputting 170vdc like its suppose to, It bounces around somewhere between 190-260vdc. I am a complete amateur and cannot figure out why it isn’t working properly. Any ideas would be very appreciated. removed link
Need a little more information.I was just wondering is anyone could see anything wrong with this power supply I’ve put together. When I power it on instead of outputting 170vdc like its suppose to, It bounces around somewhere between 190-260vdc. I am a complete amateur and cannot figure out why it isn’t working properly. Any ideas would be very appreciated. removed link
Is there a load or not?
Larry – N7LUF
Oh sorry I didn’t see that the link to my pictures got removed. There is not a load on the supply. I have seen other people online using the same design and theirs stays at a steady voltage where as mine does not.
It’s just a boost converter controlled by a MC34063 IC.
@mitch90 1. Verify thoroughly once again that you have indeed followed the exact schematic connections with your PCB design (if you’ve design that PCB yourself) or verify the soldered connections if it is a point-to-point design. 2. Check if the resistor values are correct and, indeed soldered in the right place since it is extremely easy (if you’re not through) to have resistor values misplaced. ! 3. You must have used the correct value inductors! Since I haven’t seen the schematic I assume there is at least one inductor present on the diagram. You need to have a means of “properly” measuring that inductor. IE: an inductance meter, an LCR meter, or at least one of those cheap “Chinese multicomponent testers” to give you a rough idea if the value is within the “ballpark” specified on the schematic. 4. If there is a VR on the design, try adjusting that. 5. Pay special attention to any electrolytic caps present there (value, placement, etc)
@mitch90 Looking at the pictures in the provided link one can see that R6 needs to have a certain value according to the desired output voltage. On the schematic diagram picture, there is a table (in the bottom right corner) of values R6 can take. So, if you want 180V (out) you need to solder a 6.8K resistor. Now, one thing I’ve noticed: on the PCB picture R6 is pictured as an 8.06K value and this isn’t in that table. So it could be a “typo”. they meant to mark it as 6.8K rather! Now. I don’t know what value resistor you have soldered in place. Keep in mind that some PSU supply designs require a load to be connected before the voltage stabilizes (at the output). I’m not implying this is the case but to verify the theory according to some ohms law calculations you can place a resistor at the output terminal to ground (to mimic your real load (so in case the voltage is indeed higher than desired you won’t damage your (real) load whatever that is: Nixie tubes etc. So, in other words, once you confirmed that R6 has a value (measured value!) of 6.8K give or take 1-5% tolerance and considering that the PSU was designed to deliver a maximum of 5.5Watts of output Power ( approx. 30mA @ 180V) we can calculate the resistor value needed as a “dummy load” knowing that according to the ohms law formula R= V squared over/divided by P . So 180V squared = 32,400 and divide that by the “theoretical power value” of 5.5Watts will result in a resistor value of 5,890 Ohms or 5.89 K.; So considering that this value is not really that critical and it can be approximated a little you can choose the next standard available resistor value. So you can use a 5.6K, 5.9K, or 6.1K or you can even put multiple values in series to obtain the desired value. Keep in mind that, the resistor/s will get a little worm, so be cautious. Another thing to know is to make sure that your supply (input) voltage is within the specified limits (10V-12V) Some ICs are known to lose the driving ability if the supply voltage drops too low and as a result, the output voltage becomes either erratically unstable or way too high! So, once again make sure that the voltage supplied is stable and does not drop (“sag”). Now, please be careful since there are High Voltage levels involved here, and if you are not confident enough and do not know what you are doing I kindly recommend that You Don’t do it at all! otherwise, You’re Doing So at Your Own Risk.
Ok I finally figured it out, The one transistor (2N3906) is marked backwards on the silkscreen. I flipped it and now everything works perfectly. Thanks for all the other ideas and help. I cant believe the amount of time I’ve wasted staring at this lol
@mitch90 TIP: As a future reference, is always a very good idea when you make an inquiry about something that you worked on (or put together for that matter) to post close-up pictures of the PCB on both sides (the actual work that you’ve done). This way, when lots and lots of people view those close-up pictures it is almost certain that someone would have picked that silk problem up very early, saving you all this “head-scratching trouble” and wasted time. More eyes focused on a problem equals way more chances to solve a problem fast. 👍
@mitch90 You can use a “Direct Link” from sites like https://imgur.com/
There are other sites you could save your photo to and provide a link.
Larry – N7LUF