I said something wrong at about 6 - 7 mind. I said itvregulated voltage fine, but meant ti say it regulated voltage FINE ACCORDING TO ITS DISPLAY BUT NOT IN REALITY. I had in mind the hack I'm currently doing for which that 200mv error does not matter.
Regarding my comments about "tag soldering" directly to the tracks, I wanted to clarify that my problem is really that when desigining the board you should and can arrange appropriate mounting holes, then you use them! in this case they have the holes and completley ignored them, in order to save a few seconds. When you need to do a mod or something often there is little choice, but look at mod wires from good manufacturers and you will see them tacked down or attached to a wiring loom . The real problem however is when "tag soldering" if you leave long fairly heavy wires free to flap around in the breeze, that is a recipe for them breaking either the solder breaking, the track pulling off or the corner where the wire joins the solder breaking. Soldering to the flat of a connector is less bad (it allows easy maintenance, but just take the time to hook it through the hole (dont tie it up like a knot) and ensure again that the length of wire is not flapping about - but ideally if it is degigned for crimp connectors then use them!
quick question, i have this power supply but when i turn it on and turn the current knob the green light does not come on so i can't adjust anything, i can't figure out how to get it working, can you give me an idea what can cause that?
Well there are quite a lot of things - First to how it should work. Without load connected (just connect a multimeter) and current turned even a tiny bit clockwise the green LED should light and voltage be present on the output and displayed on the top meter assuming you have turned the voltage pot a little bit clockwise. I mention in the video at about 5:30 about the problem setting current limit (which you can't really do), but I'm guessing your problem is not just setting the limit but that the green light never comes on. So without more detail there seem to be a few possibilities - 1. There is a short circuit on the output, this will mean it will always current limit and the red light will be on and voltage meter will be 0 or very close to 0. 2. The most helpful is if it is just a display error and actually it works, just the LED does not - turn current fully clockwise. If the voltage display now displays a voltage that changes with the voltage knob then there should be a voltage present on the output and it is likely working - connect it to something to power and it should start reading current, you can then turn the current limit until the voltage starts to drop and you have found the current limit position for that particualr current. 2. If the red light is on permanently even when you have nothing connected to the output and voltage shows 0 and there is no (or little) voltage on output- then the first question is if the current pot plugged in properly to the main board? 3. If symptoms are as in (2) and the Pot is plugged in correctly then it is likely a problem with the current limit, one end of the pot should connect to a fixed reference voltage, the wiper connects (perhaps via resistors) to an operational amplifier and the other side of the op anp goes to a current sense resistor - or possibly another op amp then the current sensor, that I think I show in the video. So the fault can lie anywhere along that chain of components. 4. Fianlly the actual switching regulator might not be operating (which is a more significant problem) and so is not even generating the voltage for the output. I seem to recall there is a separate circuit that generates power for volt/amp meter display etc so. Obviously if it is new, then you should just report it as not working and get it changed or refunded including postage (Paypal and credit card companies can also do the refund if it proves troublesome). Of course you might not feel it is worth the hassle etc and decide to repair it, in which case I hope the suggestions above help, but remember these are just pointers where I would start looking - I can't diagnose a fault remotely.
@@MakeOrRepair first off thanks for the reply, 4. i think that point might be the problem, what i discovered is that if i switch it off and i turn the voltage knob and the current knob then i turn it back on it shows voltage and current and then it immediately drops to 0, at first i was just testing in diode mode to look for a short but i wasn't finding any short so i plugged it in and i start testing voltages and i discovered that 12 volts wasn't present, my conclusion is the mosfet has an issue, i maybe wrong, i removed the two mosphet with the phins and tested them, when i charge the gate it opens and closes immediately, from my understanding it suppose to stay open and it should only close if i short it, i am new to board repair so i am just feeling my way through the process, i am basically trying to teach myself to do board repair :D
@@unlockaccount212 YOu can learn al lot about design and electronics just by fault finding - I wish you well, of couerse it is both easier to fix and easier to learn if you have the service manual!!. I suppose I should do a warning first - please take care near the capacitors and preferably dischare them through a resistor (something like a recalimed 2.2K 10W is ideal for switched mode supply capacitors, some people use old incandecent light bulbs) or just check voltage has dropped below about 30V with a multimeter set on highest volt range - even the metal cans on the switch mode section can hold hundreds of volts. BTW if you use a wrist strap it must have at least 1M resistor in it - you don't want one hand grounded and the other at 300V! Anyway warning given! My mantra for repairs, 1. visual check 2. check the voltages are present and correct, after that if a switch mode power supply (whatever type) is not working then the power MOSFETs or the transistors that switch any coil to ground are very high on my list of quick checks, somethimes there are smaller bipolar transistors that drive the MOSFETS/Power transistors and they seem to fail frequently too - once I've discounted those then it is time to engage brain! Regarding your comment on MOSFETs opening and closing, the easiest is just to use a simple low cost tester from ebay to test it. But regarding the operation it should stay on as long as you keep the drive voltage on the gate (assuming the voltage is high enough). So assuming it is n-channel then to test you can connect a power supply - the source to 0V, and the gate to a voltage whatever the datasheet states is Vgs (on) or a bit higher. You can then connect an LED and suitable resistor from + to drain and it should stay on as long as the gate is connected to +, then turn off if you connect the gate to 0V. P-channel is the opposite, connect source to +, drain goes through the resistor and LED to ground, then when the gate is connected to ground the LED should light and stay on, if you connect the gate to + then it should turn off. Hope that helps a bit, not easy to describe in text. Pete
@@MakeOrRepair well said brother, thanks for the help, i'll try and see what i can do, i know you could of helped better in real time rather than text, thanks a lot thou, if i don't get any justice i'll just have to buy another thanks
I said something wrong at about 6 - 7 mind. I said itvregulated voltage fine, but meant ti say it regulated voltage FINE ACCORDING TO ITS DISPLAY BUT NOT IN REALITY. I had in mind the hack I'm currently doing for which that 200mv error does not matter.
Regarding my comments about "tag soldering" directly to the tracks, I wanted to clarify that my problem is really that when desigining the board you should and can arrange appropriate mounting holes, then you use them! in this case they have the holes and completley ignored them, in order to save a few seconds. When you need to do a mod or something often there is little choice, but look at mod wires from good manufacturers and you will see them tacked down or attached to a wiring loom . The real problem however is when "tag soldering" if you leave long fairly heavy wires free to flap around in the breeze, that is a recipe for them breaking either the solder breaking, the track pulling off or the corner where the wire joins the solder breaking. Soldering to the flat of a connector is less bad (it allows easy maintenance, but just take the time to hook it through the hole (dont tie it up like a knot) and ensure again that the length of wire is not flapping about - but ideally if it is degigned for crimp connectors then use them!
i had the same problem but i did just reflow the ht837dk and it works again
Handy, and if I recall that is just a 4 part op amp, so v. Low cost if it needed replacing. Hopefully the rest of the original soldering is better.
quick question, i have this power supply but when i turn it on and turn the current knob the green light does not come on so i can't adjust anything, i can't figure out how to get it working, can you give me an idea what can cause that?
Well there are quite a lot of things - First to how it should work. Without load connected (just connect a multimeter) and current turned even a tiny bit clockwise the green LED should light and voltage be present on the output and displayed on the top meter assuming you have turned the voltage pot a little bit clockwise. I mention in the video at about 5:30 about the problem setting current limit (which you can't really do), but I'm guessing your problem is not just setting the limit but that the green light never comes on. So without more detail there seem to be a few possibilities -
1. There is a short circuit on the output, this will mean it will always current limit and the red light will be on and voltage meter will be 0 or very close to 0.
2. The most helpful is if it is just a display error and actually it works, just the LED does not - turn current fully clockwise. If the voltage display now displays a voltage that changes with the voltage knob then there should be a voltage present on the output and it is likely working - connect it to something to power and it should start reading current, you can then turn the current limit until the voltage starts to drop and you have found the current limit position for that particualr current.
2. If the red light is on permanently even when you have nothing connected to the output and voltage shows 0 and there is no (or little) voltage on output- then the first question is if the current pot plugged in properly to the main board?
3. If symptoms are as in (2) and the Pot is plugged in correctly then it is likely a problem with the current limit, one end of the pot should connect to a fixed reference voltage, the wiper connects (perhaps via resistors) to an operational amplifier and the other side of the op anp goes to a current sense resistor - or possibly another op amp then the current sensor, that I think I show in the video. So the fault can lie anywhere along that chain of components.
4. Fianlly the actual switching regulator might not be operating (which is a more significant problem) and so is not even generating the voltage for the output. I seem to recall there is a separate circuit that generates power for volt/amp meter display etc so.
Obviously if it is new, then you should just report it as not working and get it changed or refunded including postage (Paypal and credit card companies can also do the refund if it proves troublesome). Of course you might not feel it is worth the hassle etc and decide to repair it, in which case I hope the suggestions above help, but remember these are just pointers where I would start looking - I can't diagnose a fault remotely.
@@MakeOrRepair first off thanks for the reply, 4. i think that point might be the problem, what i discovered is that if i switch it off and i turn the voltage knob and the current knob then i turn it back on it shows voltage and current and then it immediately drops to 0, at first i was just testing in diode mode to look for a short but i wasn't finding any short so i plugged it in and i start testing voltages and i discovered that 12 volts wasn't present, my conclusion is the mosfet has an issue, i maybe wrong, i removed the two mosphet with the phins and tested them, when i charge the gate it opens and closes immediately, from my understanding it suppose to stay open and it should only close if i short it, i am new to board repair so i am just feeling my way through the process, i am basically trying to teach myself to do board repair :D
@@unlockaccount212 YOu can learn al lot about design and electronics just by fault finding - I wish you well, of couerse it is both easier to fix and easier to learn if you have the service manual!!. I suppose I should do a warning first - please take care near the capacitors and preferably dischare them through a resistor (something like a recalimed 2.2K 10W is ideal for switched mode supply capacitors, some people use old incandecent light bulbs) or just check voltage has dropped below about 30V with a multimeter set on highest volt range - even the metal cans on the switch mode section can hold hundreds of volts. BTW if you use a wrist strap it must have at least 1M resistor in it - you don't want one hand grounded and the other at 300V!
Anyway warning given!
My mantra for repairs, 1. visual check 2. check the voltages are present and correct, after that if a switch mode power supply (whatever type) is not working then the power MOSFETs or the transistors that switch any coil to ground are very high on my list of quick checks, somethimes there are smaller bipolar transistors that drive the MOSFETS/Power transistors and they seem to fail frequently too - once I've discounted those then it is time to engage brain!
Regarding your comment on MOSFETs opening and closing, the easiest is just to use a simple low cost tester from ebay to test it. But regarding the operation it should stay on as long as you keep the drive voltage on the gate (assuming the voltage is high enough). So assuming it is n-channel then to test you can connect a power supply - the source to 0V, and the gate to a voltage whatever the datasheet states is Vgs (on) or a bit higher. You can then connect an LED and suitable resistor from + to drain and it should stay on as long as the gate is connected to +, then turn off if you connect the gate to 0V. P-channel is the opposite, connect source to +, drain goes through the resistor and LED to ground, then when the gate is connected to ground the LED should light and stay on, if you connect the gate to + then it should turn off.
Hope that helps a bit, not easy to describe in text.
Pete
@@MakeOrRepair well said brother, thanks for the help, i'll try and see what i can do, i know you could of helped better in real time rather than text, thanks a lot thou, if i don't get any justice i'll just have to buy another thanks
What's tag soldering? I know what tack soldering is but jot tag soldering.
Just what my old tutor used to call it, it just stuck. I'm not going to correct every slight slip