| Electronics > Repair |
| Korad KA3005P power supply faulty/repair |
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| basil:
I am having a strange problem with my KORAD 6005D (60 V 5A model ) !!!! -> Power supply works perfect up to a set voltage of 19V ~ 20V . -> If i increased the set voltage above ( ~21 till 60) & (o/p is enabled ) , i can hear a relay tick sound from the power board at a constant interval . At this time i am getting a voltage discharge ramp at the output terminal . In the front panel display values also i can see this effect ( display works good ) -> i noticed that , If i remove the voltage feedback/sense line from the connector J10 at the front panel pcb the relay ticking stops ( but the power suppy will not work as the sense lines are removed , right ? ) I can share more specific details , If someone can help me to figure out the issue . |
| Kleinstein:
The description somewhat sounds like a problem with transformer tap switching. Maybe a worn out relay contact or a loose wire / blown fuse from the transformer. My guess is that the higher transformer tap for some reason does not deliver power. The 60V 5A version is likely different from the smaller units in some aspects. I would expect a different transformer tap switching at least, to reduce power loss. So a little more information, a few photos of the internals might help. A visual inspection for lose wires, maybe cold solder joints or blown fuses would be the nest step anyway. A helpful point to measure would be the voltage of the large filter cap (e.g. solder temporary wires and measure). It needs some care: the voltage could go to about 80 V and in case of a short there is plenty of power. |
| basil:
You were absolutely right and thank you very much for the inputs !!! It was due to a faulty relay ( K3 in my case ) . Now the unit is working perfect . :) |
| uv3afl:
--- Quote from: mos6502 on January 10, 2017, 07:36:00 am ---Hey, at least something :) Now you only have to program your own firmware and redesign the regulation circuitry. ;D --- End quote --- Yes, KA3005P is really 'at least something'. And no DIY with it! It's not interesting, because it's somewhat classic )) It's a cheapie with more than reasonable functionalyty for it's cost. And here is the PS of my real interest that I build now. Fortunately, it's completely open source and there's no need to develop something from scratch. And I am almost done with it. It works fine but there's still some mechanical work to fit it into the case. By the way it has no cap on output terminals inside by default. It is really fast in regulation and offers LED operations with current limiting. But... there's the other side - on some loads people catch some oscillations. And... Put some output cap on terminals ;) |
| Tony Mach:
So I have a faulty KA3005D… and maybe someone finds the information helpful I have gathered so far (unfortunately I am not done yet). Pinning down the problems with my PSU At my workplace we bought this PSU, and it was broken out of the box. You could press OUTPUT, but it would not output anything… The voltage would stay at 00.00 V and the current at 0.000 A. Otherwise it seemed fine. From time to time one or the other colleague took it, played around with it, couldn't accomplish anything, and then put the PSU angrily back into the shelf… Now I had enough and declared the PSU dead – but I didn't want to give up so easily. Instead of having to put the PSU in the electronics-dumpster I was allowed to take it home. And now it is my problem… With the help of the schematics here I did find out that the power-board (in the rear) is fine. With a voltage on pin 1 I could change the output voltage. The 7-segment displays even displayed the output voltage and current! The problem seems to be localized on the control-board (the MCU, the two discrete DACs with the comparators). With the "calibrate" procedure I could find out that the "zero voltage" is adjustable from about -100 mV ??? to about +200 mV in steps of about 2 mV. The three other calibration settings ("zero current", "max voltage" and "max current") do nothing (sometimes the voltage "blips" when turning the wheel). While I can not rule out a hardware problem, I suspect a software problem. (Maybe wrong values in the I2C-EEPROM?) Going after the Firmware Somewhere I found out that it is a Nuvoton M054 MCU. And oh wonder of wonders, at my workplace we have a Nuvoton Nu-Link-Me. I managed to connect it (see attached image), and I could connect to the MCU right away! In my PSU there is a M054LDN. Success! But no, not so fast, unfortunately the "security lock" for the flash is enabled – so I can not read out the firmware and can not debug it. At least I was able to get a PinView which I attached as a screenshot (whether it is accurate is another question). So I could write my own firmware… Next step: Getting into CooCox with the Nuvoton MCU. Famous last words: How hard can it be to manage a handful of GPIOs? So that is what I have so far. I don't promise that I will be able to follow up on that. Maybe I will, maybe not, or maybe someone else can use that information. |
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