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 PSUAt 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 FirmwareSomewhere 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.