Anyone familiar with #Canon #pixma power supply #ElectronicsRepair ? The #k30351 #adb0250620G labeled power supply should output 24 and 36 V, but it outputs 10,8 and 8V. The power supply IC NCP1236 is switching but only once every 3 milliseconds for one short pulse. Supply voltage for the SMPS IC is stable in the "happy" region acc. to the datasheet (~15V).
I already replaced the supply cap for the IC as the ESR was "high" (~5 Ohms). This was plugged in 24/7 for 10 years so that capacitor served a fair amount of current pulses.
I'll try to load the output to check if the feedback loop is actually closed and if it just regulates for the wrong output. Maybe the TL431 is unhappy. Another thing I'll try is to back-feed the output while off and check if there is output on the primary side of the optocoupler. Those tests should indicate if the SMPS IC is unhappy for some reason.
Diodes, fuses, transistors are ok and actually this is a relatively simple SMPS, no PFC, no fancy filters...