Charger indicates E20; app may describe it as internal power supply error.

Safety: Internal power supplies are connected to mains; only qualified personnel should service them.

• Observe behavior: If LEDs flicker or the unit repeatedly reboots, suspect the low-voltage supply.
• Inspect visually: With power off, open the charger and look for bulging or leaking capacitors, burnt components, or discoloration near the auxiliary supply section.
• Measure rails: With appropriate caution, measure the low-voltage rails (e.g., 5 V, 12 V) at test points or connectors. Deviations from nominal indicate a failing supply.
• Check for shorts: With power off, measure resistance between low-voltage rails and ground. Very low resistance may indicate a shorted component on the control board.
• Replace board: In most cases, the auxiliary supply is integrated; replace the entire control or power board rather than attempting component-level repair.