steve from Hungary
Hello!
To test, put some load on 3,3V (e.g. 12V car bulb), because the voltage regulator (TL451) works on 3,3V line. If this line is not loaded, the supervisory circuit switch off the supply after short time. To temporary disable this, you can put a short circuit on primary side of the optocoupler (near U2). My unit has TL451 self oscillating. After change, everything works ok!