Thanks for your reply. According to my measurements at the LM2940 - when switched on cold - it measures 8.9V at the input and 4.5V at the output. When normal operating (same as switched on hot) it's 12.5V at the input and 4.75V at the output. It seems that something squeeze high power at the low voltage level when the machine is cold and after some time it gets back to normal. I've measured the capacitors, they seems to be good but I will double check. According to your diagram are the D1 and D13 zener diodes 5.6V and 4.7V respectively?