UPS Orvaldi INV12-500W error 20 13 on display. Battery charged, does not start. Beeps 2 times long and 3 times short. Electrolytic capacitors measured, no shorts on transistors or diodes. The original fault was a faulty fuse mounted on the fan heatsink. After replacing it, the unit does not switch on. When the battery is connected, the fan starts at low speed (although I think it should not). When 230V is plugged in, it starts at the correct speed. Maybe someone has had a similar fault and found a solution. A diagram would also be helpful.
