The yellow light is on means that you at least have the standby 5vdc power supply section is working, look at the rest of the output of the power supply, you should have 12vdc, and 24vdc. It can be that the main controller is not sending the turn on signal to the power supply to turn on the 12v and 24v power supply sections. Start checking. You can get parts here: http://www.shopjimmy.com/catalogsearch/result/?q=Protron+PLTV-37+ Please post back what you find.
Answers & Comments
The yellow light is on means that you at least have the standby 5vdc power supply section is working, look at the rest of the output of the power supply, you should have 12vdc, and 24vdc. It can be that the main controller is not sending the turn on signal to the power supply to turn on the 12v and 24v power supply sections. Start checking. You can get parts here: http://www.shopjimmy.com/catalogsearch/result/?q=Protron+PLTV-37+
Please post back what you find.