12v 30a Power Supply Repair

Back during the summer of 2016 KB4RMA had one of the cheap 120v-12v 30 amp power supplies go “pop” on him due to extreme heat. I finally got around to looking at it and found the thermistor had pretty much exploded. Using a schematic for a very similar power supply and comparing it to another working unit we found that the part in question was an NTC 5D-15 Thermistor (data sheet). I replaced this component and the power supply is functioning properly again. After testing with no load I powered a 65w Kenwood TM-281 VHF radio during an ARES and SKYWARN Training Net and connected a 26Ah SLA battery to charge. The power supply had no voltage drop and the internal fan cycled on and off as expected. These are great power supplies and don’t cause and RF interference that I’ve been able to detect.