I have a ten year old Rheem Heat Pump with installed auxiliary heat kit. I recently installed a setback thermostat, and when I finished I tested the AC first. It started after a few minutes delay as normal for the thermostat. It worked fine, cooled down well. I let it run a few minutes, then turned it off. Waited a few minutes. Then switched to heat. Again a few minutes delay before the unit came on. It came on, I raised the thermostat setting several degrees above ambient as per installation instructions for the thermostat. It was working fine, but suddenly, before I could check air temp output at registers, the Heat Pump shut down, no blower, nothing. I checked the indoor, and outdoor breakers. I opened the electrical access panel on the heat pump, and checked the six large fuses, none were blown, all had proper voltage at both ends. Heat Pump is unresponsive to anything. I called the maker of the thermostat, Filtrete 3M, and spoke with a technician. We walked through all the troubleshooting to doubly make sure all wires were properly connected. I noted that I was getting NO voltage readings on any of the thermostat wired. The thermostat was operating on battery power. It has a 24vac power line from the Heat Pump as its primary power, but there was 0 voltage at that line as well. The only conclusion we could come up with was a blown transformer in the Heat Pump. So, I checked the only transformer,a 208/240vac 50/60hz primary, 24/40vac secondary. There was 240vac across the primary terminals, there was 0vac across the secondary terminals. The 24vac pretty much feeds power to all the relays, the contactor, and the blower fan control circuit board. I manually activated an exposed, spring-loaded double contact terminal on the contactor. The comressor/compressor fan both came on , and operated as long as I held the contacts closed. As soon as I released the contacts, the compressor/compressor fan stopped. I checked all the points that should be showing 24vac. All showed 0vac. Am I correct in my assumption of a blown transformer in this case?