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04-09-2021, 07:41 PM
Hi John
No loads and high mains AC.
It looks like the LV PT "out" is one winding, reflecting the lack of loading. The PTs have dual secondaries, both of which must be used. In the case of HV this is taken care of; for LV you decide their orientation (series / parallel) for the heater voltage desired. In this case series for 12Vdc heaters.
The PTs have poor regulation because they are small and open voltage can be 20% for 12VA and 30% for 6VA units measured with 115Vac input. Add the percentage difference of your high mains.
Raw Low-V will be the full DC produced by the bridge output and is easily 16v to 18V. For W3 to be so high you might have any of D3,4,5,6 reversed. If those are as they should be, try a load of one tube heater.
No loads and high mains AC.
It looks like the LV PT "out" is one winding, reflecting the lack of loading. The PTs have dual secondaries, both of which must be used. In the case of HV this is taken care of; for LV you decide their orientation (series / parallel) for the heater voltage desired. In this case series for 12Vdc heaters.
The PTs have poor regulation because they are small and open voltage can be 20% for 12VA and 30% for 6VA units measured with 115Vac input. Add the percentage difference of your high mains.
Raw Low-V will be the full DC produced by the bridge output and is easily 16v to 18V. For W3 to be so high you might have any of D3,4,5,6 reversed. If those are as they should be, try a load of one tube heater.
