20-09-2019, 06:04 AM
Looking at the PY81 data sheet: http://www.r-type.org/pdfs/py81.pdf it looks like it can run up to 150mA continuously. In normal service it would be running at higher peak currents. Difficult to say what maximum reservoir cap. Datasheet says 4uF boost cap but that has little relevance to a 50Hz rectifier. They are cheap and tough so no need to worry about damaging one.
You'll need to supply 17V 300mA for the heater. HK insulation is excellent so the heater winding insulation isn't critical. Warm up is slow due to the heavy HK insulation.
If you have a Megger you can test the transformer up to the voltage it works at. Don't forget that the peak voltage is RMS voltage x SQRT(2). For a 250V winding you're unlikely to have any trouble. If you're using a 350-0-350 transformer and a half wave rectifier from the 700V total then the insulation needs to be good to over 1000V.
For hlaf wave recitification you need to substantially derate the transformer. Not much more than half the current you could run with a bridge.
You'll need to supply 17V 300mA for the heater. HK insulation is excellent so the heater winding insulation isn't critical. Warm up is slow due to the heavy HK insulation.
If you have a Megger you can test the transformer up to the voltage it works at. Don't forget that the peak voltage is RMS voltage x SQRT(2). For a 250V winding you're unlikely to have any trouble. If you're using a 350-0-350 transformer and a half wave rectifier from the 700V total then the insulation needs to be good to over 1000V.
For hlaf wave recitification you need to substantially derate the transformer. Not much more than half the current you could run with a bridge.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
