Does anyone know the primary and secondary winding resistance for a Hammond 370BX (with a 230V primary)? I am trying to work out what would be needed to meet the minimum resistance for a valve rectifier (EZ80, and yes I know it has a 5V winding but I will be using additional filament transformers). I can't spot anything obvious in the datasheets.
The pdf datasheet has all the resistance values and off load voltages required for psud
370BX - Hammond Mfg.
https://www.hammfg.com/files/parts/pdf/370BX.pdf
370BX - Hammond Mfg.
https://www.hammfg.com/files/parts/pdf/370BX.pdf
The DCR is in the datasheet https://www.hammfg.com/files/parts/pdf/370BX.pdf
EDIT: sjs beat me to it.
EDIT: sjs beat me to it.
Marvellous, thanks. So from my reading of that and the EZ80 datasheet the secondary resistance of 435ohm should be sufficient for 550V CT supply without extra resistors?
One neat trick to protect the output transformer is to put a UF4007 in series with the tube anodes.
If the tube shorts or arcs internally there is less chance of damage
If the tube shorts or arcs internally there is less chance of damage
You should calculate the effective transformer winding resistance as 271 ohm for a 230V primary. The 435 ohm is for the total secondary. 271 ohm is greater than the required 175 ohm from the EZ80 datasheet for 50uF.
PSUD2 can be used to calculate the initial peak current, and continuous peak current for the datasheet conditions, and then you could use those peak current limits to redesign your power supply and confirm EZ80 operation would still be ok (eg. if you wanted to use 100uF rather than the datasheet 50uF).
PSUD2 can be used to calculate the initial peak current, and continuous peak current for the datasheet conditions, and then you could use those peak current limits to redesign your power supply and confirm EZ80 operation would still be ok (eg. if you wanted to use 100uF rather than the datasheet 50uF).