Re: Type 45 SETs are NICE!
Posted: October 12th, 2017, 4:47 pm
Roscoe,
Something looks strange regarding your voltages, looks like you have 180V across the tube (Plate to cathode), and 18V (grid to cathode) of bias. At that op point, the current is over 60 mA according to the plate curves, but your cathode resistor size is sized for 35 mA. I would expect a bias voltage closer to 28V, not 18V if the tube was operating in spec.
No matter really, the cathode resistor size is going to keep the current down, and the voltage is low, so you are not pushing the tube at all.
David
Something looks strange regarding your voltages, looks like you have 180V across the tube (Plate to cathode), and 18V (grid to cathode) of bias. At that op point, the current is over 60 mA according to the plate curves, but your cathode resistor size is sized for 35 mA. I would expect a bias voltage closer to 28V, not 18V if the tube was operating in spec.
No matter really, the cathode resistor size is going to keep the current down, and the voltage is low, so you are not pushing the tube at all.
David
Roscoe Primrose wrote:I was using 5AR4/GZ34 rectifiers, which heat up more slowly that the 45. AC heated, direct coupled...
http://n4rp.com/images/5842-45.pdf
Roscoe