Tubes can short or run away. In that case, that cathode resistor will take a beating and could flame up if it is not flame proof or rated to handle that condition.
BTW, I have seen a transmitter for a WW2 fighter plane that used the 1625. Rugged tube also proved to be great for a car amplifier in my youth. Also they were $4.50 a pop around 1990 so that was a win too.
BTW, I have seen a transmitter for a WW2 fighter plane that used the 1625. Rugged tube also proved to be great for a car amplifier in my youth. Also they were $4.50 a pop around 1990 so that was a win too.
Yes, there's also screen current.
If you have over 1W of dissipation but less than 1.6W, a 5W resistor will work fine.
If you use a 1W resistor as a cathode resistor, expect 1-2 years of life out of it.
If you use a 2W resistor as a cathode resistor, expect 2-5 years of life out of it.
If you use a 5W resistor as a cathode resistor, expect to die before the resistor does.
I think mine are from that vintage. Dad had them before I was born and that was 1958.....
Probably the famous AN/ARC 5 transmitter that used a pair of 1625s as RF finals. That should be a hint that grid stoppers are a good idea for this one.
Especially if you're new to tubes, I would strongly suggest against designing a PCB. Tube amps (like any amp) are very sensitive to grounding and layout, and a PCB makes that very hard to change. Furthermore, GOOD LUCK getting any PCB-mount sockets for a 1625. Maybe for the drivers, but I'm not a big fan of PCB-mount tube sockets in general. Maybe with modern PCBs it's okay, but a tube socket sees mechanical stress (changing tubes) and a lot of heat.
I can mount anything to a PCB. If I wanted to I'd take a standard UX7 socket, bend the tabs out and surface mount to pads on the PCB.
But for the 1625, if I use a PCB, I would mount the socket to the chassis and connect it to the PCB with a short wire harness and a board (molex) connector. Tie all the grounds to a star point on the chassis. (I reckon...)