The only substitution listed for 35W4 is HY90 and that's a foreign number.
If you don't need a lamp you could replace the tube with a silicon diode and resistors. Use a 1N4004 or better diode. Connect the anode end to pin #5 of the 35W4 socket. The cathode to pin #7. A small value resistor, 22 to 47 @ 1 watt is series with the diode will help keep the voltage closer to the level given by the 35W4.
Add a power resistor about 250 ohms @ 10 watts between pins #3 and #4 of the 35W4. This will replace the filament in the series circuit. You may also need to jump pins #4 and #6, depending on the circuit in your radio.
Norm
: Can anyone tell me if there is a replacement tube for a 35W4 Rectifieer Tube. Thanks!!!!