Pilot tv

[DavGoodlin]

Timmy- Your wattages seem way high, so I pulled out the RCA tube manual. I have a 12" Pilot Tv125 so I'm interested in your application.

A 35W4 can always be eliminated but sometimes the filament is used as a voltage divider in some circuits, mostly for a 6-volt pilot light . See what is connected to pin 6 - the 6 volt heater tap. If 7-cathode is connected to 6, then you have a negative supply appearing at pin 5 that is the rectified, AC potential at pin 6. You will need two resistors to eliminate it in this case. The heater current is 150 mA, so resistor from 4 to 6 is 40 ohms @ 1 watt , 6 to 3 is 180-200 ohms @ 5 watts minimum.

Your results may vary, Can you post a picture of the circuit?

Often a 35W4 is employed to not only drop the AC a bit for a pilot lamp it can provide cheap fusing for the B+ supply because the 120 volts (to B- ground) at pin 4 is reduced at pin 6, and in most AC-DC radios, pin 5 is the plate where the AC connects to, 6 volts reduced from line voltage.

To remove tubes, my motivation is to eliminate possible transformer-destroying failures especially in Zenith radios and HiFi amps like the 6X5 or 7Y4. But sometimes I sub diodes in where the elimination of a tube filament like a 5U4, etc saves about 10 watts on the primary transformer winding. My 1964 Zenith HiFi has 1N4007 rectifiers in for the 330 volt B+ instead of the 5Y3. I dropped the now 360 volt rectifier output voltage back to 330 with a 300 ohm on the rectifier cathodes before the first 47 uF filter cap. The 2x6BQ5 amp draws about 100 mA.