[BrendaAnnD]

I suspect it was a mid-run change and there were a lot of spare 35L6 tubes that they wanted to use up. Since the 50L6 and 35L6 are both 150mA heaters, they can be interchanged if the inline resistance is added/removed. If that resistor is getting to 265 degrees F, it's woefully underrated (and has probably gone up quite a bit in value). Again, if you have a 50L6 handy, I suggest bypassing that resistor and using the 50L6. If not, I would at least replace that resistor with a good wirewound rather than that '20's type dogbone.

An appropriate replacement should be a 100 ohm 5 watt wirewound resistor. This would drop 15 volts at 150mA and should run a lot cooler since actual power would be 2.25W.