Will this work as a heater for 300b?

[tomchr]

...or use a switcher running off the 12 V winding. That's what I use.

~Tom

 

[Wavebourn]

Yep. You can't generate 5 V from a 6 V AC transformer winding using a linear regulator.

I can. 6.3V+6.3V, pair of Shottky diodes, 15,000 microfarad cap, and MOSFET, getting 6.3V regulated and well filtered.

Here is 12.6V version attached, for 6.3V I use 5.6V Zener.