On Tuesday, July 28, 2020 at 7:44:42 AM UTC-4, Jeff Urban wrote:
If the cathode is positive I can see why to put DC slightly higher on the filament. It will prevent any conduction I would think. However +70 is up there. What cathodes are at that high a positive voltage ? All you need is an equal or slightly higher positive voltage.

I guess maybe for a common plate stage. (cathode follower) Perhaps a triode single phase splitter to drive push pull output tubes.

As far as getting rid of hum, you have to rectify that 70 volts, so why not just rectify the damn filament voltage in the first place ?

You never know what kind of drugs these engineers are on.

I remember an RCA TV like a CTC211 or something, projection. They had a string of like seven transistors just to turn on the convergence subsystem. Why ? And it wasn't like there were a bunch of protection lines going to it, just a voltage and that's it. It was also not in the feedback loop.

I think they just want **** to be as hard to fix as possible.



I think it's time to go back to A batteries..