I found this circuit in May 1947 Radio Craft. Couldn't 1N4007 diodes be used instead of a tube rectifier?

Rob

Yes.....but: regardless of what rectifier is used, the circuit is NOT safe. Connecting one side of the line to chassis creates a shock hazard---even if the connection only passes one-half of the cycle.

We need to get in our time machine, and get that author re-educated....

EDIT: both cycles of AC go to chassis.....one through a capacitor.

Yes, agree with Mark's assessment.

The circuit would certainly limit fault current since each leg flows through a tube diode.

There would still be plenty of current available let to fry the grounded victim!

Tim

"John" apparently, and erroneously, thought that a 'diode' isolates so that connection though a diode is not "directly to the chassis." All the second diode does is introduce another diode drop, not make the supply 'safe'.

It's a line powered half wave rectifier with an extra, useless, diode to chassis.

And to answer the original question about using 1N4007 diodes instead of the 6H6, it would make the circuit even more dangerous because the solid state diodes would not provide any significant current limiting.

Fixed bias for amplifiers of 120 volts DC? Maybe for some transmitters. I doubt the 6H6 could deliver much current though; one little mistake and the tube is history.

So, the article was not peer reviewed before publication. I'm shocked.

Perhaps the author meant the circuit was safe as long as it was turned off: with the heaters cold, there's no current flow, so the chassis would be isolated from the AC line. A DPST on/off switch would be cheaper and easier, though.

Rob

Regardless of what the author was thinking, it's still not safe and can't be made safe. You have to wonder whether people wrote in after reading the article, and a later statement was published regarding how unsafe it really was.

There's a good chance you will be, if you build that thing.

Speaking of using the wrong tube for a rectifier, I was recently surprised to find radios that used the type 37 audio triode as the power supply rectifier. They also used resistor power cords dropping 90 volts to run four 6 volt tubes. They must have been the definition of "curtain burner".

Jay

You can design something cheaply, and it might marginally work well enough to sell. The worst case I ever saw was a set using two top cap tubes like a 78 as rectifiers and they had one side of the AC line connected directly to the metal tube caps and their clips. You wouldn't think some of that stuff could have legally been sold, but this was apparently before the UL cracked down on the smaller independents over safety considerations.