[GreenKeys] GreenKeys Digest, Vol 110, Issue 51

[John Nagle]

On 3/15/2013 8:07 AM, greenkeys-request at mailman.qth.net wrote:
> On Fri, Mar 15, 2013 at 8:27 AM, Rokumon Cat <rokumoncat at yahoo.com>
> wrote:
>>>> 
>>>> Hi again,
>>>> 
>>>> Does anyone know where I can find a simple, tube only circuit
>>>> for a local loop power supply using something like a 5Y3? I
>>>> need to build four of them in a rack mount for my TTY display
>>>> set up.
>>>> 
>>>> I have found many designs for solid state rectifiers that would
>>>> work quite well, but the point of my demo is to use only tubes
>>>> so that I will have an EMP hardened display using 1950s and
>>>> early 1960s technology.
>>>> 
>>>> Thank you again,
>>>> 
>>>> Joe

    An 0Z4 tube should do it. That's a cold cathode gas rectifier tube.
No filament.  Still available for about $3.  Current rating is 30mA
min, 90mA max,. so it's the right size for a Teletype loop.
Voltage drop is 24V.  Commonly used in car radios of the 1950s. See

     http://www.radiomuseum.org/tubes/tube_0z4.html

for a circuit.  Very simple.  For a Teletype loop you'll want a
center-tapped transformer with about 120-150V per side, not 300V
as shown.

    Realistically, EMP isn't going to blow a power diode. The
junction is far too big.

					John Nagle