Simple display driver for mechanical television. Between 1928 and 1931, a video amplifier consisted of three tubes. (See 1928 schematic.) I wanted to accomplish the same function with three transistors. Better still, two of the transistors would be in one Darlington package. After I tinkered in the shop for a few days, the project worked!

My circuit provides the entire video electronics and the video display for a mechanical television receiver. See the block diagram above. Build my circuit, and you'll have the equivalent of diagram blocks 2, 3 and 4.

SPECS

• My display consists of four series strings of three LEDs each.
  
  
• A high-gain, PNP preamplifier provides a substantial voltage boost.
  
  
• A Darlington power transistor drives the display.
  
  
• The circuit is entirely direct coupled. (Direct coupling is necessary to avoid phase shift, especially since I don't clamp the DC.)
  
  
• Total circuit current is in the neighborhood of 160 mA.
  
  
• Each LED string handles 40 mA peaks.

• The circuit input source is a CD containing narrowband video. The NBTVA sells such CDs to club members. See the sidebar for a link to the NBTVA.
  
  
• With this amplifier, a "Walkman" type CD player can drive the display. To reconstruct the picture, scan the display with a Nipkow disc.
  
  
• The gadget works like a champ. The contrast range is broad, and the pictures should be acceptable.
  
  
• As with the 1928 Daven circuit that inspired my design, picture sync is up to you. This circuit has no effect on sync.
  
  

My inspiration: 1928 video amp and driver by Daven.

Click... Explanation of mechanical TV block diagram

Go to Page:   1   2   3   4   Next

---

RETURN TO TOP

HOME

CONTACT CURATOR

LINKS

ABOUT THE HOBBY

WHAT WAS MTV LIKE?

AMPLIFIER DESIGN

---

Web www.hawestv.com