1384 - TI Appnote Clock PWB

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Documents: Schematic (RevA Rev-) / BOM (Rev-) / Assembled / Breadboard

Description:  This is a simple hard logic nixie clock based on a data book application schematic from the mid 1970's illustrating the use of Texas Instruments' 74141 BCD-Decimal nixie decoder-driver IC's.  A few modifications from the original design were implemented:

  •  A 5V series regulator instead of the original zener shunt circuit for powering the logic.
  •  Neon lamp drive for the AM/PM indicators.
  •  Zeroing was added to the line frequency prescaler and 1's digit during setting.
  •  The high voltage transformer input has also been replaced by a boost supply for the anode 170V supply.
  •  An error in the seconds 10's connection between the decoder and display was corrected.
  •  Wires for 60Hz line operation.  Jumpers are provided for configuration for 50Hz line frequency


  •  All through hole parts except the bypass capacitors which are 1206 ceramic SMT.
  •  Pads are provided for either an SMT vertical power connector or a through hole right angle power connector.
  •  Pads are provided for either a 4 pin DIP bridge rectifier or4 single diodes.
  •  HVPS may be jumper selected to be powered via the raw DC rail or from the 5V regulator output (This improves efficiency when a 5V switcher is used in place of the 7805).
  •  Designed for IN12 nixie tubes but this will work with any nixie display:  The cathodes for each tube are marked on the PWB for easy wiring.
  •  Components are labeled with their values for easy assembly.

Input power:  9VAC @ 500mA, suggested AC output wall adapters and connector, listed below are suitable adapters.

  •  CUI EPA090050-S/T-SZ, 120VAC in / 9VAC out @ 500mA (Digikey T1004-ND)
  •  ReliaPro ACU090050, 120VAC in / 9VAC out @ 500mA (Jameco 100061)
  •  Radio Shack 15-1963, 120VAC in / 12VAC out @ 400mA (Jameco 2076543)
  •  Check Marlin P Jones for good deals on adapters


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