Schematic - Crt Clock

When moving the beam from the end of the minute hand to the start of the second hand, the Z-axis must be turned off before the DAC changes value. A 1µs delay is required; otherwise, "flyback lines" (ghost diagonal streaks) will appear across the screen.

Author: AI Research Desk Date: April 13, 2026 Subject: Embedded Systems / Retro Computing

This is the most complex region of the schematic. How does one turn the binary number 0010 (the digit '2') into a voltage that deflects an electron beam? Crt Clock Schematic

The schematic reveals a Character Generator subsystem. In discrete designs, this often takes the form of a Read-Only Memory (ROM) chip or a complex arrangement of logic gates (an "AND-OR" matrix).

To move the beam to the corner of the screen, the deflection plates require a differential voltage swing of roughly ±50V to ±100V. Your microcontroller outputs 0V to 5V. You need an amplifier. When moving the beam from the end of

Based on a typical electrostatic CRT clock schematic (e.g., "SNTP-CRT" by David Forbes), here is what you need:

| Section | Critical Parts | Value/Rating | | :--- | :--- | :--- | | HV Supply | Ferrite core (EE25), IRF740 MOSFET, UF4007 diodes | 1.2kV out, 30kHz | | Focus/Bias | High voltage resistor chain (10MΩ + 5MΩ trimpot) | 1W, 3kV rating | | Deflection | APEX PA94 or discrete (BF869/BF870) | +/- 100V @ 50mA | | DAC | MCP4922 (12-bit, dual) | SPI interface | | MCU | Teensy 4.0 or STM32F103 | 72MHz+ for vector speed | | Power | 6.3V AC transformer (for heater) + 24V DC supply | Galvanic isolation | A CRT clock schematic lives or dies by

A CRT clock schematic lives or dies by its deflection amplifiers. A CRT is an electrostatic device (in most oscilloscope tubes). Plates inside the tube physically bend the electron beam.