Crt Clock Schematic -

Looking at the tube socket (e.g., B7G for 3RP1):

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.

Since there is no framebuffer, letters (H, M, S, AM/PM) are drawn using stroke fonts. The ROM stores sequences: Crt Clock Schematic

// Lookup table for digit '0'
int zero[5][2] = 0,0, 10,0, 10,20, 0,20, 0,0;
void drawVector(int x, int y, bool draw) 
digitalWrite(Z_AXIS, draw); // Turn beam on/off
delayMicroseconds(2);       // Settling time
analogWrite(X_DAC, x);
analogWrite(Y_DAC, y);
delayMicroseconds(20);      // Deflection speed

The schematic requires a fast comparator. The microcontroller sends a "BLANK" signal (5V logic).

Because the CRT grid/cathode is at high voltage (-20V to +10V), you need opto-isolation or a level shifter. A common topology uses a 2N3904 transistor pulling the cathode down relative to the grid. Looking at the tube socket (e

Pro Tip: The Z-axis must be fast. If your amplifier is slow, the beam will glow dimly during retrace, creating "ghosting" on the clock face.

CRTs require multiple voltages.

A beam that is always on creates a confusing web of lines connecting the numbers. To draw clean shapes, the schematic includes the "Z-Axis" or "Blanking" logic.

This section is often overlooked but is critical. It is a fast switch that controls the intensity of the electron beam. By tracing the Z-line on the schematic, you see it connected to the logic that detects when the beam is moving between digits. When the beam needs to jump from the end of the '1' to the start of the '2', the Z-logic pulls the intensity line low (blanking), turning the beam off so it doesn't scribble unwanted lines across the screen. The schematic requires a fast comparator