Schematic — Crt Clock

You need two identical copies of this circuit: one for X (horizontal) and one for Y (vertical).

: CRTs require high voltages to function, typically between 300V and 1200V depending on the tube size.

: Often utilize specific vacuum tubes (like the EF80 ) to drive the horizontal and vertical deflection plates. Top Performance Features

. Unlike standard TVs that use magnetic deflection, these clocks use electrostatic deflection

Maintain a minimum clearance of 2.5mm per 1000V between high-voltage traces and low-voltage digital components. Use isolation slots (physical routing cuts in the PCB) underneath the high-voltage sections. Crt Clock Schematic

+150V DC | [R3] 22k 2W | DAC Out ---[R1]---+---+-------------------> To CRT Deflection Plate (+) (0-5V) 10k | | -| | LF351 / | [R4] 1M Op-Amp | | | +---+---|-------------------> To CRT Deflection Plate (-) \ | | ->| | | | [R2]--+ 10k (Feedback Loop) | -150V DC

Two independent Digital-to-Analog Converters (DACs) are required—one for the X-axis (horizontal) and one for the Y-axis (vertical).

A curious journalist came one rainy afternoon and interviewed Mira. She asked where she had found the schematic. Mira told the story she had told herself: that the paper had been in a box of discarded manuals, a relic of a past inventor with a poet’s hand. The journalist smiled and asked the question everyone wanted answered: Did it actually remember? Mira answered in the only way she could—by handing him the cracked photograph someone had left the week before. He held it under the glow and watched the beam draw a loop, then stop in the center. "What does it say?" he asked. Mira felt, for an instant, the strange modest pride of someone who had repaired a clock and found that it kept not just time but tenderness.

+1000V to +2000V to pull the electrons toward the face of the screen. You need two identical copies of this circuit:

To prevent image distortion and keep the beam focused, the schematic must drive the deflection plates symmetrically. For example, if plate X1 goes up by 50V, plate X2 must drop by 50V. 4. The Power Source: High-Voltage Power Supply (HVPS)

Whether your CRT uses electrostatic deflection (like an oscilloscope tube, e.g., 3BP1) or electromagnetic deflection (like a small camcorder viewfinder CRT), the 0–5V DAC signals must be amplified. For electrostatic CRTs, the beam is deflected by high-voltage differentials between two plates.

When drafting your schematic, component ratings are highly critical due to the presence of high voltage. Circuit Area Component Type Recommended Spec / Part Number Switching MOSFET IRF840 or CoolMOS (500V-800V rating) Drives the inductor/flyback transformer HV Multiplier UF4007 (Ultra-fast, 1000V, 1A) Rectifies high-frequency HV spikes HV Smoothing Capacitors Ceramic Disc or Polypropylene (1kV - 2kV) Filters ripple out of the anode supply Deflection BJT Transistors MJE340 (NPN) & MJE350 (PNP) High-voltage video amplification Timekeeping Temperature-compensated clock 4. Safety and Troubleshooting Guidelines

The core architecture of the schematic is divided into three distinct voltage domains: the low-voltage logic section (5V DC), the medium-voltage analog driver section (±12V to ±50V), and the high-voltage section (approx. 1,000V to 1,600V for the anode and focus grids). Successfully reading a CRT clock schematic requires understanding how these three worlds interact. Top Performance Features

Unlike standard television tubes that use magnetic deflection coils wrapped around the neck of the tube, most DIY CRT clocks utilize small . These tubes, such as the ubiquitous 3RP1, 5BP1, or the Soviet 13LO3I, contain two sets of internal plates (X and Y) that steer the electron beam via high-voltage electric fields rather than magnetic ones. The schematic of a CRT clock revolves entirely around controlling these plates.

Building one requires a solid understanding of high-voltage safety, analog deflection circuits, and microcontroller programming. This comprehensive guide breaks down the complete architecture and schematic design of a vector-based CRT clock. 1. System Architecture Overview

: The tube itself, which includes the heater, cathode, control grid (G1) for brightness, and focusing anodes. 2. Power Supply Schematic Details

No CRT clock schematic is complete without the daunting high-voltage (HV) section. Unlike a TV, a small oscilloscope tube does not require 15kV, but it still needs roughly 1,000 to 1,500 volts on the anode to accelerate electrons to sufficient speed. The schematic will show one of two topologies: