Blue Ring Tester Schematic Diagram Exclusive Fixed Jun 2026
The original and most comprehensive schematic for the Blue Ring Tester can be found in the assembly manual for the Dick Smith Electronics K7205 kit and its subsequent iterations, such as the one sold by flippers.com. To view the full, original schematic diagram in PDF format, please use this exclusive link:
The 555 timer (U1) generates narrow, low-duty-cycle positive pulses (approx. 10µs wide) at a frequency of about 100Hz. These pulses are fed through a current-limiting resistor (R3) to the tank circuit.
Based on documented circuit designs, the tester typically employs the following architecture: Pulse Generation : It applies a low-voltage pulse (approximately ) at a frequency of about to the inductor under test. Logic and Counting
When the pulse is applied to the component under test, it forms an implicit LC (Inductor-Capacitor) tank circuit. The is the device under test. The tester provides the resonant capacitor. blue ring tester schematic diagram exclusive
| Component | Value | Purpose | |-----------|-------|---------| | R1 | 10k | Base bias for Q1 | | R2 | 1k | Emitter current limit | | R4 | 10k | Signal output resistor | | R5 | 100k | Attenuation/filter resistor | | C2 | 100nF | Supply decoupling | | C3 | 1nF | High-pass filter | | C4 | 100pF | Low-pass filter (noise reduction) | | Q1 | 2N3904 | NPN switching transistor | | Lx | Unknown | Coil under test |
Following the above, trace the signal path:
The Blue Ring Tester remains a staple because it finds faults that $500 digital multimeters miss. By understanding this schematic, you’re not just following a diagram—you’re mastering the physics of magnetic resonance. The original and most comprehensive schematic for the
The Blue Ring Tester is the gold standard for testing high-Q inductive components. It accurately identifies shorted turns in flyback transformers, deflection yokes, and switch-mode power supply (SMPS) transformers.
Even a reliable tester can malfunction. Common issues and fixes include:
The design below is an optimized, discrete-logic variant of the classic Dick Smith Electronics (DSE) K-7205 kit. It utilizes a highly stable LM393 voltage comparator to digitize the analog ring pulses and an LED bar graph driver to display the results. Circuit Layout Description These pulses are fed through a current-limiting resistor
Detects the ringing amplitude.
Standard ohmmeters cannot detect a single shorted turn in a winding with high resistance. The ring tester can.
The required components are few, easily available, and low-cost. Here's a typical bill of materials for a DIY project:
