Below is a of the classic Blue Ring Tester. Components are arranged for clarity.
The circuit counts how many oscillations exceed a specific voltage threshold. Each "ring" lights one LED in the sequence. Purchasing Options blue ring tester schematic diagram exclusive
The original design commonly utilizes a CD4015BE (dual 4-stage static shift register) or similar logic ICs to handle the sequential activation of the LED display. Below is a of the classic Blue Ring Tester
: Because different transformers have different native Q factors, it is often best to compare readings against a known good component . Each "ring" lights one LED in the sequence
The Blue Ring Tester is a simple, low-cost device that applies a short pulse to a coil and then counts the number of decaying oscillations (ringing). A good coil will produce many oscillations; a coil with a shorted turn will produce very few because the short absorbs the energy.
: The tester uses pulses of approximately 600mV or less, allowing for many in-circuit tests without damaging sensitive semiconductor junctions.