Definitive shorted turn. The component is junk.
After assembly, .
Because inductors can produce high-voltage spikes (back EMF) when pulsed, the schematic includes clamping diodes. These protect the sensitive ICs from being fried by the very component they are trying to test. Component List for the Schematic blue ring tester schematic diagram exclusive
Whether you are repairing a vintage arcade monitor, a high-end audio amplifier, or an industrial power supply, this tool will save you hours of guesswork. Build one. Keep it on your bench next to your multimeter. And when a junior technician asks, "How do you know the transformer is bad?" you can smile and say, "I heard its ring." Definitive shorted turn
| 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 | Because inductors can produce high-voltage spikes (back EMF)
SMPS transformers often fail with a single shorted turn due to overheating. The resistance change is immeasurable with a DMM. The Blue Ring Tester detects this in seconds.