Testing The Internal High Voltage Diode In Flyback Transformer
A leaky or shorted internal diode in the flyback transformer of a CRT TV or Monitor would cause the set to shutdown upon power on, power blink and even blowing some of the corresponding components like the HOT, B+ FET and B+ coil. Usually if the diode have a direct short circuit it will be easily detect by checking the connection between the anode and the ABL line using analog meter set to X 10 K ohm range. If the diode is leaky then it would be hard to confirm it with the analog meter.
In order to solve the problem you can use two analog meter set to x 10 k ohm and connect the meters like a battery in series an then test from anode to any of the flyback pin. A good diode will usually have only reading. If there is a pin that shows two reading then the internal diode had shorted. It is as simple as that!