How to judge whether the LED is broken inside

Speaking of LED digital tube, I think everyone should be familiar with it. It is an electronic device that can display numbers and other information. Display numbers are often used in modeling, and the method is simple. Many feet feel bad and it is not convenient to control them directly with your hands. There are also professional decoders, but the number of pairs has increased.
Today, let's talk about how to use nixie tube. Look at the internal schematic first. It can be seen from the following two figures that the inside of the nixie tube is composed of many light emitting diodes (LEDs). Because leds have positive and negative electrodes, nixie tubes can be divided into two types, one is a common cathode, the other is a common anode. The so-called common cathode refers to connecting the negative electrodes of all light-emitting diodes together, and the common anode refers to connecting the positive electrodes of all light-emitting diodes together.
At that time, I believe you all know how the digital tube is driven. In fact, it is how to light the bulb inside the LED bulb, just like the common anode digital tube in the above figure. Vcc is the positive value of the power supply, and the following numbers represent the cathode pins corresponding to its internal LEDs from 1 to 8. If the negative pole of the power supply in the vcc is connected to the plug 1, the LEDA will be lit. The lit part corresponding to the nixie tube is the horizontal part at the top.
The same is true for other LED lamps. If the LEDC is turned on, the VCC also needs to be connected to the positive pole of the power supply. Pin 3 is connected to the negative pole of the power supply. The corresponding nixie tube is turned on at the lower right corner. If it is found that the corresponding LED does not light up during operation, while other LEDs light up normally, it can also be judged whether the LED interior is broken, and the number of digits that the corresponding nixie tube can display normally will be limited.
Of course, each diode inside is independent of each other. Therefore, in addition to lighting one diode inside, multiple diodes can be lit at the same time. The VCC is the positive pole of the power supply and does not need to move. Just connect the corresponding LED negative pole pin to the negative pole of the power supply at the same time, so that the required number can be displayed.
Take this picture (above figure) again. If you want to display the number 1, you need to light LED 2 and LED 2, 3 at the same time. In actual operation, connect the VCC to the positive pole of the power supply, and connect pin 2 and pin 3 to the negative pole of the power supply. If the nixie tube works normally, you can display the number 1. The following picture is taken by me in actual operation.
Although we take the common anode as an example, the same is true for the common cathode. If you can light LEDs, it is easy to understand the corresponding principle of driving the nixie tube. The most troublesome thing here is that the bought nixie tube does not know which diode corresponds to each pin, or even whether the nixie tube is a common cathode or a common anode. But that doesn't matter. We can use the diode on the multimeter to distinguish these pins.