What should I do if there is no output of the NES switching power supply?

The reason why the switching power supply always has no voltage output.

This situation is due to the fact that the switching power supply does not oscillate, and the method of further proof is; If the voltage of the rectifier filter capacitor of the switching power supply is turned off after 300V, it means that the switching power supply does not oscillate. The reasons why the switching power supply does not oscillate are:

1) The collector of the switch tube does not get enough working voltage.

2) The base of the switch does not get the starting voltage.

3) The positive feedback circuit element of the switch tube fails.

2. Maintenance methods and steps.

1) Test the collector voltage of the switch tube to 0 or lower than the mains 1 4 times, check the AC 220V input circuit and rectifier filter circuit, if the collector voltage is normal, then check the B pole voltage of the switch.

2) Test the voltage of the switch at the B pole or at the moment of shutdown, use the pointer multimeter R x 1 euro block, the black pen is connected to the B pole, and the red pen is connected to the negative pole of the rectifier filter capacitor (hot ground), listen to the starting sound of the power supply, indicating that the power supply oscillation circuit is normal, only the starting voltage is lacking, and the starting resistance is open or the copper skin is broken. If there is no starting sound, after measuring the BE junction, quickly turn the meter to the voltage gear to measure whether the C pole voltage is quickly discharged. If so, it means that the switch and its discharge circuit are normal, and there are faults in the positive feedback circuit, including feedback resistors, capacitors, freewheeling diodes, positive feedback windings and their switches.

If the voltage at the C pole is still not discharged, it means that the switch and its circuit have an open circuit fault or a short circuit and ground fault at the B pole.

NES is the power code of MEAN WELL.,It means that the previous S series has become NES.,There are too many reasons for no output.,Let's briefly list a few points。

First of all, you have to make sure whether the mains power is input to your power supply, and measure whether the main filter capacitor has voltage or not. If your power supply has a secondary power supply, you should see whether the secondary power supply is started and whether the protection circuit is working, and then look for the problem on the side of the oscillation circuit, so that it will be easier to do it in an orderly manner.

If you need to repair, you can find me, Shanghai Xinxue Technology, all kinds of power supplies can be repaired.

It could be:

The fuse on the input side is blown out;

The switch pipe burned out;

The main control chip is damaged;

The starting circuit is broken;

The output is protected due to short circuits, etc.;

Miscellaneous.

First of all, measure whether the voltage at both ends of the rectified 400V electrolytic capacitor has a +300V voltage, if so, it means that there is no problem with the AC 220V input part, and the fault is in the output pair tube, LM494 or 3525 chip has no output, or the chip does not oscillate, or there is no starting voltage, or the output +24V voltage is high system protection, etc.

I've helped you post on the Big Bit forum for your question, so I'm waiting for a more detailed answer from the master over there. If there is an answer, I will notify you as soon as possible, and you can leave an email. If the question is urgent, you can log in to the forum and search for your title to see other people's answers.

First from the input telecom to the rectification filtering, detection, transforming, voltage stabilization, and segmentation inspection.

There will be many problems with failures, and it is not good to make specific judgments without seeing the real thing.

The principle and maintenance plan of S-150-24 switching power supply can be obtained online. There is no output voltage, which can be repaired by overhauling.

Open the circuit board in the state of no electricity to check whether there are obvious scorched components and virtual soldering on the circuit board. Fuse, rectifier bridge, field power tube, capacitor, etc. are normal, check the starting circuit and starting resistance, most of the faults without output can find the fault point, if you can't find it, you can only check the power on, measure the voltage of several key points, the main capacitor should have a voltage of about 300, the power supply IC384 series of 7 pins or 494 12 pins should have a voltage of about 20V, etc.

What do you want to tune. If it's voltage, there's a potentiometer next to the LED.

It should be that the original coil of the transformer is broken, see if there is any burnout.

Remember to praise and, it is not easy to answer questions, help each other, friends who ask questions on the mobile phone can evaluate the point (satisfied) in the upper right corner of the client. If you.

If you approve of me, please click the (for satisfaction) button in time!!

L and N are connected to the live wire and neutral wire of 100-120V or 200-240V AC respectively, and the terminal with the grounding mark is grounded.

v is the positive pole of the output 24V -V is the negative pole of the output 24V.