Varying low output of a power supply

[dilshandcs]

I have 12V switch mode power supply. Now it shows pulsating voltage between 4V and 7V which is continuously switching between those voltages? Can you help me?

 

[MrTeal]

I have 12V switch mode power supply. Now it shows pulsating voltage between 4V and 7V which is continuously switching between those voltages? Can you help me?

Get a new one. Unless you have a large amount of experience with these things it won't be cost effective to repair, and even if you do it's not worth the risk of torching the rest of your components.

 

[dilshandcs]

I have a 12V output smps. recently it is damaged due to a lightning. So power supply was not worked(No output).. I checked the all the components in the circuit including the capacitors and replaced them. I could find one zener diode was not worked. And also it has been damaged. Even the value of the zener can not be recognized. So I guess a value and put a 15.3V zener to it. Then the power supplied was worked and the output was 7V (not 12V). Then I searched some diagrams in the internet and put a 11V zener diode. Then the output is started varying between 4Vand 7V continuously (pulstating). All the components in the power supply is good, So i think problem is with this zener. Please help me to solve this trouble. Because this is a inbuilt power supply of another circuit.