No +5V for a switching mode power supply

[sdancer75]

A power supply (SMPS) outputs four dc voltages but one of them the +5 V have less than 2 V. The question is what component is responsible for the wrong output? What should I look for to fix the problem? Any recommendations ?

Voltage output : +5, +11, +19.8, +24

Current output : 0.15, 4.5, 0.5, 1.0A

Freq range : 50-60 Hz

Main components of the PCB

• A1015 (LOW FREQUENCY AMPLIFIER)
• C1815 (Audio Frequency Amplifier & High Frequency OSC)
• HA17393 (Dual Comparator)
• K2545 (DC−DC Converter)
• FES8JT (Ultrafast Plastic Rectifier)
• RS401L (BRIDGE RECTIFIER)
• UC3842B-D (High Performance Current Mode Controllers)

 

[kellys_eye]

Did you load the outputs prior to testing? Such PSUs usually require a minimum load in order for the regulation circuitry to kick in. Is there a separate regulator device for the 5V output? If so, it could just be a simple matter of replacement.

 

[sdancer75]

Did you load the outputs prior to testing? Such PSUs usually require a minimum load in order for the regulation circuitry to kick in. Is there a separate regulator device for the 5V output? If so, it could just be a simple matter of replacement.

Hi,

Yes, I load the output but one of them each time (not all simultaneously). I did see a seperate regulator 5V device.

 

[kellys_eye]

If the 5V is down then change the regulator.