PLC (FATEK) Power supply Board issue

[mjawed]

Dear Friends,

Working on Service & Repairs of the PLC ( FATEK Brand) Model FBs-14MA, with DEAD POWER SUPPLY BOARD ( Bottom PCB).

Successfully, I have managed to make repairs by replacing the NEW SMPS IC NCP1203D6 with the related defective SMD parts and the burnt Bridge Rectifier and FET, and voila, it's OPERATIONAL again.

But, for the another same PLC, after replacing the NEW SMPS IC NCP1203D6 with the related defective SMD parts and the burnt BR and FET, the SMPS voltage outputs only 10V DC, while the actual output voltages are 24V DC. The suspected Optocoupler PC817 is also replaced with a NEW one, but the output volts are the same e.g. 10V DC.
There are no any Parts on the Bottom side of the PCB, as review the picture attached of the BOT side of the PCB for Power Supply Board.
I guess the TL431 / LM341 SMD IC in SOT23-3 Pack is the cause of this issue , sine the 24V DC is the only Output available, as normal operation. I don't have the schematic of this board also.

Need some help to figure out the actual cause for this 10V output instead of NORMAL 24V DC output.

Your help shall be appreciated. Pictures are attached for reference.

 

[betwixt]

Usually when a switch mode supply seems to work but the output voltage is low, the output capacitors have dropped in value or gone open circuit. I have never seen one of these units but my guess would be it is the smaller brown electrolytic (470uF).

Brian.

 

[mjawed]

Hi,
As per your suggestions, I got the POWER BOARD in order with 24V DC output as normal operation.

Now, the IO BOARD with INPUTS & RELAY OUTPUTS has the Missing SMD DC -DC step down converter IC in SO8 pack. I checked the rest of the components, all OK.
Please share the SMD IC part no, if someone here may know.

As looks into the similar FATEK PLC, but other model FBs-14MA with the IO BOARD no FBs-1410-3, the same SMD IC have different pin connections, as checked & compared with each other ( IO BOARDS).
This is the FATEK PLC model FBs-14MAR-AC with the IO BOARD no. FBs-1410-7.

If someone has worked on these PLCs, please share the missing part no.
Pictures for reference are attached.

Always appreciate your help guys. My best Regards to All.