hi
i have a SMPS and it has a problem that out the voltage drops shortly after power-up , there is no optocoupler is present , i checked all the component using multimeter, some component were removed from one side specially capacitors , but not found any issue. can anyone help me to find this issue.
Thanks

 

Did you check the components in circuit?, are you sure all are OK?, especially transistors?
Why not try test out if circuit?

 

Looks like the fuse is shorted with a piece of wire, which means it has had an issue that pulled a lot of current.

 

Did you check the components in circuit?, are you sure all are OK?, especially transistors?
Why not try test out if circuit?

thanks for advice already tested the components but there was no issues found. but most components tested on board since i need to find the exact issue area , transistors were ok , already tested.

 

Looks like the fuse is shorted with a piece of wire, which means it has had an issue that pulled a lot of current.

ah , no it was replaced by me AC path almost ok. 230V*1.44V im getting out from the capacitor.

 

thanks for advice already tested the components but there was no issues found. but most components tested on board since i need to find the exact issue area , transistors were ok , already tested.

Maybe bad switching ic?
Resistors in area of primary coil of transformers are OK?

 

yes

Maybe bad switching ic?
Resistors in area of primary coil of transformers are OK?

Yes , that was ok

 

yes
Yes , that was ok

How did you know that it's OK?