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[SOLVED] SMPS On board Output Green LED Flashing On and Off Problem?

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nick703

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Hello friends i have a SMPS https://www.electronicscomp.com/rd-...-8a-12v-4a-88w-dual-output-metal-power-supply

It's working perfectly and suddenly its blast on power supply. So i have opened the SMPS and find out there is a Fuse and NTC is blown and also checking other component but didn't find anything else to burn.I have also checked Diode and all is good.
So i have inserted same rating Fuse and NTC and also change Opto coupler ic PC817 of feedback circuit and then start the SMPS but now problem is SMPS output Green LED is flashing On and Off .

So please suggest me what other to i have a check?
 

KlausST

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Hi,

on the picture I can´t find anything defective.

Klaus
 

d123

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Hi,

You need to check what the flashing green led signifies :).

If the fuse blew, maybe a capacitor has gone short and was the cause or was a consequence of something else. They look okay in the photo.
 

schmitt trigger

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Even if a component doesn’t visually appear to have been damaged, it nevertheless can become non-operational by whatever stress caused the fuse to blow.

Time for some trouble shooting, which you need at the very least a DMM; your eyes alone are not enough.
 

nick703

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i have checked all component with multi meter and also capacitor motor but didn't found any problem.

Now checking TL431 ic and side component but that look also good.
ok doing more testing on this.
 

KlausST

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Hi,

The LED usually shows output voltage (please check). If so, then the switcher starts and stops continously.
Then I assume the "switching circuit" (IC, transistor, diode) is working.
How old is the power supply?
A defective capacitor may cause such behaviour.
Are all the capacitor tops flat (not "blown" outside)
Do you see any signs like floid, oil, smoke .. at the PCB underneath the capacitors.

One possible reason may be a defective feedback path.

Klaus
 

nick703

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Actually i have a checked all Capacitor using Capacitor meter and also Their Tops is Flat.

And also i have traced FeedBack Path and didn't find any problem.

And my power supply is 1.5 year old.

i only find problem in Fuse and RTC (NTC) which has blown and i placed new one.
 

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eagle1109

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Also check output rails with DMM in continuity mode with no power on PSU, if you get a short then the output semiconductor could be broken.
 

nick703

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Now Problem is Solved .
Actually the problem is without load connected the green led is Blinking.
But when i connected load SMPS working properly.

I have contacted MeanWell Company and then they suggest me solution.
 

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