Author Topic: need help in repair\testing of this smps  (Read 1348 times)

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Offline stoica adrian

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need help in repair\testing of this smps
« on: November 07, 2015, 05:50:11 pm »
I have this telekom smps. When i power it up, the line fuse blows. I use an autotransformer for a slow power it ( is the same problem without autotransformer). When my voltage is at around 110V, i can see how the internal relay from the smps are closing, and then a large current is absorbing frome the line blowing the fuse of the line smps  ( 4-6A at the autotransformer ampermeter) . The question is .. what can i use to limit the current, there is something special fore a start up of this kind of telecom power supply?, because i appear that this kind of smps are used along a controller, and ja, i dont have that controller.I dont have a lot of experience in repair this kind of smps. i am electronics technician at my background. Thank you all for the support

Obs- i measure all the components, i don't find a problem with them
« Last Edit: November 07, 2015, 06:10:24 pm by stoica adrian »

Online tautech

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Re: need help in repair\testing of this smps
« Reply #1 on: November 08, 2015, 07:33:40 am »
I'm no expert with SMPS but there are few basic steps that can help with trouble shooting.

No particular order:
1. Identify controller and find datasheets, often "typical application" examples are closely copied by manufacturers in their designs.
2. Power on with a Dim Bulb tester in series with the mains supply, it will limit inrush current are preserve fuses. Google it.  ;) You set the supply current value by selection of the bulb wattage.
3. Power only the controller from a bench PSU and check for the correct waveforms without risk from mains voltages.

Simple failures you should check for:
Resistor/s, or chain of, that supply current to the controller from rectified mains for startup.
Local bulk cap to the controller, ~20-50 uF, gone high ESR or drifted in value.
Flyback diode that supplies controller operating current for continious operation.
UVLO values
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