control unit-power supply not working after a while

where is the problem?

  • temperature problem

    Votes: 1 100.0%
  • capacitor problem

    Votes: 0 0.0%
  • filter problem

    Votes: 0 0.0%
  • other problem

    Votes: 0 0.0%

  • Total voters
    1

Thread Starter

koutselio123

Joined Mar 11, 2017
8
I have in my businness(mill) a PCB (control-power supply)which takes 24v Dc and switch it in a LM2575-T5 switch regulator and also use 24v to make 12volts,in order to give orders to the system tod do many jobs and also power to a cell(i do not know the exact voltage there).The system works but after a while stops.Some times burn the lm2575 and after i change it works again for a while and the same problem.I check capacitors near lm2575 are ok.Do you have any idea what is going on,I load a photo of the PCB.Thanks.
 

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Thread Starter

koutselio123

Joined Mar 11, 2017
8
Yiassoo!, Measure the output current of the regulator, at full load....
I do not do it but i think you are correct that the output current is higher and burns the regulator, but i can not find which component do this, but the problem it is inside the pcb because with another pcb everything is ok, also as far as i can see the cell load uses the 24 volts-12 volts after another regulator, maybe i make a false, make any proposal to find what is going on
 

ScottWang

Joined Aug 23, 2012
7,070
The pictures are not clear.
How long this happened after you bought it?
Did you measure the output current from the regular?
 

Thread Starter

koutselio123

Joined Mar 11, 2017
8
It happens after 7 years, i do not measure the output current but i am sure it is higher than normal, the question is why? where is the problem?
 

ScottWang

Joined Aug 23, 2012
7,070
If it already working fine for 7 years then the problem was not the original designs, it could be any component has a little shorted to caused the current increasing and over heat.

The pictures was not clear, so I think there is no one can give you a properly answer, if you don't have the mR or uR meter to measure the resistance for each IC or any component which needs the power, the first is to check all the capacitance of capacitor, do they have any current leakage, if your meter have the ERS function then it is better and you also could try to unsolder the Vcc pin of ic and measuring their current and resistances between Vcc pin and Gnd pin.
 

Thread Starter

koutselio123

Joined Mar 11, 2017
8
thanks a lot.i have already measure(esr too)all the capacitors exceptsmd capacitors and are ok.Do you think is a little short between the regulator and the ground?i measure via omhometer and nothing bad.if happends this i can not detect a measurement with ohmometer?
 

ScottWang

Joined Aug 23, 2012
7,070
The first thing is to make sure the +Vcc is +5V and measures the output of regulator, to find out which component will be draw more current is more easier to figure out where is the problem.

The ohmmeter can't measures the ESR(Equivalent Series Resistance) of capacitor, if the ESR more higher then the capacitor will be generate more heat.

The general ohmmeter can't measures the resistance between +Vcc and Gnd for each IC, all the Vcc pins of ic are in parallel, so when you want to measure them on board then you will need the resistance meter, we call the meter as Micro-OhmMeter in Taiwan.

RESISTANCE METER RM3548
.
 

Thread Starter

koutselio123

Joined Mar 11, 2017
8
I have it and with this i measure the capacitors.bur in order to see if a short occurred i use a common voltmeter in ohms.is that correct? can i see small shorts in the circuit with this or i have to do something else?
 

ScottWang

Joined Aug 23, 2012
7,070
Please don't write all the capital in all contents.
ESR Meter.

If you measure the +Vcc is correct +5V then you should unsolder each Vcc pin of ic to measures the current and make sure they are ok.
 
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