Green Power BP430A – ATX PC Power Supply Repaired

By on September 5, 2013



powersupplyrepairing

powersupplyrepair

This pc power supply was completely dead and with electronic knowledge that I received from this eBook: TROUBLE SHOOTING AND REPAIRING Switch Mode Power Supply ( by: MR Jestine Yong) I started to repair it.

After opening the unit and blowing off the dusts, I found 5 electrolytic caps that were bulged. From the picture the electrolyte liquid were boiled inside the cap due to heat and then came on the top and dried there.

power supply repair

power supply repair

There were many cold solder joints in the PCB board. The bridge rectifier and fuse were good

power supply repair

In the above picture, the solder joints could only be resoldered with the help of flux liquid.

(Special thanks to MR Jestine YONG for good suggestions)

I also found 6 Toroidal coils/inductors that were good. Two were installed at the AC supply input area and the other 4 were at the secondary side (DC output).

toroidal coils

At secondary side of SMPS, I found one of the 4 Schottky diodes SBR 4060 PT (60 VOLT 40 Amp) was shorted when tested with analog Multimeter set to X 10 K ohm

schottky diode

This Power supply unit has three SMPS  transformer  for 5+ 12+ 3.3+ volt and all were tested good with my blue ring tester

blue ring tester tested the transformers

The control IC TL494CN was found to be good after tested the output signal (square wave) with an oscilloscope.

power supply repair tl494cn

scope to check power supply

Then I perform a test with 100 watt bulb .  First I removed the fuse, solder the light bulb wires across the fuse terminal then connect the terminals to the ATX power supply tester. After plug in the power supply the light bulb first started to glow then became very dim

 

pc power supply repair

power supply repair pc

As you can see all the voltages more or less the same except stand by +5 volt (5VSB) that is 5.8 volt which is more than the rated value (4.75-5.25 volts).Then I removed the bulb and reinstalled the fuse.

I started to check backward from the terminal of 5 +volt (purple wire) to the board.  I found another big Schottky diode. SB540 is a 40 volt 5 ampere diode. It was tested good with analog meter set to x 10 K ohm.

schottky diode shorted

atx power supply repair

IC PS 223

This IC controls the over voltages and under voltages of all outputs and checked to be good. At the nearby area of this IC I found three electrolytic caps to be bad.

1-  10@ 50 volt were tested by ESR METER and it showed open circuit (no ESR value) and capacitance tester showed that it was only 1.5 microfarad.

2-  1 micro farad @ 50 volts also has high ESR value.

power supply repairing pc

I changed all the bad e-caps and the 5 volt stand by voltage was back to normal.

beh

This article was prepared for you by Mr Beh, one of our ‘Master Authors’ from Iran.

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By the way if you have any good repair article that you want me to publish in this blog please do contact me HERE.

 

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One Comment

  1. Ulises Aguilar Pazzani

    November 12, 2015 at 10:13 am

    nice job Mr Beh

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