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I was given a job order to repair a switch mode power supply made by ELPAC Power Systems of Santa Ana, California, USA just a while ago. This P.S. is used to provide 5VDC at 30 Amps capacity to power digital control cards. 15VDC and 28VDC are also provided by this power supply unit at about 4 Amps capacity.
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Usually, the cause of trouble for this kind of switch-mode power supplies is just calibration and adjustment of the various potentiometers or commonly called 'pots' by electronic technicians for the overload protection, over-voltage protection and under-voltage protection. But i was tweaking the said supply unit for almost an hour, and it just keeps on shutting down enabling its protection.
There was no choice but to open up the unit and check its internals. I traced the circuit from the primary power side to the secondary power side to its feedback and pulse width modulation circuits. All are okay (capacitors, SCRs, resistors, transistors, diodes, etc). The only thing that I haven't checked yet is its transformer. I tried tapping the said transformer with the tip of a screwdriver while the unit is power upped, and just like magic, it released it desired outputs. I tried tapping the transformer again and the unit died down.
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There is only one thing to do. REBAKE the transformer, not rewind because it is just intermittent and could be the coils inside the said transformer might be loose due to time and vibration. I sent it to the Electrical Repair Shop Department of the company where I am currently connected with because they are the experts when it comes to inductors. I requested the said job order and put the ELPAC Power Supply into its pending status.
We'll just wait for the transformer and make any final observations when it is done. For the meantime, i'll just do another job load.
.jpg)
Usually, the cause of trouble for this kind of switch-mode power supplies is just calibration and adjustment of the various potentiometers or commonly called 'pots' by electronic technicians for the overload protection, over-voltage protection and under-voltage protection. But i was tweaking the said supply unit for almost an hour, and it just keeps on shutting down enabling its protection.
There was no choice but to open up the unit and check its internals. I traced the circuit from the primary power side to the secondary power side to its feedback and pulse width modulation circuits. All are okay (capacitors, SCRs, resistors, transistors, diodes, etc). The only thing that I haven't checked yet is its transformer. I tried tapping the said transformer with the tip of a screwdriver while the unit is power upped, and just like magic, it released it desired outputs. I tried tapping the transformer again and the unit died down.
.jpg)
There is only one thing to do. REBAKE the transformer, not rewind because it is just intermittent and could be the coils inside the said transformer might be loose due to time and vibration. I sent it to the Electrical Repair Shop Department of the company where I am currently connected with because they are the experts when it comes to inductors. I requested the said job order and put the ELPAC Power Supply into its pending status.
We'll just wait for the transformer and make any final observations when it is done. For the meantime, i'll just do another job load.