26-07-2015, 08:56 PM
I used to repair 700W SMPSUs that fitted in printers thae were as big as large filing cabinets. The boards cost £500 each.
What the board manufacturer had done was to fit 4 FETs on opposite sides of the heat sink with two thin screws and holes so that the insulators got crushed.
They used to blow all the FETs apart and randomly blow cmos chips and diodes all over the place. I had to check everything.
Once I realized what was going on I ordered some of those FETs with insulated tabs and countersunk the holes that still had sharp edges.
The new FETs were a quarter of the price of the originals and they never came back under warranty.
What the board manufacturer had done was to fit 4 FETs on opposite sides of the heat sink with two thin screws and holes so that the insulators got crushed.
They used to blow all the FETs apart and randomly blow cmos chips and diodes all over the place. I had to check everything.
Once I realized what was going on I ordered some of those FETs with insulated tabs and countersunk the holes that still had sharp edges.
The new FETs were a quarter of the price of the originals and they never came back under warranty.
