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Anybody havw any experience in repairing these units. The problem I have lies in the power supply. Can't get the pfc circuit to work. I have replaced pfc ic and mosfet. Help!!
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Link us a schematic?
First thing I check in SMPS is for shorted rectifier diodes on the secondary side.Education is what you're left with after you have forgotten what you have learned. -
In the case of the PFC, also check any components around the MOSFET gate, the current sensing resistor and the boost diode.
MOSFETs can fail with a short between gate and drain, taking out the controller chip and any resistors and diodes used to shape the gate drive.
The current sensing resistor is in the fault current path for a blown MOSFET, and if it fails open it can take the controller chip out.
The boost diode is the most highly stressed component in the whole SMPS. For supplies of a few hundred watts and up, it'll be a TO-220 or TO-247 package on a heatsink. If it fails either short or open, it'll take the MOSFET out with it.
As usual with SMPS, if you miss one bad part, it can take out the whole lot again when you power up.
Without a schematic we can't be more helpful.
"Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"Comment
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