Hi, I am repairing the power supply of my video projector and I need to understand what type of diode is mounted here, in the green circle:
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I see that it have three colored rings, but if I decode it with resistor color code I obtain 652, that don't tell me nothing... because the red ring is more width than others, I suppose that the reading is 6522, but I don't find SMD diodes with this coding... this diode is connected between gate and source of power mosfet, that its source is connected to ground through 1.2ohm resistor.
this is a zener diode or schottky diode? :-( thanks for your aid
1N4256 ? Can you identify the exploded 8pin driver? Are the 4 pin devices ,over the isolation slot, opto couplers ? Do you know the failure initiation/progression?
Hi, thanks for your reply, here in Italy nobody is answering me...
the model is EzPro 715H from Optoma
Here some photos of burned power supply:
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the exploded chip I think is an UC3844. With a magnifier lens I can read over an not burnt portion of chip surface the signature "1844A", but I see that the UC1844A is designed for military and aerospace standards, then is probably that the correct device is UC3844A (with 1844A core inside...) the application schematic in the datasheet is very similar to this, except for gate driving circuit This is a schematic that I have drawn down from board:
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The two units over insulation slot are optocouplers In fact, all semiconductors in the primary side is burned or shorted... I don't know if the transformer is good, I have measured impedance and the primary winding is 2,2mH and the winding that supply the controller is about 190uH... The small toroidal transformer was burned, but I have counted windings and I have already rewinded it. I would want to try to repair the entire power supply. I think the fault is born from short circuit in line rectificator diode. The main high voltage supply for the lamp is now working again, and the logic boards of projector is also working. which is the anode in the diode with three rings? is a zener diode or schottky? Thanks again.
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