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Old 10-22-2020, 10:14 PM   #7
beetle1303
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Default Re: Tefal GV8962 Pro Express steam iron - no power

Quote:
Originally Posted by budm View Post
I trace out the board layout for the SMPS Buck converter section:
One end of R4 is connected to Line, it looks to be used as fusible resistor so it will be low Ohms resistor, another end of R4 is connected to rectifiers D1 which is connected in series with D2, the output of the rectifier is filter by filter cap C5 to give DC Voltage to run SMPS IC U1.
You need to check and see if the internal power MOSFET inside U1 is OK or not, also check D1 and D2 RESISTANCE in both directions.

If SMPC IC input shorted to output (shorted internal MOSFET), it will dump high Voltage (over 300VDC) to C2 and blow up the cap.

Here is the sample circuit of the SMPS Buck converter.
https://ar.pinterest.com/pin/621848661029499082/
D1 & D2 both read ~703ohm one direction. Since D3 now reads 570 off circuit, so mostly likely is this LNK304 shorted? How to test to confirm?

Also, I have no access to the PCB right now, I can't find R4 in those pics that I sent.. Can you point it out please? Thank you.

**edit: do you meant R1 in the picture?
Attached Images
File Type: jpg R1.jpg (305.8 KB, 7 views)

Last edited by beetle1303; 10-22-2020 at 11:27 PM..
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