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Old 06-02-2020, 10:28 PM   #11
Badcaps Veteran
Join Date: Dec 2010
City & State: Alberta
My Country: Canada
Posts: 2,634
Default Re: QW-MS3010D 30V 10A Variable PSU Blown MOSFET

The power supply is a half-bridge configuration with transformer drive to the power mosfets. So shorted mosfets cannot damage the KA7500 (TL494). But the gate-drive resistors, R2 50R? looks be blown and there is another for Q3's gate to check. They are the fuse sometimes. In-circuit you would read a short G-S due to the drive transformer to the IRFP840's.

I have this Mastech HY3030E schematic which I believe is similar enough to understand the circuit.
PWM IC drives 4 transistors which drive the gate-drive transformer.

The low voltage SMPS IC DK112 looks discoloured, I wonder if it works and you have any low voltage DC present?
Note the (Mastech) power suplpy has an SCR which supplies power to the power mosfets only after the little SMPS turns it on.
Attached Files
File Type: pdf Mastech PSU HY3030E.pdf (68.4 KB, 17 views)

Last edited by redwire; 06-02-2020 at 10:32 PM..
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