Hello guys. The 3 yr old office UPS blew one night and I was asked to look into it. It is a Singapore made Giant unit Model 1200 VA. There are 2 banks of FB50N06 power MOSFETS (push-pull circuit?). Each bank has 3 MOSFETS. One bank had 2 of the 3 MOSFETS blistered and burned. The middle one even had its Source pin melted. The two 12 volt batteries were dead.
Nothing else looked cooked and the main AC fuse was intact. I would want to ask what parts to suspect and replace before I change out the burned semiconductors. Thanks in advance.
berniedd
Senior Member
Last Activity: 08-18-2022, 06:39 AM
Joined: 03-19-2007
Location: Philippines
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What to look for that blew UPS MOSFETs?
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Thanks, budm. I haven't gone through the entire board yet, but the power schottky diodes are fine. Of the power transistors Q1 and Q2 (both D13009 NPN transistors) at the right edge of the board, both are shorted. Q2's base resistor R7 is open.
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Re: Schematic needed for XYS-300V-12 power supply
Yeah, a handyman replaced the fuse days before it was brought to me. Of course the new fuse also blew.Leave a comment:
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Re: Schematic needed for XYS-300V-12 power supply
Ok, here it is. For reference, I just flipped the board upside down away from me from the original position as seen above.
The burned parts are C26, C27, R44, R45. A cursory multitester sweep of the boars parts shows that R7 is open, Q2 (NPN power transistor) D13009K is shorted. The main 8ampere AC fuse is open/burned out....Last edited by berniedd; 07-25-2014, 02:55 AM.Leave a comment:
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Re: Schematic needed for XYS-300V-12 power supply
Here you go. Close up shows the 4 burned components whose marks have been removed by the heat. The underside shows nothing unusual, no burn marks and there are no components soldered there....Leave a comment:
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Schematic needed for XYS-300V-12 power supply
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