[SIZE=12px]As an update, I found that the standby IC (IC502) was indeed shorted. I replaced it, the connecting resistor, and the MOSFET drive IC (U600). Solder joints were also tidied up. The good news is that when I plug in the isolated PSU, I get no blown fuses/components/etc. I'm also getting a very steady 5.01V DC from the standby output pins (no voltage from anything else). The main 2 caps are humming very, very slightly and being charged/discharged at a steady 167V DC.
So, everything at first looks to be working. Unfortunately, the PSU fails once connected to the other boards....
cmlewis89
Member
Last Activity: 10-12-2024, 04:34 PM
Joined: 09-01-2024
Location: Cincinnati, OH
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Thanks [USER="57756"]R_J[/USER] and [USER="71977"]nomoresonys[/USER] for the replies.
Yeah, I figured that IC must be bad since it's directly connected to a resistor that shorted (just didn't know how to go about testing). I measured the resistance between pins 3 & 4 on IC502 and got 1.3 Ohms.
The one MOSFET was shorted both drain ~ gate, and drain ~ source (the other MOSFET was fine). I'm still testing all the nearby components - don't see any obvious problems yet. Probably a very basic question, but would the drive IC be the one on the underside...Leave a comment:
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LG 47LB5DF blown power supply board
Hi folks,
I'm new to this forum. So my trusty 17-year-old LG 47" LCD recently died. As I was booting it up, I heard a hum followed by a loud bang, sounds of pieces flying around, and loss of power to the unit. Inspecting the PSU, I saw two obvious problems: a blown thermistor (bang + flung pieces) and a visibly bulging main cap. Inspecting as many components as I could with my Fluke MM, I diagnosed that the following components on the "hot side" of the board were also bad: one of the 2 main MOSFETs, main 8A fuse, small cap (25V 47uF) connected to main caps, and a blown... -
Hi all,
My name is Chris and I'm looking to learn how to fix old TVs and other electronics. I tinkered with electronics and basic repairs growing up, and now hope to challenge myself with more advanced projects.Leave a comment:
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