Mon, 15 Nov 2021

samsung 245T monitor power supply repair

I've been using a pair of Samsung 245T monitors since 2008 (13 years!) and I really quite like them, something about the 16:10 aspect ratio that just feels right. They were very expensive monitors at the time, but they have really lasted quite well since I use them pretty much every day. Recently I had an issue where one of them would not power on very reliably. This started happening a few months ago, and my solution at the time was to plug it into a UPS so that it would not ever power down which worked for a few months. Plugging it in and powering it on with the power button on the front would just not respond. Eventually if you left it for a while and got lucky, as you hit the button it would power up and work just fine until loosing mains power again. It would go to sleep just fine and wake up from that, but if it lost power it would not power back on reliably. Anyways, this finally happened where it got powered off and I just couldn't turn it back on again. I took a little time and disassembled it and tried a few things. I gave it the heat treatment hopeing to reflow the boards to maybe fix the issue but no luck there. I didn't see any visible issue on the power supply board, but decided to try replacing a few caps to see. Initially I replaced the larger caps on the DC power supply side but that also didn't help. After a bit reading into power supply design, I came to the conclusion it might be the small standby power supply that is used to sort of bootstrap the power supply. So I replaced the caps around the little IC that handles this and controls the switching for the main AC to DC conversion. This seemed to work. In the end I replaced the 6 capacitors from the board highlighted below. These wre 50V 22uf and 50V 2.2uf caps, which I swapped out with some slightly larger caps that I had in and around those ratings. The monitor power powers up perfectly now and is back up and going.

/blogimages/20211115/power_supply.jpg

posted at: 22:41 | path: /electronics | permanent link to this entry


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