There is voltage on the bridge rectifier and main caps (163V). Fuses all check good. One of the smaller electrolytic caps (C9112 which is 50V, 100uF) looked bloated, it measured 60uF with one tester, and defective with another. I replaced it temporarily with same uF rating, higher voltage since I don't have the exact one. I also found that one of the switching mosfets (for lower voltage DC supply I think) was shorted. It is a 50R800CE which I didn't have, but had something with the same voltage and current rating and a similar Rds. None of these fixes helped. I'm out of ideas. Any suggestions what else to check? Any possible sources for a schematic?
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I would prefer to replace with the exact parts but sounds like you may have an open resistor or something, there are quite a few SM components on the reverse side, start tracing from the blown fet, i would suspect U9101 could have taken a hit when Q9101 blew. -
Thanks and yes, I will replace the mosfet with the exact part if I can get it to show signs of life. You were right about an open resistor. The .3 ohm resistor was open. But after replacing that, still no joy. I had to get out the high powered microscope the read the number on U9101. It is SSC3S121A, if anyone else needs to know. Anyway, it is supposed to have 15V on Vcc, at least during startup and I measure about 1.5V. It is not heating up, according to my thermal camera. I will order a replacement U9101, but are there any other parts I should order? I will of course get the correct mosfet.Comment
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Maybe get 2 or 3 of U9101, in case it blows again, check everything in that area all the little resistors and mlc caps if they check out you should be good to go once you replace U9101.Last edited by nomoresonys; Yesterday, 01:03 PM.Comment
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The ic9101 will be damaged for sure, when Q9301 shorted and R9122 opened, 165vdc would have been applied to the OCP pin of the ic.
This link is to a SIMILR power supply that uses the same ic CHINA 715G7574-P01-000-0020 PSU SCH Service Manual download, schematics, eeprom, repair info for electronics experts (elektrotanya.com)Comment
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Awesome, glad you were able to make some progress, be sure to try and get authentic/genuine parts, hope you get it sorted, we all love it when something gets repaired on the component level but as a last resort in case you didn't see it, Tvpartstoday has a package deal containing all the boards for US33 : https://tvpartstoday.com/products/ns...-ns-50f301na24Comment
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Thanks for all the help, you guys! I will order the parts tomorrow and if I get it working, I will donate it since Best Buy is replacing the old one under warranty. I also hate to see things go to the landfill.
BTW, I can't believe they sell all 3 boards for only $33. It may be a wash buying the boards, vs. the parts I need.
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Looks like I will buying the repair kit instead of indivicual components because I can't find U9101 (SSC3S121A) from the usual suspects (Mouser, Digikey). Will post back here when new boards are installed.Comment
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Two U9101 there, looks legit, speed pak shipping, looks like it's SSC3S121 no A on the end. This chip is compatible. The A replaced it, they say the A is new and improved but who really knows: https://www.ebay.com/itm/28401461038...Bk9SR-yO87KUZgComment
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Thanks for the link. Since we can't be sure if that's the right part for U9101, and also since there are other parts that need replacing, I decided to go with a used PS board from Ebay for $21. The kit with 3 other boards could have been a good buy, but with shipping and tax, the total would have been over $60.
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Having a new problem with the 19" Insignia that I modified with one of my automatic turn on circuits. That is now completely disconnected so that is not the issue. I was doing some modifications on that circuitry and managed to short something out on the underside of the power board.
Actually found and bought the service manual (who knew it was even available?!) which brought me to the High Voltage Startup Circuit controller chip.
Looking up that chip number- LD7575APS brought me to the attached datasheet. I have marked my voltage readings on the schematic sheet (open in new... -
This is my first attempt at troubleshooting a board like this, I know I could just buy a new board but I'm curious to figure out how this works. I've been testing different components in the evenings this week and I think the problem is with the IC failing to start up for some reason. When the board is plugged in there is no standby voltage.
Then today it randomly sprung to life like a zombie but shortly died thereafter. I have no idea why it would have done that and its the first time I've seen it running. I discharged capacitors on the board last night, then it was sitting today.... -
Hi. I got a Vizio with no power or standby, and won't turn on with remote or button. I checked the voltages on the connector and all read 0.00V or nearly 0(0.050 ON/OFF pin). None of the pins are labeled STB for standby although I do see some 5V pins. Other than the obvious standby led, which isn't coming on, is there a way to check for standby voltage on this PS. I'm trying to see if my problem is the PS or mainboard. Some Vizios I have fixed with no standby led me to think it was the PS but it turned out being the mainboard. Any experience with this set would be greatly appreciated. -
Hi all.
I started a thread while back regarding TV power supply standby circuitry as it is something I am not quite on top of.
SMPS theory and function is becoming more familiar, however the standby part is still a bit of a mystery.
Anyway, a friend has this TV with the above mentioned power supply board which has no standby voltage, nor any other voltages leaving the board.
The mains AC comes in fine, gets filtered and rectified with power is on the main filter cap as well as the transformer and drain pins of the ICE3B0665J, but that's it.
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When I tried to repair LG 29 inch CRT TV, I found that the ESR value of samyoung SMS capacitor(160v 2.2uf), which is very close to D1879 transistor, is 6 ohm.
Judging from above ESR Meter Table,I think It is necessary to replace this sms capacitor.So I visited local electronics shop,and I purchased 160v 2.2uf rubycon YK capacitor.
But when I browse through rubycon YK datasheet,I found that there is no ripple current rating for 160v 2.2uf specification. But On the contrary, I found 39 mA ripple current rating for 160v 2.2uf SMS capacitor.
Rubycon YK DataSheet (b...
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