Bought this t.v. said it didn't have sound. I got it plugged in and noticed not only no sound but very laggy display. Kind of like when a computer processor is being utilized 100%. When video isn't playing the menu, apps, and t.v in general work great. A day later trying to diagnose the sound problem I hooked up some external speakers through the RCA out and the tv worked flawlessly with exception of the antenna connection. The discovered channels would come and go every second or so. The next day turned on tv with no changes made and the extreme lag had returned. No sound except through external speakers and very spotty like the video. I gave up, got a main board in and swapped it out. Plugged in and everything worked perfectly. Internal speakers, all inputs and no intermittent digital antenna signal. TV upgraded firmware after being off for an hour or so. Restarted every thing was good still. Next day (today) get home to show the wife and the same symptoms have returned. No internal sound, very laggy picture. Not really sure where to look other than the power board. I've taken voltage readings, but not when the tv was running good.
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Re: Vizio M471i-a2 weird symptoms need help.
Okay while writing this up I was doing some troubleshooting. I found that if I disconnected the IR cable to MB I would get internal sound, but very flaky video. If I connected the ribbon cable while the tv is on (I know not a good idea) and then disconnected again, my video and sound worked fine. So figured it was the ir sensor or the cable. The ribbon cable is marked ir on one end and MB on the other. I flipped the cable backwards and now tv is working great so far. Getting good 3.3v on test points on main board ribbon cable and before was getting cycling 1.2v climbing to 3.3v on one of the pins. Guessing cable might be bad.
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