TV won't start, one problem or two?

[Tim R]

We turn on our Emerson Model LF391EM4F flat screen, (manufactured 2013). The screen shows the Emerson logo, then there's a staticky pop noise and it shuts off.

I tried unplugging it for a bit and plugging it back in. No luck. We've had it for a while, and TVs are dirt cheap now. But here's what seems weird.

I'm teleworking so I have to be on line for work. When I unplugged it, our WiFi stopped. It came back up maybe 5 minutes or so later. Very annoying if you're on a video call. I was pretty sure I hadn't unplugged the cable box or router.

So about an hour later with the family's help we carried up the spare display from the basement and plugged that in. We were very careful to check all the connections and ensure we didn't unplug anything but that TV, and then plugged the other one in, and of course reconnect the HDMI from the cable box. Same thing, WiFi dropped and came back 5 - 10 minutes later.

So, how does the power from the TV affect the WiFi router? The cable connection from Comcast to the router is separate from that of the cable to the channel box. Both are plugged into the same power strip.

[Lisa Court]

Unrelated. Those Funai models behave *exactly* that way when an LED is bad inside the display. When first turned on, the Emerson logo (or Magnavox, Philips, etc) appears with the backlights running at about 70%. When it finishes booting and switches to the input screen, the LEDs are throttled up to 100%. At that point, one of the three LED driver ICs detects either an overvolt or undercurrent condition because of the failing LED, and it shuts down the main board hard, instead of the normal power down procedure, so a pop is heard in the speakers.

You can prove this out by tying the collectors of transistors Q1102, Q1202, and Q1302 together. This will lock the three LED channels together and prevent the shutdown. Running it this way for any length of time will probably cause a burn on one of the LED strips, so don't leave it this way.

[micky]

In sci.electronics.repair, on Mon, 1 Feb 2021 09:40:57 -0800 (PST), Tim

R <timot...@aol.com> wrote:

>We turn on our Emerson Model LF391EM4F flat screen, (manufactured 2013). The screen shows the Emerson logo, then there's a staticky pop noise and it shuts off.
>
>I tried unplugging it for a bit and plugging it back in. No luck. We've had it for a while, and TVs are dirt cheap now. But here's what seems weird.
>
>I'm teleworking so I have to be on line for work. When I unplugged it, our WiFi stopped. It came back up maybe 5 minutes or so later. Very annoying if you're on a video call. I was pretty sure I hadn't unplugged the cable box or router.

This won't help you at all, but I have two table radios, one on top of
another, and when I turn one on, a certain station I listen to on the
other goes totally silent!!