My Hisense tv power light is blinking. No picture or sound.

See page 32 of user manual (Quick Problem Solving Tips). Your problem is discussed there.

50A6G-User-Manual.pdf (hisense-usa.com)

A blinking red light on the power button of a Hisense 55 inch model 50R6E3 TV could indicate a problem with the TV's power supply. It could be caused by a malfunctioning component, such as a blown fuse or failed capacitor, or it could be an indication that the TV is overheating. In some cases, a blinking red light can also indicate that the TV's firmware is not up to date and needs to be updated

Hisense Blink Codes

https://techprofet.com/hisense-tv-blinking-codes/

LG Flickering is a known issue

https://www.google.com/search?q=LG+60LB6100-UG+picture+flickers

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Hisense TV Blinking Codes (Flashing Red light Fixed)

https://homespoiler.com > hisense-tv-blinking-codes
Oct 8, 2022 - If it blinks 2, 3, or 5 times, it means there is an issue with the backlight, mainboard, inverter, or power board. On the other hand, if the ...
‎Hisense TV blink codes concept · ‎Fixing the Hisense TV blinking... · ‎FAQ

More here and videos

https://www.google.com/search?q=hisense+tv+3blinks&

However, best advice. Balance how old and if it is time to upgrade. Hisense is a budget brand.

https://www.fixya.com/support/r29790007-repairing_own_television

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1. Why hisense TV red flashing power light has sound but no picture
There could be a few reasons why your Hisense TV has a red flashing power light but no picture. It could be an issue with the TV itself, the power supply, or the input signal. Let's take a look at each of these possibilities in turn.

2. How to fix hisense TV red flashing power light has sound but no picture

If your Hisense TV has a red flashing power light but no picture, there are a few things you can try to fix the problem. First, check to make sure that the power supply is plugged in and that the TV is receiving power.

Next, check the input signal to make sure that it is compatible with the TV. Finally, if the TV itself appears to be the problem, you can try resetting it.

3. What to do if hisense TV red flashing power light has sound but no picture

If your Hisense TV has a red flashing power light but no picture, there are a few things you can try to fix the problem. First, check to make sure that the power supply is plugged in and that the TV is receiving power.

Next, check the input signal to make sure that it is compatible with the TV. Finally, if the TV itself appears to be the problem, you can try resetting it.

Hisense only has 10 blink codes, on most brands they're helpful but not as much on Hisense, in 9 out of 10 sets it turns out being backlights, we've had sets before in our shop where an image wasn't visible, but it still turned out being bad lamp strips. Power boards are a bit different on Hisense sets as loss of backlights can put the set in sleep mode leaving only the standby voltage. Best way to troubleshoot the set would be with a backlight tester

If it was an open "internal fuse" the error code wouldn't show!!!... bad advice...

I looked in my Hisense service manuals and 3 blinks error code is LED rail shutdown from over voltage or over current, most likely you have some bad lamps in the panel, you can open the panel up and take a 3 volt power source, like 2 AA batteries and test them one at a time, replace the ones that are bad or its easier to replace the entire strip..Good luck

Those blinks are fault indications. From the number of blinks occur at one time switch on, you can get an idea about the faulty circuit stage inside it. http://electronicshelponline.blogspot.com/ If you wish to get more details visit the site linked here.

Fault to its main board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. http://electronicshelponline.blogspot.com/ . In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit stage inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power led, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating, to many popular brand TVs and other devices. Viewing it in "Mosaic" will make surf easy.
http://electronicshelponline.blogspot.com/
Blinking codes details to many popular brand TVs are given. Surf the site with patience.