Blinking 21 times power red LED

You need a service engineer

SOLVED: blinks the red light 10 times frequently - Sony Bravia ...

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Apr 24, 2018 - @hdcifix215 10 blinks apparently is not a real error code from Sony. The descriptor for that is "Watch Dog Timer used to track micro processors, ... 2 answers
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SOLVED: red led blink 7 times - Sony KDF-E60A20 ...
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bravia has no picture or sound and flashing 5 times ...
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Hi Darryl mclellan, because of the amount of flashes, it is very possible failure in the system of LEDs of back lighting or the circuit that feeds it

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 section 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 procedure, to many popular brand TVs and other devices.
http://electro-medical.blogspot.com/

If blinks continue without any pause, the main board is faulty.

Sony Bravia TV kdl- red blinking led light error codes ...

? 10:28
https://www.youtube.com/watch?v=0KGysXbxnaU
Mar 28, 2015 - Uploaded by Tampatec
Sony Bravia LCD TV KDL models red blinking led light error codes & possible ... with perfect picture, no warning signs and it just shuts off. is it that quick? ... with the following problem: I connect the power grid lights Standby red light. ... the title before deleting, it is very fast after that flashes Standby 6 times.Missing: 46w3000 ‎30

These may help - the first just tell what it is and which ICs maybe the problem (quite technical)
Solved Sony Bravia Blinking Code
Bravia KDL46EX720 Red LED blinks 4 times and TV wont turn on What is the...
or, in the last resort you could try Sony support, either to get a service manual, or to ask a technician. Don't be fobbed with an expensive answer as in one the examples above.
Support for LCD TV BRAVIA Sony

18.November.2015

Re: Bravia KDL46EX720. Red LED blinks 4 times and TV wont turn on. What is the problem?

Do a Power Reset.

1. Turn off the TV.
2. Unplug the power cord of the TV from the electrical outlet.
3. Let the TV remain without power for 60 seconds.
4. Plug the power cord back into the electrical outlet. (If the television is plugged into a power strip or surge protector, remove it from the power strip or surge protector and plug it directly into the wall outlet. If the issue is resolved, the problem is with the power strip or surge protector and not the television.)
5. Turn on the TV.

If the issue still persists after performing power reset, that may be an indication that the TV needs service. You may refer to this link to locate the nearest Sony authorized service center in your area.

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 section 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 procedure, to many popular brand TVs and other devices.Viewing it in "Mosaic" or "Sidebar" will make surf easy.
http://electronicshelponline.blogspot.com/
Blinking codes details to many popular brand TVs are given.Surf the site with patience.

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 procedure, to many popular brand TVs and other devices. Viewing it in "Mosaic" or "Magazine" will make surf easy.
http://electronicshelponline.blogspot.com/
Blinking codes details to many popular brand TVs are given. Surf the site with patience.

SONY BRAVIA 55EX720
2 lights blinking.

You can try unplugging it for a while and then plugging it back in, but according to the manual, the standby LED:
Lights up red when your TV is in PC power saving mode. If the LED blinks in red continuously, this may indicate the TV needs servicing.
(Operating Instructions, Page 22)