No display ,no sounds standby only

Question edited for clarity.

https://www.google.com/search?q=Sony+RV6+that+the+power+button+LED+is+blinking

Service Manual

http://diagramas.diagramasde.com/audio/HCD-RV2%20RV5%20RV6%20sm.pdf

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Click link and download manual:
https://servicemanuals.us/sony/audio/hcd-rv222da-hcd-rv333da-hcd-rv555da-mhc-rv222da-mhc-rv333da-mhc-rv555da.html

https://community.sony.co.uk/t5/home-cinema-projectors-players/how-to-repair-sony-hcd-zux10d-dvd-deck-receiver-always-display/td-p/2295791

You have a short, look to see if something is touching the ground portion of the unit.

Take it out of Demo mode then.

x402 replace

Before go, the standby/power LED will blink to a certain times, and these blinks are called blinking codes, and are fault indications. From the number of these blinks occur at one time switch ON, you can get an idea about the fault circuit stage inside the TV. If you wish to get more details about these blinking codes, check this link. if you're sound in electronics, you may get it repaired by yourself.http://electronicshelponline.blogspot.com/
Pull up previous posts by its left sidebar, or type in the brand name and model number to of your set, to its search box, and press 'Enter' or view it in Mosaic / Timeslide option.

i have a sony HCD-FL5D .it is not playing disc and not eject disc and when playing tape A/B it is on standby. i am worried about this please helpe me.

Your problem has nothing to do with the STK chip. The system on off is controlled by a microprocessor. The same chip controls the clock. You could be having a power supply problem. Check the 5V supply form the PSU board. Look into the STK only if you have a sound problem .

Led blinking Three times means B+ over voltage protection (OVP), unit goes to the standby mode then displays the 3 blink fault. This is also a problem in the power supply circuit, check T603 and R672. If you have electronic knowledge you may be able to fix it. Let me know if I could help you further.
Hope this helps.