KP-51WS510 blinking light but no picture at all. Audible click like usual followed by another click sound shortly after.

B+ current shrted. Repalce the D board you can get a replacement D board at www.tvrepairworld.com

High voltage problem, better left to a pro, expect to pay around $300-350 Julio [email protected]

6 blinks on your model means the +5V line is either overloaded or shorted on the A or B board. You can get replacement boards at the following link and they will assist you in determining which board of the two you actually may need.
http://servicemanuals.vstore.ca/

8 blinks is usually the error for a bad flyback. you can get a replacement at the following link and if your not sure which one your model uses click on the sony flybacks one at a time and it will tell which model they fit. Heres the link.
http://servicemanuals.vstore.ca/

I would suggest to turn the screen control potentiometer down a bit, this control is found on the front of your TV nearby the CRTs.
The part looks similar to the picture. Click here to see picture.
The red control is the one on the left if you are facing it.
Let me know if you need further assistance.

8 blinks in that model means High Voltage Error which means the flyback is defective and will need to be replaced. Sony parts list it as no longer available. But you can get it at the following link for 129.95 and it comes with free instalation instructions. the job takes about 45 minutes from start to finish. Heres the link.
http://servicemanuals.vstore.ca/

eight blinks means, "High-voltage error" and the probable cause location listed is, "T8005 is faulty (D board)". T8005 is the fly-back transformer assembly.

4 blinks is vertical protection circuit.

sounds to me to be a shorted HOT transistor or short somewhere. the click sound is the switch mode power suppy powering up sensing a short and quickly shuts down. the hot transitor is mounted to a heatsink near your flyback. check for emitter to collector short. you can try replacing it if shorted and if lucky that all that was ..but if shorts again you looking at probably a bad flyback. good luck

* Eight blinks - Problem with the audio (AUDIO), unit goes to standby and blinks the self-diagnosis code. Check IC406 audio amp, PS401, and 402. On some newer models of Sony TV sets, this code means that T8005 is defective on the D board. That would be the fly back transformer and the horizontal output transistor.