This problem is common with this type of reciver. I actualy was searching for a new idea as how to fix mine... PERMENENTLY!!!!!!!!!!!! No such luck. But here is how mine went this time. The large caps on the main board have been realy overworked, wore out, shorted out, then blew. This then kept the power ic and it's less than adequate parts from getting enough power. This caused them to go BOOM! I think the stk4221 might still be good... but I don't know for sure this time. Diong a google search on this ic I found the stk4221v is made by Sanyo! If your feeling ambitious look for the data sheet and build the circuit in it (exemple) with real parts. Also replacing those large caps on the main board with bigger ones may help (havent tried that yet though). I hope some of this may be of help to you. It's the same thing with an old Pioneer reciver of mine. It blew and I started replacing crar with better parts. If the do the same thing and fit use them. But at your own risk. One mad Sony (guts by Sanyo) owner to another, Jason

Damn, its been a while since someone replied to this. Basically I was sarting to remove each component off the ic board one at a time until I found the one that triggered the overload. The caps your refering to were going to be the next ones being removed..lol. I just have not had the time to mess with the stereo lately, to much goin on around the homefront. Thanks for yor reply, im going to try that next....

I have the same problem with my STR-AV53. They seem to have the same parts in them. Anyway the power ic board has a tendency to blow the capatisitors (spelling?). The real hard ones to check are the real small resistor looking ones (they don't have the dimple in the middle). I have rebuilt mine once already... and going in for the second time. I'm not sure yet if the main power caps have something to do with it... but you never know. Good luck.

Well the IC did not fix it... Im now working on the board to find out where the problem is. The stereo powers up fine if this is disconectted, but as soon as I plug it in it goes to crap...

Ok, here is what I found... The part number IS #163858811..the problem is thats the part number for the power ic board that is discontinued and I cant find anyone that has one in stock. The problem now is there is a 3" wide black colored part soddered to the board that is marked stereo amplifier w/ a #STK4221V as a number. This part mounts directly to the massive heat sink inside the stereo. Im guessing this is the part I need and not the circuit board it is mounted to. My next question is, is there any aftermarket replacement for this part and can I soder the old one off and the new one on?

Here is all the numbers on this component... Its called Power IC #1-638-588-11 The black thing hanging off of the circuit board is marked.... Stereo Amplifier STK4221V is stamped on the front, and on the rear its marked: E4221BDA9... On the botom of the circuit board its marked Power. IC CMKS-81X

Would you know how I can contact them for the part?

This Part 1-638-588-11 is a Supply end part by Sony Regards Sivaram