I am wondering what steps I should go through to resolve what appears to be an intermitent power problem in a Sony KP-51HW40 (2002) rear projection television. Symptoms are that: immediately after the set is turned on a clear, convergence adjusted, color picture appears with clear sound, but narrow vertical columns of black and white hyphen length lines about 2 inches apart, rotate from left to right across the screen at a moderate pace. At the same time the red, green and blue color guns flash sporadically every 5 or ten seconds, and fade slightly in intensity on the same basis, alone or in concert. After about five minutes of this the TV turns off, but can be restarted immediately, displaying the same pattern all over again until it once again turns off. Banging the side of the TV while in the on mode, induces the flashing symptoms at each strike. The inside of the TV is relatively clear of dust or dirt. What can be diconnected and then reconnected internally in an effort to narrow the search for a bad connection. Ken Soehn
Ok, your problem is probably triggering the AKB circuit, this is a circuit, that checks the current flow through the cathode of the crt, to make sure all three tubes are working correctly, if one tube is acting up the other two will loose video, until the tube acting up is working again. Several things could be wrong, I will start with the easiest, First try to remove the crt boards and clean the pins on the crt's use a emery board and lightly sand the pins a little and clean the sockets with alcohol or some kind of circuit board cleaner. If that doesn't work try tapping on the focus block, this is a control with 6 control knobs on it, it is located in the front of the tv under the front service panel, you take of the gray (if it is gray not sure on yours) panel covering the front of the tv, under that is a fiber board panel, remove the screws and the control will be exposed, you can also get to the crt boards from here. If none of this works take the butt of your screwdriver and tap on "D" board and see if you can get it to act up if so you have a bad connection somewhere on "D" board. If none of this helps, you could have a bad crt sonys around this model are known to have picture tube problems.