Bigscreen rework

Video Asylum

TVs, VCRs, DVD players, Home Theater systems and more.

Last week my big screen TV started acting up. It's a Sony 46 inch that I've had for a few years. How when I bought the thing new I could see that the turner was noisy, so I went in and filtered the five voltages going into the tuner and lowered the noise by a lot. This new problem had to do with false color over 2/3 of the screen. I had shadows of blue and yellow. The center of the screen was normal. This would come and go at first, but was getting worse. I took the back off the unit and poked around with a wooden stick to see if I could find anywhere that it would make it act up. No go there, so I removed the front speaker grill. Under this there is a cover that protects the PCB that has all of the sets convergence controls. That's about 50 pots! Poking again with my stick I made the color go bad for good. OK, now I knew where the problem was. I removed the wiring harness that has eight plugs on it. All are different from one another so I couldn't ness up where they go. Next, four screws to remover the PCB and it's heatsink. The heatsink is for two very large IC's that have 30 pins each going into the PCB. Five screws removed the PCB from the heatsink. Turning the PCB over I found five or six broken solder joints! I re-soldered everything on those two IC's and put everything back together. It worked! In fact it looked better than it had for some time since it must have been going bad for a long time. Now thinking about that PCB I could see there were voltages of 18 volts, 15 volts and 5 volts, both plus and minus. The filtering was poor with most only have a few 22uF caps. As I do with everything I own I replaced all those caps with larger values of 2200uF, and 1000uF. I changed out about a dozen caps to start with. The picture looks GREAT! The noise dropped by a lot and so did the graininess. It almost looks like HDTV! Where you can really tell is text, any text on the screen is now very sharply focused. When I did a convergence, the cross was now steady, not shaking like it used to. The channel numbers used to be kind of fuzzy but are now clear and sharp. The next step will be to change out some of the op-amps they used with better newer units (seven in all). The set has 4558's in it and I'll be trying AD712's and AD827's to see if they help any. On these op-amps they used 100ohm resistors into the power pins but NO by-passing! On four of these op-amps I added caps and sockets, the effect was small but still worth it. All of this is again just one to one swap, so it was real easy to do. Don't be afraid to get into your own unit and make it better too. I dare say that if TV's were done right, there would be a lot less hub-bub about HDTV. Good Luck, bobwire

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The Cable Cooker

Topic - Bigscreen rework - bobwire 13:43:34 08/21/02 (4)

Re: Bigscreen rework - Estes 05:19:22 08/22/02 (3)

Re: Bigscreen rework - bobwire 07:44:03 08/22/02 (2)

re: JVC 36" direct view... - Estes 09:10:33 08/29/02 (1)

Re: re: JVC 36" direct view... - bobwire 17:33:39 08/31/02 (0)

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