Sony LCD with sound, no pic, ? scope findings

[tab_a]

Sony KDL40v-3000. Originally had no backlight, and 13 blink code. Found a bad CCFL and replaced that. Replaced inverter board and now had backlight.

I now have no blinking red light, just the green 'on' LED, audio, and no picture. Main board FB3, AU board, and t-con have all been replaced, though with used boards.

If I wiggle the t-con connector I see colored flashes on the screen.

I recently put an old TEK 465 on it and found that when I push the menu button, the signal on the t-con LVDS does change which I gather implies the main board is OK.

I'm trying to use the scope to figure out where the signal's being lost, but am moderately inexperienced. I'm concentrating on the AU board, in particular the CXA2240 audio/video chip--for which I can find no info.

With the scope I tested for signal at pins 104-106, labeled V1_c, _y and _V. Seems to be there. I then checked for signal at pin 90, labeled CV_out_2. Nothing. Then checked all labeled voltages on the chip: All good except pins 26, 27, 30, 31, 34, 35 which are all labeled 1.0v but all tested at 3v. Not sure if this is significant, or a misprint?

Will attach pic of boards and a screen shot of part of the chip schematic--hope it's legible.

Appreciate any advice as to whether I'm on the right track, and/or which way to proceed. Would also appreciate any suggestions about where to go to find info on what all those chip abbreviations mean. Many thanks!

[freakaftr8]

Re: Sony LCD with sound, no pic, ? scope findings

let's start with the basics are you getting 12 volts to the T CON board? If you say you have colored flashing on the screen I would only assume so. So next thing we have to find out if data from the t-con is physically being driven to the panel. I always start if I have no doubt is being driven to the panel with pulling one ribbon cable on one side of the t-con going to the panel it is seeing if I have half a screen you should see one side turn white and the other half either black or the picture being displayed. Then try the other side with the other side reconnected and see if the other side turns white that is a definite answer to you if you are getting voltage to the panel itself and if you get a display on one side but not connected all together usually that is in terpretation of a bad panel

[freakaftr8]

Re: Sony LCD with sound, no pic, ? scope findings

also you mentioned that all the boards have been replaced have they been replaced with the same revision number?

[tab_a]

Re: Sony LCD with sound, no pic, ? scope findings

Sorry I didn't mention those things. I had checked the t-con fuse voltage--12v both sides. I had also pulled the ribbon connectors individually (I've done a LOT of research on testing LCDs ) and there is no change. I've also checked the voltage regulators and they all seem ok.

Hadn't thought about board revision #s. The replacement FB3 board # is the same, and I don't see any revision numbers. OTOH, interestingly, though they look identical, the AU board # is different. The original--I think--is 1-873-856-11. The replacement is 1-873-856-12.

Early on, when I was sure it must be the tcon I put a replacement in that I later found out--via shopjimmy, I think--was only for the 46v-3000. I'll try to see if the above # differences make a difference.

Thank you!

[tab_a]

Re: Sony LCD with sound, no pic, ? scope findings

Shopjimmy seems to say the AU board I have in the set 1-873-856-12 works, but the -11 (which I THOUGHT was the original) does not. Other sites seem to think they both work.

[freakaftr8]

Re: Sony LCD with sound, no pic, ? scope findings

Swap tcon to the original part number and revision. Probably will fix your problem.

[tab_a]

Re: Sony LCD with sound, no pic, ? scope findings

I didn't state it clearly enough: Once I learned the t-cons weren't the same, I did get another that was the same as the original.

As mentioned, with the scope on a t-con LVDS pin, I do see activity when I push the menu button. Otherwise I see nothing, which leads me to believe the video signal is not getting to the t-con, so the t-con is unlikely to be the problem. Right?

Thanks.