Check BL_ERR pin on back light inverter board, what is volt reading that you get before and after tv shuts down? Let me know to proceed.
Thanks.
BTW, I really enjoyed your quote * I don't trust the blinking anymore *
.
OK, BL_ERR should remain close to 0V because it is Balancer Error signal that shuts off tv. Balancer error shows bad back light inverter board and/or main board problem.
Are you sure you got good/ working back light inverter board as replacement?
You know there is no schematics for inverter or main board of LCD TVs and board swapping is the only option to rectify the problem.
Reason of 2 times blinking would be due to misaligned connectors on power board or on inverter board while replacement. Only 24V goes to inverter board and its still available that means inverter board is working.
If you can disconnect BL_ERR output temporarily going to main board that may help you to narrow down the problem, if main board gets 0V as BL_ERR then back light should remain On.
Its OK, now ground BL_ERR pin on main board to check is it generating error signal itself?
OK, that means BL_ON goes low/ off at inverter board and that command comes from main board, check is that happening?
I'm going to bed now and wont be online for next 8-10 hours so do not reply this post OR site has 4 hours timer and we will lose contact and your question will go to open question area for other experts.
Hey, I'm up and running again.
I'm working at Fixya since last 3 plus years so I get all your messages/ posts/ comments, no problem at all, you know I know my ways.
Regarding BL_ON command, its present all the time and back light still turns Off that shows inverter board is not good.
There are just few connections in connector to do the job, Dimmer, BL_ON, 24V, GND and BL-ERR in case of problem.
BL_ERR is cut off so main board is not getting any error signal, BL_ON is on all the time, 24V is available all the time, GND is connected, what else is left now? ... Inverter Board !
Swap it in another similar model, if its possible to verify it.
Yes, Dimmer is also command to control light intensity of inverter board, can you provide it 3.2 volts externally?
I hope you will use 1K resistor to apply 3.2V at dimmer pin.
Yes, and I would suggest to use 1K or similar resistor to avoid any current drain in dimmer circuit.
Good to know that you got picture in tv.
We just fooled the protection system in tv to turn On the back light to get picture in lcd panel. There are two boards that should be swapped in working tv to find out which one is bad.
Usually I have this option in my repair shop or get it arrange to swap the board then I order replacement board.
If its your personal tv then you may keep using it with same arrangements as its not harmful.
oops, forgot to mention those two boards, back light inverter board and main board.
Thank you so much, you did great job indeed.
Have nice time.
I'm from Pakistan and hopefully will be available for any help in electronics stuff.
×
These service may be close to your chassis:
http://elektrotanya.com/?q=showresult&megnev=sony&megnev2=KDL-40ex&kategoria=&kat2=all
Since the backlights inverter board is also used in the EX400/403/500/701:
http://www.shopjimmy.com/samsung-lj97-02541a-backlight-inverter.htm
Then you can download the manuals for the EX500 to see if it will close enough to troubleshoot the problem. I myself do not go by the blinking lights any more, it is only as good as the person that write the software/firmware to detect the faults that can be caused by more than one component failure.
Please post back what you find, I will have to download the manuals and see what it can be also.
Basic LCD monitor and TV troubleshooting guide:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r7406380-tv_training_manuals
Failed TV and Monitors pictures: http://s807.photobucket.com/albums/yy352/budm
Learn about bad caps: http://en.wikipedia.org/wiki/Capacitor_plague
Parts: www.shopjimmy.com
Parts: www.interliquidparts.com
Capacitors kit: http://lcdalternatives.auctivacommerce.com/Default.aspx he can make you a set of caps.
Or www.digikey.com, just make sure to use caps with low ESR, 105c, high ripple current and long life rating such as PANASONIC FM or FC series.
1,473 views
Usually answered in minutes!
Hi, thanks for responding. Yeah, I should of known it wouldn't give me such a simple solution.
I checked the voltage on BL_ERR and it reads 3.27v in standby. When the set is powered on, it goes to 0 whenever the screen turns on and then returns to 3.27 in between those three times and when it's in standby again.
Hmm...I thought I did. I got it off Ebay, described as pulled from a working unit and guaranteed not DOA. Maybe something else I shouldn't of trusted.
Is it possible something else is damaging the inverter boards, because I did get 2 blinks repeating the first time I plugged the set in after I replaced the inverter. After I powered the set on, I never got the 2 blinks again. Is there a way to test whether the inverter board is good? You also say it's possible the BL_ERR reading could mean a problem with the main board. Is there something I can do to check that?
Okay, I'm willing to replace the main board too if that's where the problem is. I cut the BL_ERR lead going from the power supply to the main board (no problem to solder it back later with shrink tube), but I also cut the BL_ERR wire to the inverter by accident. Hope that doesn't mess up the test. The thing is, the line to the main board seems to be an input. Before I cut it, it read 3.27v at the main board terminal. After the cut it still reads that on the main board and 0 at the power supply. Is that the way it's suppose to be? Anyway, the screen does the same thing: lights up with logo and tone three times and then back to standby.
Alright, we're getting closer. When plugged in now I get the audio of the channel but not the picture. Actually, the picture does seem to be there. It's difficult to tell but when I hold a flashlight up to the screen I can barely see the picture. So its just that the backlight isn't staying lit after it turns on for a few seconds to show the Sony logo.
Oops, still learning how this site works. I didn't see the rest of your last message and sent a reply. If you didn't get it this is what I wrote:
Alright, we're getting closer. When plugged in now I get the audio of the channel but not the picture. Actually, the picture does seem to be there. It's difficult to tell but when I hold a flashlight up to the screen I can barely see the picture. So its just that the backlight isn't staying lit after it turns on for a few seconds to show the Sony logo.
Also forgot to add that standby isn't blinking anymore. Want you to know I really appreciate your help with this. I realize my measly 15 bucks doesn't really cover the knowledge and experience you guys give generously.
Oops, again. Thought your last message was the one before. Give me a sec to check BL_ON at the main board.
It's very strange. Voltage reads 3.25 for BL_ON at both the main board and inverter board and yet the backlight doesn't stay on.
The current inverter board is a replacement that's suppose to be good, so I swapped the original board back in and the voltages are the same and the tv does the same thing: turns on and I can hear audio but the picture becomes black after the Sony logo and tone. I wondered if it might be dimmed all the way and checked the dimmer voltage. It's 3.2v when the set is first turned on then drops to about 2.2 when the screen comes on with the logo and then drops to 1.6 when the screen goes black. Does that mean anything?
Could I use the 3.3v standby voltage pin on the power board?
Alright! Guess that was it because I've got the picture now too. Closest resistor I had handy was 2.2k and first used the 3.3v standby pin but I forgot to cut the lead to the dimmer and it didn't work. So I used 3 volts from a universal power supply with the 2.2k and of course still didn't work until I realized the lead from power supply needed to be cut. So the standby voltage probably would work. So would a solution be to run the set jury-rigged like this or do we know which board needs to be replaced?
Great, thank you. I went from thinking the tv might be a lost cause to having a working set and knowing the right possibilities for a more complete repair. I'm very satisfied and will be accepting this solution. Thanks again.
I'm very happy with this solution. The tv is working now and I don't even have to replace any boards if I don't want to. I highly recommend this site and the expert who helped me, welcomejee. He zeroed in on the solution from the start and answered all my questions. It was a pleasure working with him.
I hope I'm still able to thank you for responding. I've accepted another solution but I appreciate your time and the information.
×