sony kdl-40w5500 no backlight or pic!

[attainteddragon]

hey guys, this one is beating me at the moment and a little help would be awesome.

lets start with some voltages. these are when powered on.

cn6150 ps to main supply

pin 1, power on, 3.358v
pin 2, ac off detect, 3.402v
pin 3, on/off, 3.397v
pin 4, unreg 15v, 15.16v
pin 5, unreg 15v, 15.16v
pin 6+7, unreg 15v ground
pin 8+9+10, reg 12v ground
pin 11, reg 12v, 11.95v
pin 12, reg 12v, 11.95v
pin 13, reg 12v, 11.95v

cn6151 ps to t-con

pin 1, reg 12v, 11.95v
pin 2, reg 12v, 11.95v
pin 3+4 reg 12v ground

cn6701 ps to inverter

pin 1, vcc 12v, 11.92v
pin 2, fb, 0.0v
pin 3, fb, 0.0v
pin 4+5 ground
pin 6, ld, 11.32v
pin 7, ld, 11.32v

cn6154 ps to main

pin 1, balencer err, 18mv
pin 2, ground
pin 3, inv err, 1.959v
pin 4, backlight on, 1.6mv
pin 5, dimmer, 2.3v

pfc voltage is good


after it trips the fault, it flashes 13 times once and then 14 times continually.

14 blink is meant to be t-con error, but the initial 13 indicates balancer error.

i have jumped the backlights on and they all seem good.

i have got to the point where i know that i am not getting inv on and that inv err is high from the time power is applied, so i am looking towards the main board.

just wondering if anyone else has any input on this one,

thanks.

[dick_barton]

Re: sony kdl-40w5500 no backlight or pic!

You have test points alongside the diode D101,102,103 etc. on the inverter board that you could test and see which point may be giving you the inverter error when you switch on. If your meter has min / max function it would help.

[attainteddragon]

Re: sony kdl-40w5500 no backlight or pic!

there is no activity on any of those test points. there is no backlight flash with all hooked up, as i get the feeling that the main won't let it come on, that is why the error is high and bl/on does not go high. just how i see it anyway.

btw, if i disconnect the error pin, it still reads high, so it has to be processed by the main i guess.

[dick_barton]

Re: sony kdl-40w5500 no backlight or pic!

The Sony manual posted has the schematic of the power supply IP1 in it.

It looks like IC6702 (page 46) is a comparator with one input (pin 11) connected to a resistor divider across VCC_12V and ground and the second input (pin 10) is from IC6700 (LX1692FIDW-TR) pins 18 & 19. The output of the comparator (pin 13) is the inv_err output.
The comparator looks as though it monitors the drive output Aout and Bout of IC6700

I suspect the fault is in the inverter circuit on the power supply board.

[budm]

Re: sony kdl-40w5500 no backlight or pic!

"i have jumped the backlights on and they all seem good." If you are able to force on the backlights, then do you see image on the screen? You should if all other functions of the main board are OK, if not then you have more than just bad BL-ON problem on the main board.

[attainteddragon]

Re: sony kdl-40w5500 no backlight or pic!

i put the ps on the bench and forced it on. the voltage on the cathode of the dual diode that comes from the comparator circuit reads around 100mv on both of those diodes. the 1.9v on the inverter error pin is NOT present. hooked it back up to the main and the same voltage is still on the diodes, but the 1.9v inverter error pin is now present again.

bud, the main was fully isolated from the ps when forcing the ps on, so no picture on screen.

[budm]

Re: sony kdl-40w5500 no backlight or pic!

I would hook everything back up, then remove the BL-ON wire going back to the main board and then use 1K between the BL-ON pin of the power supply and the STBY Voltage to force on the backlights to see if you will get the image on the screen when you turn on the TV, if not you have more than just bad BL-ON signal.

[attainteddragon]

Re: sony kdl-40w5500 no backlight or pic!

tried jumping the backlights with the main hooked up and it didn't give me pic. also tried grounding the error voltage to see if that helps, and still no go. error voltage is high from the time power is applied.

i know that i have main issues due to no bl/on signal. so i will see if i can find one. i may of stripped one of these in the past, but need to sort and catalogue my stock. could take a while. :O

[budm]

Re: sony kdl-40w5500 no backlight or pic!

If you get the light source to come on, if the main board and T-CON boards are good then you should have pictures and sound, at this point it looks like you have main board problem, you can also check to see if you get 12V at SMD fuse on the T-CON, if the main board is good then it should also send the 12V to run the T-CON.

[attainteddragon]

Re: sony kdl-40w5500 no backlight or pic!

12v is present at t-con. fuse is good. not sure if this error voltage does anything else while on the main. found that it generates from the 12v on cn6150. with those pins disconnected, i don't get the error voltage, but lose functionality of the set at the same time.