Sony KDL-40S5100

[Davegerg]

Re: Sony KDL-40S5100

Additional info: the green light is on steady. the white light coming through the holes in the chassis doesn't seem very bright. certainly visible but not extremely bright.

[Davegerg]

Re: Sony KDL-40S5100

I've got this exact model and getting the same voltages as shadetreetrader11. R6406 is 470 ohms. I jumped BL-ON with a resistor and backlight came on! The screen is still completely black and I can't see anything with a flashlight. I didn't try pulling out Q6704. Thanks in advance for any help.

[nomoresonys]

Re: Sony KDL-40S5100

Can you do a simple test? unplug cable from powerboard to mainboard, leave it off, plug power cord into powerboard, is there anything on the screen?

[Mrfix71]

Re: Sony KDL-40S5100

I have same model and symptoms. Power on I get green light and clicking of relay. No sound or backlight. Voltages on the PWR supply look correct. Should have jumped on buying the main board when I saw it last week!

I am going to print this thread out as it looks informative.

Keep up the awesome work

[budm]

Re: Sony KDL-40S5100

At this point since you are able to get the light source to work then if the main board is OK, beside of sending too low of the BL-ON signal, the T-CON and the panel are OK then you should have good sound and video, if not then you have more than just bad BL-ON signal.
If you study the service manual then you can see how the BL-ON signal is generated.

[shadetreetrader11]

Re: Sony KDL-40S5100

So do you think there's something on the main board that is dragging the 3.3v down?

[budm]

Re: Sony KDL-40S5100

Sounds like the multiple problem on the main board.

[shadetreetrader11]

Re: Sony KDL-40S5100

Installed the board on TV and again have 1.15v on bl_on. Ran a jumper from 3.3 stby and 680 ohm resistor in series to bl_on and the backlights came on. But when you look at the screen there's many vertical lines. Nothing changes if you connect coax to it.

[budm]

Re: Sony KDL-40S5100

I will not put that transistor in yet until you are able to get the Enable Voltage at the Enable pin of the IC.
So right now with all the board hook up all the Voltage at the pins you report in post 1 and 3 are still the same except the BL-ON pin 4 is now 0 instead?
That BL-ON Voltage is from the main board when TV is turned on, 1.15V is too low that is why I suggest you to use the resistor to simulate the BL-ON signal.

[shadetreetrader11]

Re: Sony KDL-40S5100

Those voltages were all taken with the board in the TV and the connectors hooked up. I wonder if for some reason that voltage reading was coming from something else. If you think that transistor will work I'll solder it in and put the board back in the TV and try it.

[budm]

Re: Sony KDL-40S5100

0 Bl_on: but you have a little over 1V before (#post 3) on that pin which is the receiving pit to receive the BL-ON signal form the main board.

[shadetreetrader11]

Re: Sony KDL-40S5100

I seemed to have damaged Q6704 while removing it. The SMD Code is LF I think it's a 2SC3052 SOT-23 package. I was looking at some of my junk boards I have laying around and I can't find one with the LF code. I found one with a SMD marking 16 I think that is a BC 847B. Wondering if that will work? both npn and the base,col,emit are in the same position.

[shadetreetrader11]

Re: Sony KDL-40S5100

With Q6704 removed there is 0 v on bl_on. R6406 is 470 ohms. So at this point I have both Q6704 and Q6400 removed.
CN 6154
2.08 Dimmer
0 Bl_on
1.59 Inv_err
gnd
0 Balancer_err

[nomoresonys]

Re: Sony KDL-40S5100

Did you try unplug cable from powersupply to mainboard? if backlights come on then try firmware update/reapply.

[budm]

Re: Sony KDL-40S5100

I went back to look at post #3 and realize that you only have 1.15V on the bl-on pin (CN6154 pin 4), I expect it to be for than 2.5V.
Please verify that R6406 (470 Ohms resistor is OK), it is connected between BL-ON (pin 4 of connector CN6154) which feeds the Enable pin of the IC.
You may want to try this, put 330 ~ 470 Ohms resistor between 3.3V power supply pin and the BL-ON pin of the connector after removing the BL-ON wire that goes back to the main board first to see if we can get the Enable signal to go high, right now it is either the R6406 has gone high resistance or the latch circuit is ON which you will have to remove Q6704 (Page 70 of the service manual) to find out, something is holding down that Enable line to 0V.

[shadetreetrader11]

Re: Sony KDL-40S5100

With Q6400 removed. 0v on "Backlight On Enable" located on connector CN6154. 0v on Pin 6 of IC. All three pads where Q6400 sits is 0v to ground.

[budm]

Re: Sony KDL-40S5100

Pin 6 of IC to gnd pin measures 11.65k ohms

So that does not look bad, I would try removing the Q6400 and see if the Voltage at the Collector (Backlights/BL-ON/ENABLE) will go up Or not when TV is ON. It has two protection circuits so we just have to narrow it down first to find out which one is keeping the Backlights/BL-ON/ENABLE low.

[shadetreetrader11]

Re: Sony KDL-40S5100

Pin 6 of IC to gnd pin measures 11.65k ohms

[budm]

Re: Sony KDL-40S5100

Emitter leg is at GND so it should be 0V.
Base is also at 0V, that means the MOSFET Q6406 is turned, so the Collector (Backlight/BL-ON, it is connected to the ENABLE pin of the IC through 0 Ohms resistor R6711) of Q6400 should be really high toward 5V.
There is another protection circuit (page 70) that can also stop the Backlight/BL-ON from going high if it detect bad lamp (LD - Lamp Detect); Q6704, 6705 from latch circuit driven by Q6706, Q6706 will turn on if the LD Voltage is less than 10V but you do have 12V on the LD pin so that is OK.
I need you to check the resistance between ENABLE pin and GND pin to see if it shows very low resistance (<100 Ohms) or not.

[shadetreetrader11]

Re: Sony KDL-40S5100


r6405 12v on vcc side and 0v on protection circuit side
r6407 0v on each side of resistor
r6417 3.4v on each side of resistor
0 volts on all 3 legs of Q6400