Sony KDL-37XBR6 Black Screen :(

[dick_barton]

Re: Sony KDL-37XBR6 Black Screen

Connect everything back together and test the voltages again as in post #19

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

Connect everything back together and test the voltages again as in post #19

Hi dick_barton,

Can you tell me where I am supposed to connect the probes from my DMM? I'm not really seeing how I can do this once that connector is plugged back in place on the power supply board. Sorry for being newbish here..lol

[dick_barton]

Re: Sony KDL-37XBR6 Black Screen

You can push a thin piece of wire alongside the grey wire going into the connector or tape a pin to your meter probe and push alongside the wire going into the connector. Black lead on chassis, meter set to volts DC.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

You can push a thin piece of wire alongside the grey wire going into the connector or tape a pin to your meter probe and push alongside the wire going into the connector. Black lead on chassis, meter set to volts DC.

OK, Thanks! I will report back later with the measurements! BTW, Do you think that being a 2008 model TV is worth to try and fix? Just saying because what if it is the power supply and that corrects the problem, but a few weeks/months down the road something else goes out.

Another thing is that the main video board is very hard to find from what I see as far as searching for it. I have also been told that I would have to install or update using a memory stick/flash drive?

Thanks again!

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

OK, I have the measurements with the power cord just plugged into AC without the Power button pressed:

Pin#1,2,&3=REG12V/ all pins measured 12.04V
Pins#4,5,6=SGND (not measured, grounds)
Pins#7 and 8=SGND1 (not measured, grounds)
Pin#9 & 10=UNREG 13V/ both pins measured 16.16V
Pin#11=STBY 3.3V/ pin measured 3.37V
Pin#12=AC_OFF_DET/ pin measured 3.08V
Pin#13=Power ON/ pin measured 3.29V


After pushing the Power button on, here are the voltages:

Pin#1,2,&3=REG12V/ all pins measured 12.26V
Pins#4,5,6=SGND (not measured, grounds)
Pins#7 and 8=SGND1 (not measured, grounds)
Pin#9 & 10=UNREG 13V/ both pins measured 16.55V
Pin#11=STBY 3.3V/ pin measured 3.36V
Pin#12=AC_OFF_DET/ pin measured 3.07V
Pin#13=Power ON/ pin measured 3.27V

[dick_barton]

Re: Sony KDL-37XBR6 Black Screen

"Power On" normally changes state when you come out of standby so it looks as though the mainboard is holding the power supply in the "On" state.

Can you also post as above for connector CN601

Can you also check what voltage you have on the fuses on the inverter board

[budm]

Re: Sony KDL-37XBR6 Black Screen

I suspect the black fuse with '20' printed on top.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

"Power On" normally changes state when you come out of standby so it looks as though the mainboard is holding the power supply in the "On" state.

Can you also post as above for connector CN601

Can you also check what voltage you have on the fuses on the inverter board

OK, I checked the 3 fuses, and they all checked good. Then I measured the voltages. For the fuse with the "20" on it, it measured 24.23V, and when I pressed the Power button on, it dropped a little to 23.74V

Then I measured the (2) other fuses marked F101 & F301. They both measured the same at 24.22V, then 23.74V with Power button pressed on.

Here are the measurements for CN601 connector:

Pin 1-5 are all the same voltages reading 24.22, then 23.79V when power on. The rest of the pins are SGND.

[budwich]

Re: Sony KDL-37XBR6 Black Screen

Since you have 12v produced at the power board and nothing at the tcon (fuse test shows 0... if correct), then you need to trace the wiring from the power board over to the main board as it is likely that the main board switches that power towards the connector that shows up on the tcon... hopefully you follow that. You can maybe follow the wiring on the cabling ... probably difficult since they appear to be similar in color / markings. Use you meter on continuity and go from one end of the cable to the other to find out where the wiring leads on the main board.

Having said that, can you recheck the fuse on the tcon (3a)... but do this with continuity... use a ground point for one probe and then test each side of the fuse. It is possible that fuse is attached to a ground as opposed to a "supply". Then do the continuity across the fuse itself.

[budm]

Re: Sony KDL-37XBR6 Black Screen

Right now I am a little confused, do you have backlights or not? oN POST 1 you indicated that you can see the channel number on the screen but the screen is black.
"Also, if I press on the front screen, I can see a small white light. It also appears to be stuck on one channel as I can't lower or raise both the channel buttons or the volume button."
It is not making any sense on the data we are getting if the there is no Voltage on the T-CON then you cannot have any image on the screen.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

Since you have 12v produced at the power board and nothing at the tcon (fuse test shows 0... if correct), then you need to trace the wiring from the power board over to the main board as it is likely that the main board switches that power towards the connector that shows up on the tcon... hopefully you follow that. You can maybe follow the wiring on the cabling ... probably difficult since they appear to be similar in color / markings. Use you meter on continuity and go from one end of the cable to the other to find out where the wiring leads on the main board.

Having said that, can you recheck the fuse on the tcon (3a)... but do this with continuity... use a ground point for one probe and then test each side of the fuse. It is possible that fuse is attached to a ground as opposed to a "supply". Then do the continuity across the fuse itself.

I connected the ground wire of my DMM to ground on TV, then checked each side of the (3a) fuse. No continuity on either side. Also, fuse showed good.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

Right now I am a little confused, do you have backlights or not? oN POST 1 you indicated that you can see the channel number on the screen but the screen is black.
"Also, if I press on the front screen, I can see a small white light. It also appears to be stuck on one channel as I can't lower or raise both the channel buttons or the volume button."
It is not making any sense on the data we are getting if the there is no Voltage on the T-CON then you cannot have any image on the screen.

As I stated in post #1, I do see lights on the back that light up when I turn the power on. I assume that is the backlights. The screen is black, but if I press on it, I can see light where my finger presses in on the front screen. The panel on the very top of TV is what I was talking about being stuck on one channel. There is no channel number displayed on the front screen. I get absolutely nothing but black on front screen!

[budwich]

Re: Sony KDL-37XBR6 Black Screen

I connected the ground wire of my DMM to ground on TV, then checked each side of the (3a) fuse. No continuity on either side. Also, fuse showed good.

OK.... So, if this is all true, then whatever that fuse is protecting is getting nothing in terms of voltage... and if what was posted earlier, it should be 12v, AND 12v is at the connector leaving the power board... then where ever it is going, ultimately it isn't getting to the tcon. As suggested, you need to track that 12v from the power board to the main.

[budm]

Re: Sony KDL-37XBR6 Black Screen

So to be sure, you are 100% sure that you do not have 12VDC (with ref. to the chassis GND when TV is turned on) at either end of the whire SMD fuse (with '3A' printed on top, correct?

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

OK.... So, if this is all true, then whatever that fuse is protecting is getting nothing in terms of voltage... and if what was posted earlier, it should be 12v, AND 12v is at the connector leaving the power board... then where ever it is going, ultimately it isn't getting to the tcon. As suggested, you need to track that 12v from the power board to the main.

I did check the other side of the connector cable coming from the power supply board to the main video board. It is showing that the voltages are getting there. I also checked the cable that comes from the main board to the t-con board. The voltages are all about the same being around 1.3V.

I believe that should be higher? Also checked that (3A fuse on t-con, and no voltage at all. I believe it must be the main video board. I see that it must have some transistors or an IC that requires a heat sink?

I'm wondering if perhaps these main video boards have an issue with the components that are heat sinked?

I have looked around on Google trying to locate a main board, but looks like a hard to get item. Any suggestions on what I should do at this point?

Thanks again!

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

So to be sure, you are 100% sure that you do not have 12VDC (with ref. to the chassis GND when TV is turned on) at either end of the whire SMD fuse (with '3A' printed on top, correct?

Yes, there is no voltage at that fuse on either side of the smd fuse (3A)

It appears, and only an assumption, that the main video board must be bad.

I'm guessing that the components that have that heat sink may be the issue, but not sure.

Thanks for your help!

[budm]

Re: Sony KDL-37XBR6 Black Screen

At this point you will have to locate the switched power MOSFET that supply the 12V to the T-CON board, it should be closed to the LVDS connector on the main board, it may also have the fuse (micro fuse) for that 12V circuit also, have to look at the diagram of the main board to find out for sure.
I hope you know how to read schematic and have ability to do SMD repair works.

See attached PDF for the info I provide.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

I do have some hands on with soldering, but I know that these smd parts are very difficult due to the small sizes. I can read schematics for the most part.

So basically I have a choice of either trying to change these transistors, maybe that fuse you mention, or if I run across another main video board, I can just replace this one, and it should work again?

[budm]

Re: Sony KDL-37XBR6 Black Screen

First you have to locate the switched MOSFET then check to see if it has 12Vdc feeding it or not then check to see if it has command signal from the processor to turn it on so it will pass the 12VDC to the T-CON board, you also need to verify if there are any fuses on the main board, if there are then you need to test them for continuity and Voltages. It is just step by step you have to go through to troubleshoot the problem down to component level.
Or try changing the main board, if I were you I will try locating the components above first.

[Gammaray]

Re: Sony KDL-37XBR6 Black Screen

Thanks! I will try and do like you say. I guess I will have to remove the heat sink to get to the MOSFET? I'll also look for any fuses on the board and check for continuity and voltage. I'll report back here later once I get the chance to do this.

Big appreciation to all here who have tried to help me with this! Wishing you all the best! Cheers!