Sony KDL-52XBR4, manf date July 2007
Originally this was going to be a help thread, but I found what I needed through searching this forum and was able to mostly fix the TV, so I'm going to pay it back and post a summary so that future people with the same issue can find the solution quicker!
Symptoms:
TV powers on with green power light. Right after power up the backlight will flash briefly and then typically stay off. If you leave the set on for a long time, once in a while it would flicker on for 10 minutes and work 100% perfect. There were NO blink code error messages (until I started disconnecting things).
I tried a different DF4 board, no change. I tried a different left upper and lower inverter board (rev 0.0 vs my rev 0.4), no change. I tried a different right upper and lower inverter board (0.0 and 0.5 compared to my rev 0.4), no change.
if I unplugged cn6701 then the backlight would stay on for ~1s (looking fairly even) and then the unit shuts down with a 6 flash sequence. So I thought the inverters were probably OK.
At this point I was thinking it was one of the florescent tubes due to the age of the TV, even though there were no balancer or inverter errors. I had tried searching online on how to figure out which tube is the problematic one but all of my ohm tests and voltage tests did not identified an outlier.
Resolution:
I had tried the above in my free time over the course of a couple months. Finally the other day the wife was sick of it in pieces in our basement and I took another hard look at it. I then found someone on badcaps having a similar issue with an entirely different brand of TV because of the DIMMER signal. I don't recall which thread anymore unfortunately. And then I found the service manual here ( dkneyle - https://www.badcaps.net/forum/showthread.php?t=35607 ). From this I was able to monitor INV_ERR, BALANCER_ERR, and DIMMER (among other things). Everything but DIMMER seemed to check out. DIMMER was consistently very low (cant remember exactly, maybe .01VDC) when it should have been 1.4-3.0VDC.
I pulled the DIMMER pin from the connector at CN6706 on the DF4 board and powered up the tv and BAM, the backlight stayed on and everything looked good and the TV is working great with the exception of backlight brightness adjustment. I'm not sure where in the range it is by default (the pin on the inverter measures about 2VDC but I don't know if that is meaningful since the signal comes from the microcontroller normally) but for a living room TV the brightness seems to be OK.
Anyone that has any thoughts on troubleshooting the DIMMER being 0VDC fire away. It would be cool if the unit was fully functioning, although I can't complain as it is very usable right now.
Originally this was going to be a help thread, but I found what I needed through searching this forum and was able to mostly fix the TV, so I'm going to pay it back and post a summary so that future people with the same issue can find the solution quicker!
Symptoms:
TV powers on with green power light. Right after power up the backlight will flash briefly and then typically stay off. If you leave the set on for a long time, once in a while it would flicker on for 10 minutes and work 100% perfect. There were NO blink code error messages (until I started disconnecting things).
I tried a different DF4 board, no change. I tried a different left upper and lower inverter board (rev 0.0 vs my rev 0.4), no change. I tried a different right upper and lower inverter board (0.0 and 0.5 compared to my rev 0.4), no change.
if I unplugged cn6701 then the backlight would stay on for ~1s (looking fairly even) and then the unit shuts down with a 6 flash sequence. So I thought the inverters were probably OK.
At this point I was thinking it was one of the florescent tubes due to the age of the TV, even though there were no balancer or inverter errors. I had tried searching online on how to figure out which tube is the problematic one but all of my ohm tests and voltage tests did not identified an outlier.
Resolution:
I had tried the above in my free time over the course of a couple months. Finally the other day the wife was sick of it in pieces in our basement and I took another hard look at it. I then found someone on badcaps having a similar issue with an entirely different brand of TV because of the DIMMER signal. I don't recall which thread anymore unfortunately. And then I found the service manual here ( dkneyle - https://www.badcaps.net/forum/showthread.php?t=35607 ). From this I was able to monitor INV_ERR, BALANCER_ERR, and DIMMER (among other things). Everything but DIMMER seemed to check out. DIMMER was consistently very low (cant remember exactly, maybe .01VDC) when it should have been 1.4-3.0VDC.
I pulled the DIMMER pin from the connector at CN6706 on the DF4 board and powered up the tv and BAM, the backlight stayed on and everything looked good and the TV is working great with the exception of backlight brightness adjustment. I'm not sure where in the range it is by default (the pin on the inverter measures about 2VDC but I don't know if that is meaningful since the signal comes from the microcontroller normally) but for a living room TV the brightness seems to be OK.
Anyone that has any thoughts on troubleshooting the DIMMER being 0VDC fire away. It would be cool if the unit was fully functioning, although I can't complain as it is very usable right now.
