Sony Bravia KDL-46VE5 Repair Help/Service Manual Power-On Click

[edy_b]

Hi folks,

I'm trouble-shooting a Sony KDL-46VE5 found curb-side. Plugged in, standby light on, green light power on all OK and it would click on... Then after a few seconds it would turn off. Standby light blinks 6 times... Error table indicates it could be a whole lot of stuff.

So I opened it up, went to test some voltages and unplugged the cable (9-pin) that goes from Power supply to the Inverter/Balancer board. The cable is labelled with pins:

HEATER-ON
FB
GND
GND
GND
Protect
VCC-12V
VCC-12V
VCC-12V

Well, after I unplugged this cable, the TV powered on! Screen ok, backlight ok, signal ok. I was able to play video, sound all good. TV works a charm.... yet only while this 9-pin cable is UNPLUGGED!???

So what do I do now? Do I leave it unplugged and use the TV that way? I haven't been able to find the schematic for the inverter/balancer board and figure out what the purpose of this cable is, and why it being unplugged fixes the problem.

Any help would be appreciated.

[Nick's Tvs]

Re: Sony Bravia KDL-46VE5 Repair Help/Service Manual Power-On Click

My guess is that you have a bad CCFL tube in the set and by disconnecting the cable, you are eliminating the protection circuit. You are also eliminating your ability to control the brightness as well most likely as well as a few other backlight options.

[edy_b]

Re: Sony Bravia KDL-46VE5 Repair Help/Service Manual Power-On Click

Thank you, I did confirm that I can adjust the backlight through the menu and I can see a difference. Perhaps there would be more "variation" of brightness in a normal set? I can also see a difference when I cycle through VIVID, STANDARD, CINEMA, CUSTOM modes in picture. If there is a bad CCFL tube in the set, I am also not noticing it through the screen.... It is perfectly watchable. Then again, I do not have a brand new working set to compare it to, so maybe a working one would have a greater range of brightness possible? As far as I am concerned though, it seems to work just fine and has an excellent picture and sound, and powers up quickly. If somebody gave me this TV and did not tell me anything about it, I would think it is a normal set.

Someone on another forum suggested that the PROTECT line may be normally HIGH and that this causes a transistor on the board Q6714 to be off which tells the MCU that everything is working. If I have a fault on the Balancer Board and the PROTECT line becomes LOW, it would make Q6714 high and notify the MCU that there is an issue. But if I disconnect the cable, it may return Q6714 back to an off state which signals the MCU that there is no fault, allowing the TV to turn on. Basically, disconnecting the cable defeats some kind of error signalling and therefore tricks the MCU into allowing the TV to turn on.

If this is the TV just warning me about a bad CCFL and it is not doing anything else, then I may just leave it alone. If it is a bad CCFL it will be a pain to try and fix it. If all the CCFL's are good and it is an electrical fault then again I will have to trace through all the components to see where the fault lies and reconnect the cable once fixed. However I am not confident in my electrical trouble-shooting abilities to go through the many components and test each one, and replace them (many of which are SMD's). So I may leave things "as is" for now.

I was hoping the fault was a more simple, like a few leaking/bulging capacitors and then I could just replace them... like I have typically found in other TV's, monitors and computer PSU's I've worked on. I am thinking this repair may be above my experience but I got lucky pulling that cable to test the PS output on the pins and noticed the set turned on. If I start desoldering components I have a feeling I will kill the set.

[vicvc]

Re: Sony Bravia KDL-46VE5 Repair Help/Service Manual Power-On Click

quite a few posts relate to checking back lights with power saver (neon). it will help you to get a better understanding of how to go about testing and improve your knowledge. running a set without protection can result in a burnt down house. one or more of the inverter transformers are most likely busy burning and that will cause the protection to operate.

[cyberhack]

Re: Sony Bravia KDL-46VE5 Repair Help/Service Manual Power-On Click

Also from the photo there looks like a bad cap

[edy_b]

Re: Sony Bravia KDL-46VE5 Repair Help/Service Manual Power-On Click

Thanks for the suggestions. I have the schematics/service manual now if anyone needs. @cyberhack can you tell me which cap you think is bad? I didn't see anything bulging/leaking, and I will have to desolder them to check as I only have an out-of-circuit ESR tester.

I also don't want a fire hazard, and I believe the problem is likely on the IP3N main power board because otherwise the display functions perfectly with no evidence of any backlight issues. Brightness is smooth and even across the display, I can change various modes (Vivid, Standard, Cinema, etc) and TV works completely fine otherwise. I would expect if it was an inverter board issue or bad CCFL it would still put out 12V on that 9-pin connector which it doesn't. So there is at least definitely an issue on IP3N, and maybe perhaps somewhere else but until I can solve the IP3N board problem I cannot be sure.

Therefore, with everything unplugged on the IP3N board except power I will check to see if there is proper voltages on the 9-pin connector going to the inverter board (with pins HEATER-ON, FB, GND, GND, GND, PROTECT, 12V, 12V, 12V).... If that is not putting out 12V then it may be not powering some circuit on the Inverter board properly that checks for faults/self-diagnosis, which in turn sends back an erroneous PROTECT signal to IP3N to indicate an error and power down. With the cable unplugged it must default the power supply to stay on rather than shut off... maybe it needs a HIGH to signal an error, and LOW means all ok?

[alizona]

I have the schematics/service manual now if anyone needs.

I have the same rescue TV. On mine the R6016 inrush resistor will blow. If I manually trip the relay and hit power it works fine.
All the components I can test are good and I have spent hours probing the primary for a short to no avail.
Anyway, I'd like to take you up on your offer for the service manual and anything else you've come across since that you think might be helpful. Thanks.