Sony KDL55EX720 won't turn on

[tibimakai]

Re: Sony KDL55EX720 won't turn on

That one it was a 46EX400.
You are suspecting a mainboard also?
I will try to power the T-Con too and see what will happen.
I would like to be sure, that the panel is OK, before I would purchase a mainboard.
I was told, that the TV has a 5 blink error code and actually it was completely dead, something sounds fishy here. Maybe the TV technician did something to it before he returned the TV? The switch/IR sensor/LED board was disconnected from the mainboard when I opened the TV. I'm wondering why?

[budm]

Re: Sony KDL55EX720 won't turn on

If someone worked on it before you, then you really have to look real close at everything to make sure all the wires and connectors are back in place, no bad solder joints/bridge, etc. Something was done that caused it to be dead instead of seeing the original symptom of 5x error code.

[tibimakai]

Re: Sony KDL55EX720 won't turn on

The owner of the TV, took it at a repair shop, most likely to evaluate the problem, I don't think they really did much to it. They said, that it will cost him $350 and he did not want to repair it, so he sold it.
Do you think that the 4.4V standby voltage can not cause any issues? It suppose to be 3.3V.
Another thing is, that the LED doesn't even turn on, that is controlled by the mainboard, no? That could be another sign, that the mainboard has some issues.
Maybe the technician swapped out the mainboard with a bad one and that is why it doesn't show the original problem. Just a thought.

[stj]

Re: Sony KDL55EX720 won't turn on

i suspect you have a shorted diode or voltage regulator.

[tom66]

Re: Sony KDL55EX720 won't turn on

It's plausible if the 4.4V is too high for a 3.3V standby it's damaged the main board.

[tibimakai]

Re: Sony KDL55EX720 won't turn on

At the diode at the standby transformer, the voltage is 4.27V, but at the output of the NJM2884U1-33 is the same thing. With everything connected, it shows 4.4V.

[stj]

Re: Sony KDL55EX720 won't turn on

that NJM2884U1-33 is probably shorted.
http://www.datasheetdir.com/NJM2884U1-33+LDO-Regulators

[tom66]

Re: Sony KDL55EX720 won't turn on

Yes I've had a shorted regulator before. And in my case 5V shorted to 3.3V and damaged the CPU, so I needed new main board.

[tibimakai]

Re: Sony KDL55EX720 won't turn on

So, I will order a new VDO and see what will happen after that, but most likely I will need another mainboard.
Thank you guys, I will let you know the outcome.
2nd 3D TV!

[tom66]

Re: Sony KDL55EX720 won't turn on

Missed a 42" LG 3D plasma for auction recently. I've not done one yet, I want to see what all the fuss is about.

[tibimakai]

Re: Sony KDL55EX720 won't turn on

For this one I paid the most, $180 without stand and remote. I had to drive 80 miles too, one way. It's very slow this business. I'm picking up Kenwood double dins, home theater receivers, monitors.
I had a nice 46" Samsung D series 3D, but the panel it was shorted at one side.
Stay away from the D series, to many problems with the panels.

[stj]

Re: Sony KDL55EX720 won't turn on

i wouldnt touch plasma's
i'v seen too many samsung ones that have a chain reaction taking out several panels when the screen fails or gets smashed.

[tom66]

Re: Sony KDL55EX720 won't turn on

I've just finished my 7th Panasonic plasma.

PZ80 (this one was a PZ85), these are AWESOME sets. And one very, very common issue which takes about an hour to fix. (10 blinks / 2 blinks MC module fault.) Picture quality - awesome. So, so bright, brighter than an LED TV, whilst having great overall performance.

Older Samsungs such as C96,97/Q96,97 etc, agreed, chain reaction, so I only get those free or very, very cheap. I got one free and fixed it, but it had sparklies all over the screen, which isn't fixable on older Samsungs.

The newer plasmas though aren't too bad, especially LG & Samsung, where the parts are available and fixes are reasonably easy. Just fixed a 42" LG PQ3000, bad PSU FETs, and a 42" LG PG3000 with blown upper buffer. Both cost less than £20 to fix.

[tibimakai]

Re: Sony KDL55EX720 won't turn on

How could I turn on the LEDs?
Here is the G8 board, which seems like it's a secondary power supply feeding the LED driver board.
http://www.shopjimmy.com/sony-1-474-302-11-g8-board.htm
I would like to see the screen, that it's OK, before I would order the mainboard.

[stj]

Re: Sony KDL55EX720 won't turn on

led's?

if you mean the tubes,
you need to have 12v going into the invertor,
then just put 3-5v on the p-on / lamp pin.
why? just getting the lights on wont tell you if the panel is bad.

[tibimakai]

Re: Sony KDL55EX720 won't turn on

Yes Leds, this is a thin 3D TV.

[stj]

Re: Sony KDL55EX720 won't turn on

well same thing,
you need power to the led driver board,
and a "power-on" signal.

[tibimakai]

Re: Sony KDL55EX720 won't turn on

That is my question, how do you do it on this TV? It's bit different, then other TVs that I have worked on.

[tibimakai]

Re: Sony KDL55EX720 won't turn on

Any ideas on how to turn on the LEDs?
I'm attaching the pictures from shopjimmy.

[tibimakai]

Re: Sony KDL55EX720 won't turn on

Bud, I have applied 3.3V at the T-Con_On and it turned on.
All the right voltages are at the G8(small PS), but at the output connector, there is no LED_VCC.
There are two pairs of diodes, at the output of the transformer and I'm not getting any voltage there.
There is a LED_On pin there, but I don't understand what should I do with that?
I have applied 3.3V, but the LED_VCC did not turn on.
Pictures are just for reference only, they are not clear enough.
At G8 board at connector CN6601 there is 12.71V, at CN6600 there is 391V, at CN6701 there is Reg_12V= 12.71V, BL_Err= 0.003V and ACC_OFF_DET= 4.4V.
Any help would be appreciated.