e701i-a3 no picture but backlights

[budwich]

Re: e701i-a3 no picture but backlights

something is funny though, if you say that you had no other cables connected but the LDVS cable connected and there was "smoke". I hope you are NOT measuring resistances with the board powered.

[tjmethod]

Re: e701i-a3 no picture but backlights

No. I don't even think I was touching anything when it did that. But the transistor ohmed that way before all that happened. I checked it first.

Tmal- if you are going to buy another t-con, buy it from Encompass parts- they have the green choice- they're boards come well packaged, new and it was the first time I actually got a faint 'V' before popping the COAXA transister. 'freak' suggested an alternative to the COAXA with higher values thus handling more resistance- he had pulled this specific transister from a sony t-con he had and said he was able to test the panel without blowing it and being able to pinpoint where the overlaod was coming from, do the panel mod and he said the tv's been working hassle free ever since- the transistor he used is a QF mosfet, 45v, 2A, SOT23- I bought 20 of them and since I now have 3 t-cons, I soldered them in the boards over the weekend.

[tjmethod]

Re: e701i-a3 no picture but backlights

Ok. Black probe in COM socket red probe right above it. Not the top socket. That's used for a different application. Have the selector switch set in the top left section in 200 DC mode.

Now with tcon connected to the LVDS cable only, run 2 screws into the tv securing the tcon to the tv. Don't worry about the metal cover being there. Now power up tv.

Put the black probe into one of the holes that are not occupied by a screw for your ground.

Now with the tv powered on, use the red probe and carefully probe those round matte grey canisters on the board. They say 3r3, 100 and 4r4 or something close to that.

Are you getting any voltage?

Ok so I tested all 3 boards last night.

On the the 1st board- 4R7- 1.0, 3P3- 3.1 to 4.6 (depending on which corner I put the red pribe on), 100- top left- 12.0, top right- 8.0 to 8.7, silver and red capacitor- 15.3


On the the 2st board- 4R7- top left-1.0, top right 1.3, 3P3- top left3.5, top right 3.1, 100- top left- 12.0, top right- 10.0, silver and red capacitor- 15.3

On the the 3rd board- 4R7- top left-1.0, top right- 2.8 to 2.9, 3P3- top left- 3.0, top right- 4.3, 100- top left- 11.9, top right- 10.1 to 10.3, silver and red capacitor- 15.3

I did not connect the panel ribbons, just the LVDS with tv turned on.

[freakaftr8]

Re: e701i-a3 no picture but backlights

Sounds like your boards are ready to go!

[tjmethod]

Re: e701i-a3 no picture but backlights

I ordered this one from encompass. I'm hoping they will allow me to return it or exchange it for another one that may possibly work.

If you ordered from Encompass, I highly doubt you got a bad board and if you at all had the LED drivers from the panel hooked up to the t-con with the set on, thats is what blows the transistor.

[tjmethod]

Re: e701i-a3 no picture but backlights

Sounds like your boards are ready to go!

Then it's phase 2 testing tonight- thanks and I'll keep you posted

[danandsteve]

Re: e701i-a3 no picture but backlights

Hi Freakaftr8, Are you saying by peeling the driver tabs off, your picture is as good as it was before the problem?

[freakaftr8]

Re: e701i-a3 no picture but backlights

Hi Freakaftr8, Are you saying by peeling the driver tabs off, your picture is as good as it was before the problem?

Yes. Do realize that this is of course irreversible blah blah blah. Last resort deal once you find out that the side with the issue is causing the failure.

But yes in all honesty the picture is just as good as I'm sure it look like before I picked it up. Of course when I picked it up it was dead.

The left and the right are doing half the cycle of what one driver tablet do on only one side. So essentially peeling off one driver tab on one side is going to cause the opposite side to do full duty cycle instead of half so yes it will probably wear out faster. But yet I have not seen a problem on mine and the kids use it at least 2 hours a day my wife uses it probably 3 hours a day so in total it's getting five hours a day use everyday for the last month.

[Tmal0146]

Re: e701i-a3 no picture but backlights

something is funny though, if you say that you had no other cables connected but the LDVS cable connected and there was "smoke". I hope you are NOT measuring resistances with the board powered.

I may not have stated that in the clearest way in my previous post. I checked the resistance on the transistor before I hooked it to the tv and got bad readings. So I thought I'd try to put it on the tv and hook up the LDVS cables only, just to see if i might get good voltage readings. Nothing else was plugged into the board yet and I checked voltage on the top canister labeled 3R3 when I removed the probe and was fixing to place it on the next canister I noticed a small bit of smoke come from the area around the canisters and the transistor. There's a possibility I could've accidentally touched something while I was checking the voltage but I don't think I did. But I contacted encompass and told them exactly what happened and they told me they'd send me a replacement board at no cost. So hopefully I'll have better luck with the next one.

[Tmal0146]

Re: e701i-a3 no picture but backlights

If you ordered from Encompass, I highly doubt you got a bad board and if you at all had the LED drivers from the panel hooked up to the t-con with the set on, thats is what blows the transistor.

I did the resistance test before I plugged the board onto the TV at all, and got bad readings on both pins of the transistor. One read like 2 and the other something like 10. I then plugged up only the LDVS cables to test voltage where I got bad voltage readings. And noticed the puff of smoke. After all this I determined I more than likely had a bad board but thought I'd give it a try anyways and unplugged the right side vertical driver cable. And did the test that freak came up with. Which of coarse was unsuccessful. Encompass gave me no hassle at all when I told them about everything and said they'd send me another board.

[Tmal0146]

Re: e701i-a3 no picture but backlights

But there is definitely the possibility that I accidentally touched something wrong while doing the voltage test that caused the smoke. Lol. But the bad resistance readings straight outta the box make me think it was bad from the get go. Tjmethod

[freakaftr8]

Re: e701i-a3 no picture but backlights

Ok. Next board just resistance check the transistor and call it good for testing. Then attempt to connect it up using the method I provided.

[budwich]

Re: e701i-a3 no picture but backlights

but maybe I am still the confused one. The only cables that supposedly should be plugged into the tcon are perhaps the "top two"... one of which is the ldvs and the other is the "powering plus other things" cable. The two cables going to the panel are not even plugged in so there should be NOT impact from any panel faults and the "thing" (tcon) should sit there... "semi happy". IF the Tcon isn't "stable" at that point, isn't this a sign of other problems as in other than panel????

[tjmethod]

Re: e701i-a3 no picture but backlights

Sounds like your boards are ready to go!

Well finally some results… I disconnected the lower right side LED driver ribbon then connected the ribbons to the bottom of the t-con, fired it up- nothing- black screen then backlights, so I turned it off, checked the 4r7, 3r3, 100 and silver cap- all read the same. I then disconnected the power repeated the original process with only the lower left 3/4" LED driver disconnected and finall the faint image of a partial 'V' in faint traces of red although it dosent show in the pic, then some horizontal flickering lines upper mid left of the screen. Then broken text in upper righthand side, then of course "no signal" in broken letters. So does this mean I need to peel the LED driver from the left side?

[freakaftr8]

Re: e701i-a3 no picture but backlights

but maybe I am still the confused one. The only cables that supposedly should be plugged into the tcon are perhaps the "top two"... one of which is the ldvs and the other is the "powering plus other things" cable. The two cables going to the panel are not even plugged in so there should be NOT impact from any panel faults and the "thing" (tcon) should sit there... "semi happy". IF the Tcon isn't "stable" at that point, isn't this a sign of other problems as in other than panel????

Yes. As long as a two white ribbons are not connected from the panel to the tcon then as far as that tcon is concerned it can run all day like that..

So essentially if you just have the two LVDS cables plugged into the T card from the mainboard and something goes south on the tcon then there is an official problem with the tcon board to begin with.

[freakaftr8]

Re: e701i-a3 no picture but backlights

Well finally some results… I disconnected the lower right side LED driver ribbon then connected the ribbons to the bottom of the t-con, fired it up- nothing- black screen then backlights, so I turned it off, checked the 4r7, 3r3, 100 and silver cap- all read the same. I then disconnected the power repeated the original process with only the lower left 3/4" LED driver disconnected and finall the faint image of a partial 'V' in faint traces of red although it dosent show in the pic, then some horizontal flickering lines upper mid left of the screen. Then broken text in upper righthand side, then of course "no signal" in broken letters. So does this mean I need to peel the LED driver from the left side?

All right now we're getting somewhere can you get something displayed on the screen like actual video footage of something? We'll go from there

But for now as it sounds you may have a left tab driver short on the left side of the panel.

[budwich]

Re: e701i-a3 no picture but backlights

Before you go the "final step", I would take the bezel off and "gently" look at the "under side" of the "tab cables" going from the panel to the edge boards on each side. IF you are lucky, you might be able to spot the bad cable by way of seeing things like "burn spots", "bad drivers chip", etc which will then confirm which side is bad.

[tjmethod]

Re: e701i-a3 no picture but backlights

Ok will have to check tonite on video, I've read where before where someone actually removed and replaced a section or thread of leds from the panel from another set and but if that were the case how would I know where to find which one or getting my hands on one. I can't recall where I read it but this was back when I thought the problem was a simple main board replacement. Are there other ways of fixing a short besides peeling the LED driver from the panel?
Thanks bro

[budwich]

Re: e701i-a3 no picture but backlights

I think you are "mis stating" things.... we are NOT talking about the "LED drivers"... those are things the provide the back lighting. The issue that most of this thread is dealing with or referring to is the "panel drivers" which deal with powering of the LCD elements.

[freakaftr8]

Re: e701i-a3 no picture but backlights

I think he means lcd drivers. Alot of people call them LED panel's because of the misleading sales pitches by retail outlets and manufatcurers calling them LED TVs making the public think that it's a true LED panel, not just the backlighting.

He's on the right path.