e701i-a3 no picture but backlights

[tjmethod]

Re: e701i-a3 no picture but backlights

I don't believe the panel will technically show anything if both driver boards are disconnected. at least one side must be connected in order to display the trailing horizontal lines that a control. Due to the fact that this effect is not built into the vertical drivers like other panels

You are right I definately dont want to buy anympre t-con boardsl- do you or anyone got a line on where I can buy transister with a bit stronger values like the sony one you found. I also need that silver capacitor- both of these are blown on 2 of the 3 boards I have- I hadnt tested one that I know at least has the blown COXA. So from what I have read earlier, it is i fact the panel blowi g the Coxa… and the silver capacitor?. Has your or anyone tried a new or good powoer board since the power boards have the LED inverter on them and whats your thoughts on that?

[freakaftr8]

Re: e701i-a3 no picture but backlights

Actually the panel is blowing only the transistor. The capacitors are ok.

The power supply on these sets are quite hardy. If its got backlight and powering up the power supply and mainboard is ok.

The primary problem is one or more side drivers fail and overload the tcon. In turn that COXA transistor seems to be the failure

[tjmethod]

Re: e701i-a3 no picture but backlights

Two of my t-cons I tested after the fact had no reading on the silver capacitor in dc mode like you said. Any idea what could be blowing my silver caps? If I get another good or repaired t-con in, should I try disconnecting the lower left first or or just get a beefier coxa- the specs you gave me earlier- from what I recall, sot 23 n-channel 45v 2a- I couldnt find anywhere online… I am thinking I can find the cap. Do you know the specs on the one that came out of the sony you had in your stash?

[freakaftr8]

Re: e701i-a3 no picture but backlights

The capacitors are ok. Trust me. I only mentioned testing the voltage across that silver cap because if there's voltage there than the COXA transistor is ok and the t-con board is providing all voltages required to operate properly. The silver capacitor is just a test point

[tjmethod]

Re: e701i-a3 no picture but backlights

The capacitors are ok. Trust me. I only mentioned testing the voltage across that silver cap because if there's voltage there than the COXA transistor is ok and the t-con board is providing all voltages required to operate properly. The silver capacitor is just a test point

Ok… since the transister is blown is why I get no reading on the cap?

I am trying to find a beefier transister- do all the following fit the specs you had mentioned earlier? The last one is 3a- will that handle more power?

[freakaftr8]

Re: e701i-a3 no picture but backlights

Okay the reason you get no reading on that cap with a blown transistor is because it's shutting down the voltage in the board. With that transistor shorted all of the voltage is beside the 12 volts going into the t-con are now shut down. Like I said before I use that capacitor is a testing point to see if the transistor is good and the rest of the board is putting out proper voltages.

I as well are looking for a suitable transistor replacement for you guys. Stay tuned

[freakaftr8]

Re: e701i-a3 no picture but backlights

Found it coming out of China unfortunately but this is the one that I used

QF which is a RTR020N05 2a 45v n channel SOT-23 style mosfet

m.alibaba.com/product/60290702860/RTR020N05-020N05-MOSFET-N-Channel-SOT.html

[tjmethod]

Re: e701i-a3 no picture but backlights

Yup RTR020N05 comes back to a 45v 2a n-channel sot-23 made by ROHM, I ordered 20 that just shipped from TX under $13 and $4 shipping- should have them Thursda.…

[freakaftr8]

Re: e701i-a3 no picture but backlights

Ok great!

[Tmal0146]

Re: e701i-a3 no picture but backlights

Hey guys. So I'm new to this forum. But I have the same problems as listed above. I have audio, but no video. Backlight is still coming on, but I have no picture. All I have when the TV is powered on is a dull very faint blueish screen. I am not very experienced when it comes to working on TVs but I have done a lot of research on this issue with this model TV. I have read every comment on this thread and I'm going to walk through this to make sure I understand correctly what needs to be done to "fix" this TV. I have the back cover and sides off and I have unplugged the small white ribbon on the bottom right corner of the screen. I now need to replace the tcon board or the transistor that is blown on the board and with the white ribbon that is feeding the side driver boards unplugged I now need to power on my tv to see if it is in fact the right side drivers that are defective. Once I decide that I'm on the defective side. Do I simply just peel the gold looking ribbons from the panel and remove both of the driver boards from the side that I determine is defective? Is there anything else that has to be done to make it work? I will post a couple pictures if needed.

[freakaftr8]

Re: e701i-a3 no picture but backlights

Sounds like you are right on par!

[Tmal0146]

Re: e701i-a3 no picture but backlights

Awesome! Thanks a bunch! Next question is. Where is a good reliable place to buy a tcon board?

[freakaftr8]

Re: e701i-a3 no picture but backlights

Lol honestly I can't tell you. I believe a lot of these sales outlets are selling rubbish t-con boards that were deemed as panel failure but the boards were okay. Yes they are half correct the panels did fail however it took out the boards with them and what I have found is purchasing these boards most of them are already failed. Your best bet would to repair your board.

If you don't have the means necessary then it's a gamble wherever you get the board from.

before you connect the board to the panel just connect the LVDS cable. From there you can read voltages on the board following earlier posts to make sure the boards working or not before you connect it to the panel

[Tmal0146]

Re: e701i-a3 no picture but backlights

Ok. I'll try to grab one from somewhere and do exactly that. I really appreciate the help and I'll take pics and update the thread on how things end up going.

[12345lonestar]

Re: e701i-a3 no picture but backlights

If the transistor is not yet bad, you may be able to power it up with the ribbon removed as Freak stated. If that is good then try the surgery on the panel, removing the ribbons. Please note - this is a last resort. It is not a reversible operation. If you do something wrong, the TV is not fixable past that point.

Not sure if this ha been covered but I do not recall. So if you remove the cable form the side driver boards, wouldn't they be disengaged and not cause the issue anymore? So why does removing it completely change anything. Since they are already unplugged. Just wondering why removing it is necessary to complete the repair. Jut want to understand whats going on.

[freakaftr8]

Re: e701i-a3 no picture but backlights

Because if they're still connected to the panel they're dragging down the opposite side drivers which is causing them an abundant amount of load too much that they can handle by themselves which in turn will burn those out. Also the panel cannot drive those tabs without the power being connected so they will drag the panel down causing it to be dark on that side. Plus the reason they are being removed in the first place is because one shorted we can't have that connected to the panel.

[Tmal0146]

Re: e701i-a3 no picture but backlights

Not sure if this ha been covered but I do not recall. So if you remove the cable form the side driver boards, wouldn't they be disengaged and not cause the issue anymore? So why does removing it completely change anything. Since they are already unplugged. Just wondering why removing it is necessary to complete the repair. Jut want to understand whats going on.

I wondered the same thing but just assumed something like what Freak says.

[12345lonestar]

Re: e701i-a3 no picture but backlights

Agreed. You can replace a coil but I would use a dvm in diode test mode. Although you can achieve results with your meter you can't have the power on while you do this.

Here's a thought. Just test power at this point. If you have 24v or so the + side of the silver round capacitor on the left side of the board in the picture your ok. Test it like this turn your voltmeter to DC voltage and use the red lead against the plus side of that capacitor the black lead against one of the screw lug terminals on the tcon board. If you have voltage there the rest of the board is functional and you can use it.

I tried this test with my T-con and got 0 voltage. Is this indicative that there is something more wrong with it than just the MOSFET chip? Should I just get a whole new t-con board rather than replacing the MOSFET?

[freakaftr8]

Re: e701i-a3 no picture but backlights

Well is there a short showing up in the COXA transistor?

[12345lonestar]

Re: e701i-a3 no picture but backlights

I tested the resistor and it did not appear to be shorted. I got normal readings from it. So I was a little surprised when I did not receive any Voltage on the silver round resistor from this test. But I am having the blank screen issue. I tried disconnecting the white cable from either side and nothing changed. Still blank black screen. But everything else points to it being the bad horizontal video driver.

I was originally going to replace the resistor on my t-con, but now i'm not sure what is damaged on it since it failed the test but the resistor does not appear to be shorted. I suppose Ill buy a new T-con and see. Ill buy some resistors too since many of them seem to be damaged on the boards being sold online.