Author Topic: E701i-A3 T-con failure (Read 43051 times)

freakaftr8 · « **Reply #25 on:** September 08, 2015, 03:32:58 pm »

My new board should be here today. I'm fully expecting it to be bad. I however did remove the COXA 3 pin from my other board and it indeed shows shorted between pin 2 and 3.

sleepingAwake · « **Reply #26 on:** September 08, 2015, 04:05:03 pm »

I currently have 4 TCON boards on my bench.
2 Chinese boards, the original broken TCON and a used board I just received from a TV that would not have been in the affected serial number range.

All but the used board I just received show a short on COXA. Bear in mind the used board didn't work either however. Just the first Chinese board showed a pic for a couple mins.
I was thinking of flashing the firmware from the Chinese board to the oem I just received. Citing some sort of firmware mismatch. They are indeed different.

I'm supposed to receive a TCON repair kit that may include COXA. It arrives later today.

freakaftr8 · « **Reply #27 on:** September 08, 2015, 04:46:30 pm »

Awesome. Anxiously awaiting the results. And if the COXA is substituted for a different part let us know what that is.

sleepingAwake · « **Reply #28 on:** September 08, 2015, 06:06:50 pm »

Is there anyway to send output to the panel for testing purposes?
I still don't think it's a bad panel. I went over the panel and panel connectors and could find no indication of damage. Not that you'd always see an issue. Especially with embedded chips in the ribbon cables.

freakaftr8 · « **Reply #29 on:** September 08, 2015, 07:06:16 pm »

Well I just got some interesting information. Some of these boards i have heard have a co5a in place of the coxa. In this transistor reference to a 5 amp 60 volt NPN style made by RoHm. Cross reference is 2SC5103 it is either a SOT428 or a SC63 package.

The coxa mosfet is not cross referencable.

I'm ordering some right now

freakaftr8 · « **Reply #30 on:** September 08, 2015, 07:09:32 pm »

I personally don't know how to output anything to the panel that's not going through its timing board first. However I'm pretty confident the panel's fine as sharp panels rarely fail in when they do usually if you leave one connector on while the other ribbons disconnected from the t-con to the panel you should see a picture on at least half the panel.

Course that's just me personally finding panel faults that sharp usually seems to be the least amount of problems.

sleepingAwake · « **Reply #31 on:** September 09, 2015, 12:08:54 am »

The repair kit did not arrive today. Shows out for delivery. I doubt the postman works until 9pm.

freakaftr8 · « **Reply #32 on:** September 09, 2015, 12:18:17 am »

That sux. Well my board just arrived so let's do some testing. For the test that Coxa transistor before I even do anything else

freakaftr8 · « **Reply #33 on:** September 09, 2015, 12:27:09 am »

Ok first glance the COXA transistor is no longer coxa it is now COPA and the reading between pin 2 and pin 3 is 523 ohms not 2 ohms like the bad board. Yet it is still a Chinese board. In a few minutes I'm going to test it in the TV

freakaftr8 · « **Reply #34 on:** September 09, 2015, 12:42:43 am »

Ok. Board did not work. Now I'm getting 2.3 ohms between pin 2 and 3. This is extremely wierd. I did not hear anything pop or short out.

sleepingAwake · « **Reply #35 on:** September 09, 2015, 12:46:06 am »

Wow.
So what function does this component have?
If there is excess current being drawn through it where does it go?

freakaftr8 · « **Reply #36 on:** September 09, 2015, 12:53:04 am »

From what I can tell it apparently carries gamma processor ic voltages to the main processor. Probably could be the 1.0v Core voltage to the processor. There is another transistor showing a short too. The one to the left attached to the barrel capacitor. That is causing the capacitor to read dead short in an ohms test.

freakaftr8 · « **Reply #37 on:** September 09, 2015, 01:13:01 am »

This only leads me to believe that the gamma ICs are bad on these boards right out of the box. I can't see a failed EEPROM taking out transistors. But that's just me and maybe somebody else can chime in

freakaftr8 · « **Reply #38 on:** September 09, 2015, 01:41:40 am »

Not that this is going to help much but maybe. I recently scavenge parts out of a 55 inch Phillips TV that used a sharp panel. The t-con board is way different but the same in size in the pinouts to the main ribbon going to the mainboard are the same so I connected that tcon board to the main board and powered the TV up. I confirmed 12 volts 15 volts 3.3 volts and 1.2 volts working on that board so the main boards are obviously ok. I can't muster up the guts to try to connect it to the panel though because I'm sure it would damage the panel. But obviously clearly t-con board problem with these TVs not the panel

sleepingAwake · « **Reply #39 on:** September 09, 2015, 03:49:10 am »

Things did not go well tonight.

I decided to once again try the latest oem board I received.
Hooked it up and was surprised to see I had my 12v, 3.3v , 5v and 1.2v in all the right places.

I'm not sure if I only had one ribbon connector to the panel or both. I was fiddling with it more and checking for a picture and then I checked voltage again to find nothing but 12v into the dual mosfet AO4854.
No output. Dammit.
Checked COXA that was previously good and it's shorted. Double dammit.

The only good news. I found COXA on Aliexpress.

http://m.aliexpress.com/item/32378541068.html

freakaftr8 · « **Reply #40 on:** September 09, 2015, 04:37:55 am »

Wow you found it that's amazing! Good work. I'm going to look through my stash for a cross reference.

Rasz · « **Reply #41 on:** September 09, 2015, 08:15:25 am »

you do know the definition of insanity, right?
replacing that transistor is pointless if you dont locate the cause of failing

sleepingAwake · « **Reply #42 on:** September 09, 2015, 02:30:10 pm »

Your words could not be more true.
My mission is to determine what is causing these parts to fail.
Is it some transient event or excess current flow??? Could the panel itself be drawing to much current and blowing the components???

Unfortunately it happens so fast it's hard to tell. No excess heat was observed during the time of failure yesterday.

freakaftr8 · « **Reply #43 on:** September 09, 2015, 03:13:29 pm »

I'm on the same page as sleepingAwake. I'm not giving up.

The transistor replacement alone is not a fix. I'm down to find the root cause and I believe it very well may be a failed or semi shorted gamma IC. This is the Maxim ic that the transistors are against. It may have a high current draw causing these sub par components to fail prematurely due to reverse bias.

However last night I may be onto something despite that one transistor COXA being shorted which is a npn 60v, it is not receiving any voltage from the other bank of DC converter circuits. Which means the other two small transistors appear to be open. This means if they're open they are receiving 12 volts but not able to push anything out. I have one board that I'm messing with and I'm in attempt to replace those two open transistors with the equivalents. This will verify my findings if indeed the gamma processor is shorted it should take those transistors out right away. Boards are cheap and replacement kit are cheap as well so I figured it's a gamble but I'll give it a shot.

freakaftr8 · « **Reply #44 on:** September 09, 2015, 03:19:25 pm »

A couple months ago I was researching problems with Sony t-con boards in the KDL-46XBR6 model. This is a known failure t-con and what gets taken out are the positive and negative MOSFET in the dc-dc converter circuits they fail from excessive heat. Replacing those transistors alone doesn't fix it but the diodes short as well and sometimes some other discrete components on those boards. Manufactured by AUO for Sony. A lot of people are not able to repair them but I managed to successfully Repair 3 of them. It's all trial and error.

sleepingAwake · « **Reply #45 on:** September 09, 2015, 04:53:52 pm »

I don't know if it matters but I noticed the 60 inch version of this tv had a slightly different set of components. Most notably the transistor labeled coax seems to be replaced with a beefier component.
It's probably not pertinent.

http://www.ebay.com/ulk/itm/171909618790

freakaftr8 · « **Reply #46 on:** September 09, 2015, 05:16:12 pm »

Thats a good eye! Yes in fact people try to swap the 6-0 inch with the 70 inch tcon to find that it does not work. The 60 inch must use a different voltage DC DC converter system. I saw rthat too earlier. Im not sure exactly what they are doing with the board revisions, but the 60 iinch boards are failing the same way even with the bigger compoonenets I believe.

freakaftr8 · « **Reply #47 on:** September 09, 2015, 06:58:08 pm »

Well I broke down and ordered a repair kit.. Lets see what happens, im still messing with my test board though.

sleepingAwake · « **Reply #48 on:** September 09, 2015, 07:16:32 pm »

I'm still waiting on mine.
I was shipped up to Vermont in error and now it's making its way back here.
Good job USPS.

freakaftr8 · « **Reply #49 on:** September 10, 2015, 02:43:50 pm »

Yea I can imagine that is frustrating. I ordered my kit from Zemtronix out of Florida. Im in California, so this should be abbout 5 days.

I have found an issue with some of those transistors. They are mainly NPN style and I replaced the COXA and the X7BV, as that one seems like its getting 12v on pin 1 and 3 but nothing on the gate pin. That is a problem. The XOYV shorts and shows up on the SMD capacitor on the right. This transistor I replaced with an equivlent, and I had no voltages try to come up like before, probably to to the wrons saturation voltages.

The X7BV btw is not a transistor btw, its an N channel mosfet. Theres a problem here, something is disabling it.


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Author Topic: E701i-A3 T-con failure (Read 43051 times)

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