Cross a sharp LCD TV with a BenQ, what would you get? (Part 1)

Discussion in 'General Electronics Chat' started by R!f@@, Jun 2, 2009.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
    A few sleepless nights and a few HV shocks in between, I'll say.

    This is not a tutorial nor a recommendation to any one with a faint heart
    but something that I would like to share

    Saying that I would begin what I have been through in the last whole week to get myself a free 26" LCD TV.

    A couple of months back I started working on a Sharp Aquos series 26" LCD TV, ( a pic is shown below)

    This one came in for repair. Fault was that the darn thing goes white after turning on and sometimes does not even show a display and after a few secs goes to standby. Now I have attended LCD's before, mainly monitors and a quite familiar with the back lit and panel drive technics like LVDS,
    But this was my first attempt on a huge LCD TV, and had no idea what so ever to expect about it's principle of operation.
    I was having a field day with the TV Since I cannot find any thing wrong with the components. I was beginning to think I had met my match.
    As you know I never give up on anything, so I though I'll tackle the problem a bit later and do a bit more research on these Aquos series and to my surprise I could not find any thing on the net about the problems I am having. So I was getting no where.
    To my luck a friend of mine drop by during my second attempt on the darn thing and he said he has one just like it and it's missing a part of the screen. So naturally he agreed to bring it, I though at least if this TV shows a picture I can switch the boards to pinpoint which part is creating the white screen.
    So after switching every board here and there both of them were having the same faults as before. So now what.
    Well, now at least I know that none of the boards had any problem in the first place so I must go deeper.
    So it was time to dismantle the LCD Panel itself, and to my surprise the fault was same for both the panels even though they show different faults.


    This Pic is for refrence
    Above is the LCD panel of the BenQ TV. You can see the column drivers at the bottom and the row drivers to ur right. Now the two panels a quite same except the PCB connection to DSP are different.


    Now the above is a closeup of the column driver connection the PCB. Notice the flexible rubber like thingy and with in it the driver chip. Now in between the PCB and the rubber connector is some king of conductive glue which is thermally bonded. This picture shows the benQ one, but the Sharp ones has the connection broken and oxidation was formed degrading the connection and creating intermittent faults. A little figure pressure on the connection and Viola.!!! A perfect Picture . Now why did not I think of looking at here before. well, I guess there is a first time to everything .

    But there is no way for me to bond these connection, a little from the soldering iron damages the rubber. Bummer.

    So all is lost with both of them. The final conclusion was that the heat generated from the panel causes the glue to melt, the panel was obviously used in places without AC. and is not designed for our environment.
    The best part is this friend has brought 3 more of these TV's and all of them has the same stupid fault. So now I'm stuck with all of them, and there is no way for me to get a new panel so far. The guy left the TV's for me to experiment on.

    Till last week a cousin of mine said his TV goes to stand by after a few secs. and asked me to repair it, so naturally he brought it and to my surprise it was a 26" LCD TV. It shows a perfect picture at cold start for a more that 10 secs and goes to stand by and after that it would stay on for a 2 or 3 sec.

    So I started to work on it, and the problem was in the inverter Assy. A bad inverter transformer was creating all the problem, so it seems.
    Here (Above) you can see the Tx removed and it seems that one of the secondary winding was open circuit. The wire uses was so thin that even a slightest finger pressure cause it to break, Now how in god's name am I going to wind a couple of thousand turns of these wires that I could hardly hold. [​IMG]. It was next to impossible, So I thought of bypassing the Tx to get the Inverter working without it shutting down the TV. But before that I told the owner about the problem and the best way is to get a new Inverter Assy, which is not possible even though I said it ( these things a typical in Maldives ).
    This whole Idea of me combining both BenQ and Sharp TV came to me when he said that he will buy a new one and that I can do what ever I want with it. Music to my Ears
    At first I thought of Using the Sharp Inverter Assy instead of the BenQ one, since both are of same size and has the same no. of tube connections, I never gave a second thought of how much the tubes needed to operate.
    I always do and think later.
    Above is the Sharp back removed.

    Part 2

    Last edited: Jun 3, 2009