Repair eBay LCD

T & T · 09-23-2005, 07:33 PM

As some of you know this eBay 7" "Super" monitor has had problems. I am asking for a little help from the Electronic's wizzards who may know the answer.

Currently my screen is blank and no image. After tracing the controller board, I have concluded that there is no power going to the LCD backlite. There are 7 pins on the inverter (I believe to be inputs) All show approximately 5 volts when testing with one exception. See the attached photo. The second pin from the far left (lower row of pins). I tried to test this point with several points on the board and no current travel.
Need help.

Thanks

T & T · 09-25-2005, 11:10 PM

bump!
Anyone?

greenman100 · 09-25-2005, 11:40 PM

Let me know if you decide to take me up on my offer

pRoFiT · 09-25-2005, 11:55 PM

Well the top left pin looks like ground from the picture. and the bottom one doesn't look like its going anywhere. Not sure about the top right pin. Looks more like an isolation transformer then a inverter. Well thats my $0.02

siliconkibou · 09-29-2005, 01:49 PM

I too, have the exact same problem.

Fuse looks good, but no LCD power after a day's use. (touchscreen still seems to work).

I also get no or negligable voltage on these pins which appear to run to the LCD screen/backlight for powering it.

I would be eager to know any helpful details as well.

One thought:

Would it be possible to power the LCD externally and bypass the seemingly faulty transformer/power on-board?

Worth looking into, I suppose...but then I'm a bit out of my league here.

-Paul

lanmanager · 10-08-2005, 03:27 PM

That transformer is the high voltage inverter. On the other side of that board is a pair of transistors that interact with the the grey coil on top. The inverter trades 12 volt dc high current for ~ 3000 volt? high frequency low current. Playing around with live inverters could send you flying across the room if not to the hospital. Fatal to those with weak hearts!!!!

Look at those large transistors. I'll bet one provides regulated 12 volts or so to the inverter circuit. I have this same on with a inverter transformer that glows when powered up.

Scouse Monkey · 10-08-2005, 04:09 PM

yeah be very careful measuring voltages out of that part of the controller.

the inverter will flash up to 1200V on start then then runs at about 600V once it detects the tube has fired.

1st you need to determin if the panel is running. hold the lcd at various angles and see if you can make out an image. use somehting witha high contrast to give youself the best chance.

if you cant see anything then check the fuse at the top of the controller in that flass tube. if you are getting a TS signal then that is unlikely to be the problem unless the TS is powered off the usb cable (i think the linITX does this so this one might too). The xenarc runs off the controller board.

Good luck. I will keep an eye out and see how you get on as fixing these controllers is a PITA and i would like to see if/how you fix it.

Scouse Monkey · 10-08-2005, 04:11 PM

Jerry and I were looking at that fuse and it does look blown.

try soldering a 1.5A fuse in and see, but make sure you observe antistatic precautions.

lanmanager · 10-08-2005, 04:19 PM

I have performed an autopsy on the smoked inverter I have. It appears that a plastic dialetric has broken down and allowed current to leak to the ferrite core. No help now as I have destroyed mine unwinding it looking for a short. Perhaps TOKO has a solution. Anyone know where I can get one of these?

http://www.toko.co.jp/products/ctlg/.../blc4110_e.htm

T & T · 10-08-2005, 08:04 PM

The glass tube fuse is good. Just checked it.
I am not getting any power to the LCD at all anymore.
When it first blew, I could still see the image, but it was very faint.
now nothing.

Scouse Monkey · 10-08-2005, 08:11 PM

Quote: Originally Posted by lanmanager

I have performed an autopsy on the smoked inverter I have. It appears that a plastic dialetric has broken down and allowed current to leak to the ferrite core. No help now as I have destroyed mine unwinding it looking for a short. Perhaps TOKO has a solution. Anyone know where I can get one of these?

http://www.toko.co.jp/products/ctlg/.../blc4110_e.htm

what you want to do is actually quite easy as the panel is the same as the one in the Xenarc....Disable/remove the current inverter (you may need the space so get your kacksaw out) and get an inverter for the xenarc from either someone with a broken xenarc or try digitalww or mp3car store. Then you need to find the inverter pinout yo be able to power it separately. and wire it up to the original inverter 12V supply on the PCB. i dont know off hand which pin is which for the inverter i am afraid. But someone will probably know. Getting the right tansformer is going to be hard unless it is labelled.

Scouse Monkey · 10-08-2005, 08:13 PM

Quote: Originally Posted by T & T

The glass tube fuse is good. Just checked it.
I am not getting any power to the LCD at all anymore.
When it first blew, I could still see the image, but it was very faint.
now nothing.

i dont know what to suggest for this. you may have really messed it up now!

greenman100 · 10-08-2005, 08:31 PM

Quote: Originally Posted by T & T

The glass tube fuse is good. Just checked it.
I am not getting any power to the LCD at all anymore.
When it first blew, I could still see the image, but it was very faint.
now nothing.

send it to me!

lanmanager · 10-08-2005, 09:06 PM

Thanks Mr. Lemon. Hows your son - lemon julian?

T & T · 10-16-2005, 01:12 AM

Well, I just got another controller board exactly like the fried board. Only problem is the brightness controlls do nothing and the LCD has very little back light (it is very dim with any amounts of sunlight, but can see the images somewhat clearly at night)
Anyone know which pins on the inverter to test or to jump to increase brightness?

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