LCD Wells

omarale

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Hi everybody!, looking for schem of Wells gardner LCD model WGF3299-SIAS82G, 32 inch, DVI and VGA input, I´d really appreciate any help, thanks in advance
 
If Wells didn't release it, we don't have it. And I don't see it on their website. Send them an e-mail.

Really though, do you need a schematic? LCD driving circuitry is pretty simple.
 
The problem is that it has a random fail, two weeks ago, it failed everyday, last week only 1 time, the next was today since then. It doesn´t start with the first attempt of the day, but it does if you restart power. When fails, no backlight but cooler and power led works. I think it would have a PS issue but having the schem would be very helpful when you are trying to plan a smart way to follow up the fail, without only replacing components/parts and waiting to see how it results. If is not possible, I will try my best understanding to follow up the fail, today I leave the covers of PS and Logic PCB opened so I would measure when the problem appears. I also suppose any lamp of backlight would fail and so cut the voltage of all inverters... but I should be able to see the image shadow on the lcd panel, but nothing appears. Anyway, I´ll ask if they could send the service manual. Thank you!
 
check it over for bad caps, sounds like a ps /caps issue to me if it doesent turn on cold but then works once you try a couple times..
 
For sure check the caps in the powersupply.
And the voltages most if not all LCD boards
have the voltages written on the boards next to connectors
so just measuring the pins and compairing the posted voltages
is all you need to know.If not 24vs is most common needed for inverters.
If the 24vs and or voltages stay up when the backlights go out
then it could have a bad inverter board or bad lamps.
If you loose your voltages then you might replace the powersupply
If you don't have a video after shining a flashlite into the screen area
then you could have a loose LVDS cable or bad scaler/video board.
ALl depending your results from each test.
 
Results of check when fails: 24 volt present, 12 volt present, and there are only 2 connections extra power, one is inverters on/off and the other is brightness, in normal condition brightness is 1,9 volt, and backlight on/off is high. When fails, both are in 0 volt. I checked all caps in logic board and are ok. This is only powered by 12 volts, I found a missing 5 volt in internal regulator of this board, and following the circuit, it is commanded by Q2, an smd transistor that has 3,3 volt normally in base but this high isn´t present when fail. This is an output of U3, main and unique processor of pcb. I tried opening this pin and forcing the base of Q2 through a pull up resistor, and monitor start but with some stange shadows in screeen. Some times not. I think the only solution is asking a new pcb to wells, meantime, I won´t try anything else so it could be reseted when fails and let it work that way until get the part. Thank you all for the advices.
 
Never mind me. If you can force the backlight on, the inverters are good. Logic is crapping out on you for some reason, and that's usually really really hard to troubleshoot without proper SMT rework tools.
 
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I'm just curious as to how old this LCD is ?

Capacitor plague? Yeah, that's a very real possibility. He ordered a new logic board though, by the sounds of it.

omarale: If you get the new logic board and it's still fritzing out, replace all the electrolytic capacitors on the power board. You're probably getting ripple in your 12V, which a multimeter won't pick up.
 
Capacitor plague? Yeah, that's a very real possibility.

Not what I was thinking, but I know what you mean. And yeah, it could very well be crap caps somewhere.
I just wanted to know age in general since all the rage seems to be "slap an LCD in it" .... ya know ye ol' CRT vs. LCD debate. It might be worth tracking how long some of these newer LCD's are lasting.
 
Capacitor plague? Yeah, that's a very real possibility. He ordered a new logic board though, by the sounds of it.

omarale: If you get the new logic board and it's still fritzing out, replace all the electrolytic capacitors on the power board. You're probably getting ripple in your 12V, which a multimeter won't pick up.

I checked all caps in power bd, I also searched for ripple with scope. Even when I saw the fail in logic board, it was supplied from my working bench power supply. I could also replace or resolder main chip of logic bd, I have smt removal tools, but I guess the chance of get the chip is quite lower than the whole logic board. I suppose cheaper as well...
I ´ll see the part price first, if they ask much, I ´ll rather build a PIC logic to restart power if that 5 volt aren´t present...
 
I ´ll see the part price first, if they ask much, I ´ll rather build a PIC logic to restart power if that 5 volt aren´t present...

That's a stopgap solution at best. Intermittently failing to start isn't just a problem in itself, it's an omen -- it's going to fail outright.

Obviously the logic is shutting down for some reason. If voltages are good, you're looking at a bad IC or broken solder joint, though it could be a broken trace (highly unlikely).

A word of warning, most LCDs are built around an all-in-one IC that has some internal EEPROM. Getting the program off the old chip and into the new one could be pretty difficult or impossible.
 
there should be one or a few small lytic caps that are the startup caps.. i know it sounds dumb but it might be worth your time to replace those for shits and grins.
 
?

Got a picture of the boards in question?

I have more Fault Finding Techniques.

Things to watch for are:

How the power led reacts to things.
like is it always green never goes to orange red etc?

Disconnect the lnverter power and ribbon to inverters
then use a flashlite to see if any video on screen
i would agree if no video then its proably not a lamp or inverter problem.
more towards a bad t-con or scaler board,panel. you can't assume you need to check!

When you disconnect the lvds cable to the t-con board
the board at the top of panel, the cable from the scaler to the t-con..
remove it from the t-con then power up does the back lights stay on?


I understand the lamps stay up and video when you force it,but is the picture perfect
when you do this????? Got a picture of the image on screen with video and OSD??
is the brightness bright enough?
independent circuit troubleshooting can lead you towards a defective board or part
rather then TS a group of boards and parts at the same time.

There are tools to check inverters and lamps search the web for tools.
If needed,if you like send me the t-con and or scaler board and i will put it
in a working monitor to check it.Just pm me.
 
Thank you for your help and willingness, I `ve been removed from the case because this machine was in ¨conditional buy¨, so seller will have to solve the problem first and I don`t need to spend more time trying. Anyway I m not sure that stopgap would result successful, I can`t predict how logic would behave later considering actual problem....
Actually is like roothorick says, intermitent failing is an omen, I would add... it`s a bird of ill omen in this case where I `ve checked all possible causes. I found the chip is Genesis GM5621 and looking the poor data I could found on the web, reset is internal and don`t depends of external capacitor. So thank you very much to all for suggestions, help, I am sorry for bothering in vane, hope this would help smbdy at least.
Regards



Got a picture of the boards in question?

I have more Fault Finding Techniques.

Things to watch for are:

How the power led reacts to things.
like is it always green never goes to orange red etc?

Disconnect the lnverter power and ribbon to inverters
then use a flashlite to see if any video on screen
i would agree if no video then its proably not a lamp or inverter problem.
more towards a bad t-con or scaler board,panel. you can't assume you need to check!

When you disconnect the lvds cable to the t-con board
the board at the top of panel, the cable from the scaler to the t-con..
remove it from the t-con then power up does the back lights stay on?


I understand the lamps stay up and video when you force it,but is the picture perfect
when you do this????? Got a picture of the image on screen with video and OSD??
is the brightness bright enough?
independent circuit troubleshooting can lead you towards a defective board or part
rather then TS a group of boards and parts at the same time.

There are tools to check inverters and lamps search the web for tools.
If needed,if you like send me the t-con and or scaler board and i will put it
in a working monitor to check it.Just pm me.
 
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