Fanuc 8.4" LCD Wonky

I have a 1995 Fanuc Robodrill T10B with 16mb controls. It has a 8.4" LCD that has issues. When I turn on the machine the right side of the screen is pink. The left side looks good. After 5 min or so the right side starts to show text but flickers allot. Another couple minutes and the screen evens out mostly. There is a distinct shading down the middle of the screen and the right side is slightly blurry. Sometimes the Right stays pink. Sometimes it turns black like the left side. Any suggestion of what to look at and how to fix? I re-seated all the cables. The soft buttons seem to work. All seven main screens work. Just the display is wonky. Is it the LCD or the Card above it? Or both? I just sank every penny getting the machine home. I don't have $1000 to change a screen.
I have seen some old posts of people upgrading there old CRTs to LCDs. Is there a cheap way to do this?

Donny

This probably won't help, but check the ground to the display. I had something similar happen to a truck radio LCD and that was my solution.

Check to see if there is a ribbon cable for the display that plugs into a motherboard.

Had the same problem with a 31ia5 control.
Re plugging the cable fixed it.

The kind of artifact seen in that picture suggests the column drivers are on their way out. It's possible that it's a bad cap problem or perhaps a cold solder joint that fixes itself after a while.

LCDs are driven by a bunch of really big chips that have a lot of pins, each pixel requires a matrix of row/column drivers. So if that 8.4" screen is something like 640x480, there are 1120 individual drivers and pins from the controller chips.

The pins connect to the glass substrate of the LCD via traces printed on the glass, which could also be suspect.

The simplest way of diagnosing these things is to make sure all cables are reseated, then press on each of the big chips to see if it affects the screen. If that doesn't do anything, then it's more likely to be an electrical issue with bad filter caps on the main LCD control board.

An LCD like that probably uses a 18bit digital VGA type signal, so the input signal would not have the type of effect on the screen, meaning it's not likely to be the cable between the display and the control.

The fact that time is a factor indicates heat is a factor and that once it warms up, the problem slowly fixes itself, which in itself points to a cold joint. Bad capacitors typically manifest as failure to startup correctly because the voltage to the device is not within the specified range during reset.

Took it apart. Reseated all the cables again. Looked for bulging caps and bad solder joints. Couldn't see anything out of place. I had not seen Perry's post when I did it so I didn't try pushing on the chips while powered.
After playing with it for most of the day. (new machine trying to figure out how to use it) The screen does not always come up the same. Sometimes the right Pink, Now White side stays white. Sometimes it goes blurry and overwrites stuff on the right side. Sometime it comes up only slightly blurry. Usually one or two power cycles and I can mostly read the screen. Some characters are still missing bits but mostly there.
Maybe like you said I have a bad cap.
Does anyone know what key combination turns the screen off and on without cycling main power? Read it somewhere last week but can't find it now.

Donny

Not sure, but try this to clear the screen:
Hold down CAN key and press any function key such as POS.
Press any function key to restore the screen.

thanks for the buttons to turn off the screen. Unfortunately it did not make a difference. Only a cycle of power can change how bad the screen is. So I think that means the issue is in the fanuc controller board and not the Sharp LCD. Thats a expensive problem.

Donny

Sounds like a bad capacitor to me, if power cycling it makes a difference.

Looking at the board I wonder if the part on the lower left has been replaced or someone tried to super glue it in place. Not sure if they glued things like this in 95. What do you think. See red square.

Perry Harrington said:

Sounds like a bad capacitor to me, if power cycling it makes a difference.

Click to expand...

DonnyM said:

Looking at the board I wonder if the part on the lower left has been replaced or someone tried to super glue it in place. Not sure if they glued things like this in 95. What do you think. See red square.
View attachment 168725

Click to expand...

That's typical. That looks like the HV ballast for the CCFL backlights.

It looks like you have 4 electrolytic capacitors on that board.

The caps fail in several ways, all of them can be deduced with an ESR meter to check the equivalent series resistance. IF the ESR is too high, it indicates a bad cap. The ESR differs based on the cap voltage and rating, most cheap ESR testers have a chart on them telling you the acceptable range for a cap of a given voltage and capacity.

You may want to purchase an $80 ESR tester off amazon/ebay and test those caps first, before settling on those being the problem. An ESR tester can test caps in-circuit, so you just remove the board and probe the leads on the back side.

I'm guessing there is another board on the LCD itself which has drivers for the LCD, there doesn't seem to be the typical VLSI logic or enough wires coming off that board to actually drive the LCD segments.

Perry,
Thanks for the info. Attached is a image of the board on the LCD itself. I have one coming to see if that fixes it. Was $50. They were also used in Toshiba laptops back in the day. After looking at the Fanuc board on top the area that I put the red square around I believe is only for the back light power. So the hot glued cap shouldn't be a issue. If the new LCD does not fix it I will see about getting a ESR tester. Or maybe just replace the caps since cost right now is a major concern. I blew ALL of my money and then some just getting the machine home.

Donny

The good news is the $49 Sharp Monitor fixed the display. So the Fanuc Board was not the problem. By taking it apart and chasing part numbers I saved $2800. Yesterday before the new monitor showed up I powered it up to find a 910 SRAM Parity (4n) Error. The machine came with no Parameters and my cable hadn't showed up yet so I couldn't back them up. Looks like the only fix it to clear the memory and enter the parameters. But I have none. Now what?

Donny