Touch panel issue

[hdonk]

Interesting - my screen from a previous batch has something similar down the left side. Ever since I replaced the LCD cable, the cursor arcs away from the middle of the screen on the left hand edge. I assume I've done something to that edge of the touch screen when (dis)assembling the unit.

I'm planning on ordering a new LCD when this latest problem is resolved

 

[EvilDragon]

Does this happen even if the screen is not in the case?

I don't have any without case left right now, but I'm pretty sure.

After all, they fully break, so removing them from the case afterwards still doesn't fix them.

It sounds like an overvoltage, but resistive touch layers don't even need that high voltage or power so that they could be damaged...

 

[Mr_Loon]

If it was a voltage issue why would it only manifest on the right hand side of the screen?

 

[EvilDragon]

If it was a voltage issue why would it only manifest on the right hand side of the screen?

I don't even think there IS much voltage involved at all, but I'll do some measurements here.

A resistive touchscreen panel is extremely simple.

It has two layers with four pads (X+, X-, Y+, Y-). When you push at a spot, the resistance changes and that's how the driver determines where you pushed.

It's nothing special.

And it gets worse the more often you move up and down on the right side, if it was voltage, it wouldn't get worse, it would simply make BOOM and stop working properly.

It sounds like something in the resistance changes when you press on the right side... doesn't really make sense, but we'll find out more .)

 

[Hồng Thất Công]

Don't send them back yet, as we first need to find a solution for them, especially as the remaining 400 LCDs probably have the same problem.

Either we need to change the voltage or the manufacturing company needs to replace these touchscreens, but it will take a bit to figure out how exactly to handle it.

You can use them for gaming until then and we'll replace them when we got 100% working screens.

I've also still got a lot of new displays here from the last batch which simply haven't been tested, so we'll have replacement ones here in 1 - 2 weeks.

We'll fix these things

The problem may only be lied in the touch screen panel and not the LCD.  Maybe try to replace one or two screens with the old touch panel see if it fixes the issue....

 

[Björn]

Hi,

I don't know if it has anything to do with the touchscreen issue, but sometimes there comes a weird static noise out of the speakers. It sounds like when you put your cell phone next to some speakers.

 

[TrashyMG]

Hi,

I don't know if it has anything to do with the touchscreen issue, but sometimes there comes a weird static noise out of the speakers. It sounds like when you put your cell phone next to some speakers.

Well when the amplifier powers off when idle for power savings, it sometimes makes a small barely audible noise.. 


I'm not sure if I ever heard a weird noise when placing a cell phone next to a speaker... do you mean if you place a phone next to a speaker that is outputting the audio, which causes a feedback loop?

 

[Björn]

OK, i just thougt i better tell everything i noticed^^ . 

What i meant was, when the speaker catches the phone signals it makes this static noise.

 

[EvilDragon]

Yes, it's clearly only the touch screen panel.

The display itself never was an issue for us - but we now have 360 self-destructing panels waiting in China

The question is: Why does it self-destruct?

I completely disassembled a touchscreen layer but couldn't find anything suspicious.

I made some measurements, maybe someone here has a clue...

We've got X_LEFT, X_RIGHT, Y_BUTTOM and Y_UP as pinout of the touchpanel.

Between X_LEFT and Y_UP, there's always 2,7V and when you press the panel, it goes to 0V.

Same for X_RIGHT and Y_BUTTOM.

Between X_LEFT and X_RIGHT and Y_BUTTOM and Y_UP, there's always 0V, except for when you press on the panel.

When you press on the panel, the voltage between X_LEFT and X_RIGHT varies between 26 and 51mV when you move from left to right and between Y_UP and Y_DOWN, it varies between 20 and 30mV when you move up and down.

When you move Up and Down a straight line, the voltage between X_LEFT and X_RIGHT doesn't change on a good panel (as you don't move left / right).

On the broken ones, I can clearly see a voltage change where it shouldn't be, so it's definitely the touchpanel reporting bad values to the driver chip.

Question is: How the heck can that happen?

I disassembled a screen, and it looks fine. No broken traces, no fluid or anything else that could cause that... well, something for the manufacturer to figure out, I guess.

 

[TrashyMG]

^ just eliminating the possibility, because I like debugging. Could it be an issue with the current boards? have you tried these LCDs on older boards?

Just to be thorough..

 

[EvilDragon]

^ just eliminating the possibility, because I like debugging. Could it be an issue with the current boards? have you tried these LCDs on older boards?

Just to be thorough..

Tried all kinds of LCD cables and boards (from CC over Rebirth to 1GHz).

It IS the LCD.

 

[TrashyMG]

^okay, just curious.. sorry I'm in a problem solver mindset today..

 

[Linux-SWAT]

Well, "congrats" ED, because that was tricky (and deadly for the screens) to find.

I have some spare RMA screens here in Paris in case no fix is possible.

 

[_wb_]

Just to give another data point: my new unit (sent on September 16th) does not suffer from the issue.

 

[ngrcat]

The unit I received on Wednesday (shipped September 19th) is fine except relatively small region starting about 1 cm above left bottom corner and ending about 2 cm further, here the touchscreen appears slightly decalibrated: I touch the left edge of the screen and the cursor shows about 0.5 cm right of it. Repeated calibration doesn't help. The rest of the touchscreen appear perfectly fine, I wouldn't even notice this if I weren't looking for touchscreen issues.

 

[Mr_Loon]

...

but we now have 360 self-destructing panels waiting in China

...

Is it possible to test some of these to ensure that the pretty unlikely possibility that the problem is introduced during shipping / manufacturing / assembly is not in fact the case?

How similar is the problem for units that use the new screen? Does it vary much between them or is the problem near enough identical for all units with the new screen?

 

[Stubie]

Same issue here!! Received my 1GHz edition on 25/09/13 in the UK (after a 3 year wait ), seemed ok at first then noticed that both sides were doing the same as the video post by Kettling.

Otherwise, delighted with the unit. Looking forward to a fix to complete the package.

 

[EvilDragon]

Well, as far as I know so far this is definitely a hardware issue. The touchscreen can even be broken like that when the unit doesn't have a battery inserted! We need to replace that one, sadly.

But we'll cover your costs, that's for sure.

 

[worzyl]

Oh dear! Will you be contacting the touch screen manufacturer to tell the good news?

They owe you for this mess.

 

[worzyl]

Hi ED.

Any news on the touch screen problem? Are you going to get the touch panels fixed first before re-stocking, or are the re-stocks that are coming, already have the issue fixed?