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Kronos 73 1st gen Touch Screen Problem - Any Ideas - Help?

 
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Jo Borges



Joined: 18 Mar 2021
Posts: 4

PostPosted: Fri Mar 19, 2021 12:31 am    Post subject: Kronos 73 1st gen Touch Screen Problem - Any Ideas - Help? Reply with quote

Hi, I have a Kronos 73 by about 4 years, the display get bad pixels and about a year ago, the touch started to malfunction, from nothing. One day it was ok and the next day the erratic behavior start to happen.

Since my display had bad pixels I ordered a new one, with touch, from Ali

It worked like a charm, just to see that the touch has the same erratic behavior, it's a brand new one work exactly like the defective one.

So, I thought I was bad lucky and try to order another one, this time just the touch, and tried this one without success.

So I just forgot about it.

in the Last months I was wanting to use the Kronos in some of my productions and try to order a new touch screen from a different user and different brand, and after install it I get the exact same behavior with this touch screen.

The error is that the touch is receiving the input all out of place, pls see the video.



And this was equal in all cases, since my original touch become defective.

And exactly by this problem, I can't calibrate it on the service screen since it not receive my input in the place that it needed to be.

So I would like to ask you guys, especially the tech and electronics experienced ones, what is your suggestion, besides to bring it to technical assistance. I will, for sure, as a last resource, but would try to avoid it because of pandemics, and really high rates for tech assistance and replacement parts here in Brazil.

So, before try every known and possible solution, or even a home made fix, I would avoid a authorized Korg center here.

I reinstalled all the system fron ground up yesterday, and that was bad, was my last resort, but now, I can't update to the latest version of system, because this routines needs confirmation from touch the screen where mine isn't receiving input, BTW, why in the world, as the Kronos is nothing more than a PC running a proprietary system, Korg would not implemented USB mouse and keyboard input support in Kronos, just WHY? And yet, why in the essential system routines, Korg didn't let us do all by physical keyboard input, even if it was a bad way, but at least a n alternative way of input and choose screen options so you can adjust and make some routines with a malfunctioning touch screen?
That would really help in such situations.
Anyway, I'm asking for help

Some questions:
1 Did by chance, someone faced this exactly problem with touchscreen?
2 Could it be a bad motherboard?
3 Could it be some some touch screen controller board, if Kronos has this? If it has one touch controller board, which one do this job?
4 Could it be some kind of bad bios on motherboard? If so, is there a way to try to fix this?
5 What did you guys suggest me to do? ANy help or tips would be great appreciated.

6 If I understood correctly, in the service manual, there's a section where it instruct to 73 users like me to have a "LCD Spacer" and I know my Kronos didn't had one, so why we had to put this after change the touch? And if we need this to the new touch work properly, why it wasn't there in the first place? Could that causing all my Touch problems?

Kronos-1

I love my Korg Kronos, I'm missing it, so I will be very grateful for any help or tips.

Thanks in advance.

Jo Borges
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I would like to have USB mouse and Keyboard support on Kronos Keyboards


Last edited by Jo Borges on Fri Mar 19, 2021 3:46 pm; edited 1 time in total
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KK
Platinum Member


Joined: 13 Oct 2016
Posts: 961

PostPosted: Fri Mar 19, 2021 2:11 pm    Post subject: Reply with quote

Jo Borges wrote:
Some questions:
1 Did by chance, someone faced this exactly problem with touchscreen?
2 Could it be a bad motherboard?
3 Could it be some some touch screen controller board, if Kronos has this? If it has one touch controller board, which one do this job?
4 Could it be some kind of bad bios on motherboard? If so, is there a way to try to fix this?
5 What did you guys suggest me to do? ANy help or tips would be great appreciated.

6 If I understood correctly, in the service manual, there's a section where it instruct to 73 users like me to have a "LCD Spacer"

Hi there,

About your questions, this has nothing to do with the motherboard nor the BIOS. Also, the LCD controller PCB is right behind it when you change the screen. It is attached there with two screws which has to be grounded to the rest of the Kronos chassis. The metal parts ensure the contact is made.

After looking at your video, you problem seems related only to the touch part of the screen. Such a behaviour can sometimes happen if there is a resistive problem with the touch surface. I would start by removing the screen from its hood/holder and clean everything there very carefully to eliminate any possibility of resistive interference caused by dirt between the lined contacts there, etc. Especially what is covered by the angles and corners of the hood/holder. Check to ensure if any damage appears there, those linings are delicate, same with the junction between them and the beginning of the copper ribbon. These must be free of dirt and never pressed or handled too hard. Check also in the inside edges of the hood/holder while the screen is out. Any bump or tiny thing there can end up causing a problem if it creates a pressure where it should not.

When reinstalling the screen, it must be fixed there carefully without any excessive pressure on any side. If possible, test the screen outside of its hood/holder to see if it could be the cause of interference. If nothing helps, another thing I would do is to use some contact cleaner inside the CN21A female connector on the controls PCB where you insert the 4-wire ribbon going to the touch interface (which serves the X-Y coordinates). Then I would use a tiny nail file and very gently polish the copper endings of that ribbon's wires just a few times to make sure there is no trace of corrosion there possibly causing your strange X-Y offset. Then reinsert the ribbon correctly to the bottom of the connector.

If this problem would not have happened by itself, I might have concluded from your video that it looks as if someone inverted the X-Y ribbon in its socket. The order of the wires is : RIGHT, BOTTOM, LEFT and TOP so if it would be inverted, you would obtain coordinates for a screen turned 90 degrees clockwise and then turned again face upside down in its Y axis. Razz Or in other words, left at the bottom and right at the top, with bottom at the left and top at the right. Not very practical !

But of course, it is unlikely the case and more a resistive/interference problem somewhere on the top part of the LCD screen where the touch pad resides. Keep us posted to tell if anything could help.
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Jo Borges



Joined: 18 Mar 2021
Posts: 4

PostPosted: Fri Mar 19, 2021 3:44 pm    Post subject: Reply with quote

Quote:
When reinstalling the screen, it must be fixed there carefully without any excessive pressure on any side. If possible, test the screen outside of its hood/holder to see if it could be the cause of interference. If nothing helps, another thing I would do is to use some contact cleaner inside the CN21A female connector on the controls PCB where you insert the 4-wire ribbon going to the touch interface (which serves the X-Y coordinates). Then I would use a tiny nail file and very gently polish the copper endings of that ribbon's wires just a few times to make sure there is no trace of corrosion there possibly causing your strange X-Y offset. Then reinsert the ribbon correctly to the bottom of the connector.

If this problem would not have happened by itself, I might have concluded from your video that it looks as if someone inverted the X-Y ribbon in its socket. The order of the wires is : RIGHT, BOTTOM, LEFT and TOP so if it would be inverted, you would obtain coordinates for a screen turned 90 degrees clockwise and then turned again face upside down in its Y axis. Razz Or in other words, left at the bottom and right at the top, with bottom at the left and top at the right. Not very practical !

But of course, it is unlikely the case and more a resistive/interference problem somewhere on the top part of the LCD screen where the touch pad resides. Keep us posted to tell if anything could help.


Hi KK, thank for your feedback and ideas to help.

I think I'll try to test the touch outside of the holder to see if it's some kind of pressure related, and talking about this, did you saw that part of service manual, where they say we have to install a LCD Spacer? Questions 6. it's a part that could be ordered from Korg btw, and I thing this a very strange topic there. Could the absence of this item causing my troubles maybe?

I'll try to open it today an investigate further your suggestions.

Thanks
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I would like to have USB mouse and Keyboard support on Kronos Keyboards
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KK
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Joined: 13 Oct 2016
Posts: 961

PostPosted: Fri Mar 19, 2021 5:07 pm    Post subject: Reply with quote

Jo Borges wrote:
Hi KK, thank for your feedback and ideas to help.

I think I'll try to test the touch outside of the holder to see if it's some kind of pressure related, and talking about this, did you saw that part of service manual, where they say we have to install a LCD Spacer? Questions 6. it's a part that could be ordered from Korg btw, and I thing this a very strange topic there. Could the absence of this item causing my troubles maybe?

I'll try to open it today an investigate further your suggestions.

Thanks

Hi there,

You are welcome and hopefully you will be able to find the cause and correct it. About the spacer, I saw that too when I read the service manuals some years ago, and thought it was a bit weird. I would not worry about this for now and instead very gently but thoroughly clean the screen top and wired linings to the touch device and also inspect for any kind of dirt possibly causing a resistive X-Y position shift and also removing any unevenness or tiny particles under the hood/holder and on the screen edges resting against it which could cause a similar physical interference.

Definitely, if you can test the screen out of its hood/holder, that could point you in some direction for what to do next. You could for example rest the LCD on its back on a gentle clean non-conductive surface - for example, a piece of cardboard. Make sure the metal parts around the screen don't suddenly fall out and short something. Push very gently on the screen using your fingernail instead of fingertips to pinpoint a given spot on the LCD and also apply least pressure possible on the rear PCB attached to the screen back. See if screen X-Y coordinates suddenly get better or just fine with correct reaction on screen. If so, there is interference under the screen hood/holder causing the problem. Otherwise, there could be oxidation on the 4-wire connector/ribbon, etc.
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