Author Topic: Having a touch screen issue need help! s7800b  (Read 2894 times)

pieking83 (OP)

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Having a touch screen issue need help! s7800b
« on: October 22, 2014, 11:46:40 pm »
When I clean install new roms the touch screen is responsive, but after a few minutes of using the tablet the touch Screen starts to bug out and rapidly press randomly even when barely touched. I have been having this issue for awhile and stopped using the tablet because of this, but I decided to try again recently to fix this and no luck it still does the same thing after a few minutes of use. I want to get it working again to be able to play some games and for the upcoming rom releases.
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Joe Sixpack

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Re: Having a touch screen issue need help! s7800b
« Reply #1 on: October 23, 2014, 03:09:42 am »
so it shows random touches.. does this happen even when you aren't touching it?

sounds like either the touch screen is defective or maybe a loose cable.. pop the center plate off teh back and check the ribbon cable.

also the ghost touches.. are they places you already touched?
I get that on mine.. almost always it's when im running on just 1 core.
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GRiM

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Re: Having a touch screen issue need help! s7800b
« Reply #2 on: October 23, 2014, 10:13:53 am »
I had this issue when first installing CM11.  However my experience was the reverse,   the first few mins I had touch issues but after a few minutes or a reboot the issue was gone.
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pieking83 (OP)

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Re: Having a touch screen issue need help! s7800b
« Reply #3 on: October 23, 2014, 02:29:48 pm »
The issue I have noticed stopped after a reboot at least with a maetel Rom webclaws Rom 116 9 would happen with no fix. The touches seem to be only horizontal of where I am touching. The issue might be using the tablet while on the charger . This when the maetel Rom and webclaws Rom started to have this issue.
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sandwich

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Re: Having a touch screen issue need help! s7800b
« Reply #4 on: October 23, 2014, 03:39:01 pm »
Yes, phantom touches are normal in this device when charger is plugged.

It doesn't happen to everybody, but I've read several threads about people reporting this issue.

I've tried two S7800B and I also noticed this issue in one of them.

Sometimes charger also has to do, for example, mine is 2.5A, maybe it doesn't happen with 2A, I'm not sure.

Regards.
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pieking83 (OP)

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Re: Having a touch screen issue need help! s7800b
« Reply #5 on: October 23, 2014, 03:45:55 pm »
Thanks for the help I will have to charge it only when the device is off from now on
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hippy dave

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Re: Having a touch screen issue need help! s7800b
« Reply #6 on: October 23, 2014, 05:22:27 pm »
You might find it doesn't happen with a better, shielded charger. Common quirk with many brands of tablet.
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deysmacro

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Re: Having a touch screen issue need help! s7800b
« Reply #7 on: October 23, 2014, 06:38:19 pm »
Quote from: hippy dave on October 23, 2014, 05:22:27 pm
You might find it doesn't happen with a better, shielded charger. Common quirk with many brands of tablet.
Are you saying the common charger generates electrostatic?
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Joe Sixpack

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Re: Having a touch screen issue need help! s7800b
« Reply #8 on: October 23, 2014, 09:15:48 pm »
capacitive touch screens are sensitive, a dirty power source (unstable, ac leakage, RF) can cause them to act weird.

A good charger will filter out this stuff for the most part... you can sometimes pick up problems on car chargers inside old cars.. say anything mid 80's and older.

running a AC/DC charger on a modified sine wave inverter..

things like that.

I have problems on both of mine when running on 1 core especially if the system is busy I think it's missing touch screen events.. interrupt problems maybe.. I believe the WiFif or example is especially IRQ hoggy.

I sometimes get late touches or touches they stay on the screen (I have show touches on so I see everything)
the touch screens on these devices are pretty much trash imo, my sisters 40 dollar azpen tab with a PLASTIC SCREEN stomps a mutt hole in my 78 as far as touch screen accuracy and sensitivity goes.

If you're getting random presses in places you had not pressed then I'd say it's either defective screen, loose ribbon cable, or as was suggested your charger making the touch screen jittery.

Jitter should not happen on battery though.
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hippy dave

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Re: Having a touch screen issue need help! s7800b
« Reply #9 on: October 23, 2014, 11:14:50 pm »
Even with branded chargers that came with half-decent phones by manufacturers you've heard of, we've found that some send a tablet's touchscreen wonky and some don't. I wouldn't expect much from no-name chargers from China.
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pieking83 (OP)

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Re: Having a touch screen issue need help! s7800b
« Reply #10 on: October 24, 2014, 06:05:27 am »
Thanks for all of the information
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plymouthbiker

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Re: Having a touch screen issue need help! s7800b
« Reply #11 on: October 07, 2015, 01:02:42 pm »
I'm having the same issue. Random app presses and scrolling. Would a screen earthing issue be a reason for this. Where is the earth on this device and could it be reinforced. Also, I've heard information on dodgy screens can be due to components that touch the screen such as cables etc and static. And have been fixed by using insulation tape or reinforcing earths from the screen. Although this has not been reported on the JXD 7800 but things such as the One plus one mobile/cell phone and the HTC sensation Mobile/cell phone.

Could this be a possible reason for random erratic touch screen issues?

I've got a second hand 7800b which I know has this issue and therefore been searching the net for information.

If I find out the reason I'll let you know. Time for a bit of electrical surgery i think..
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