Gearbest 3.5 Screen Variant B?

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drafterITA
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Gearbest 3.5 Screen Variant B?

Post by drafterITA » Fri Mar 10, 2017 9:43 am

Hello Community :)
I got most of the parts I want for my first build, including the screens from Gearbest.. I looked on the Sudomod Wiki and my board looks a bit different from the one showed, with the 5V modification. I can guess the connection i need to make, but I'd rather be sure and not mess up straight away :)
Is there some one that can offer assistance? I took HD pictures of it.. and there they are!

[spoiler="Gearbest screen board"]Front
Image

Back
Image[/spoiler]

Thank you very much!!

Edit: img uploaded on imgur
Last edited by drafterITA on Sat Mar 11, 2017 11:34 pm, edited 1 time in total.
Cheers! :D
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Re: Gearbest 3.5 Screen Variant B?

Post by mariovisic » Sat Mar 11, 2017 10:35 pm

Your images don't seem to load, but if it's a recent gearbest purchase than it's likely the same board that I received. It actually works fine with 5V out of the box. Test yours out and see.

If you do want to modify it to skip the regulator (can make it a bit more stable + more efficient with power, not having to change 5V to 5V) then the board has an IC that has "XL1509" written on it, that's the DC converter which takes the input and converts it to 5 volts. Here is the datasheet for that chip => http://www.xlsemi.com/datasheet/XL1509%20datasheet.pdf

You essentially want to put your 5v into the output of that chip, which is the 2nd pin from the small divet in that chip. Essentially bypassing the chip alltogether. Hope that helps :)

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Re: Gearbest 3.5 Screen Variant B?

Post by drafterITA » Sat Mar 11, 2017 11:38 pm

Hello! Thanks for the reply :)
mariovisic wrote:Your images don't seem to load
I fixed that.. I think, uploaded on imgur
mariovisic wrote:You essentially want to put your 5v into the output of that chip, which is the 2nd pin from the small divet in that chip. Essentially bypassing the chip alltogether. Hope that helps :)
I'll check the chip with a magnifying lens for the name and attempt the bypass :)
Thank you very much!
Cheers! :D
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Re: Gearbest 3.5 Screen Variant B?

Post by mariovisic » Sat Mar 11, 2017 11:57 pm

That's the one, i've attached a photo of where you should put your 5v in. Although like I mentioned before the screen did work fine for me without the modification, so try that first; I only modded mine to debug an issue which turned out to be something else anyways.

The screen won't turn on without a valid composite signal, so be sure to wire it to the pi's tv pin first before trying this mod.

In my photo you can see that the 2nd and 3rd pins are bridged, that's not on purpose but doesn't matter anyways. You should aim to get 5v to the 2nd pin only if you can :D The 2nd pin is the 2nd one across from the little divet in the chip.

Good luck!
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Re: Gearbest 3.5 Screen Variant B?

Post by drafterITA » Sun Mar 12, 2017 12:20 am

mariovisic wrote:That's the one, i've attached a photo of where you should put your 5v in. Although like I mentioned before the screen did work fine for me without the modification, so try that first
...
Good luck!
Oh well then I'll first try without the modification! :)
As soon as my pi zero and sdcard gets delivered I'll get to it!

Thank you! :)
Cheers! :D
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Re: Gearbest 3.5 Screen Variant B?

Post by drafterITA » Wed Mar 15, 2017 1:38 pm

I finally got to try my screen.. I hooked it to the Pi Zero and it worked straight away.. but I noticed some flickering.. and the text during boot is quite difficult to read, but I guess it's something that you can't really make better.. the resolution is low.
So i proceed to make the bypass.. and after a lot of tries I think I made it.. I was so scared that I messed up the video board.. It took me a lot of tries before I could connect the cable to the chip and then again to the video connector....
I think it's better now, little less flickering..

Now I have to wait for the AIO board from Helder.. I can't do anything else.. the case has been modified as much as possible.. I don't have a screen cover so I can't do that too.. oh well!! Patience! :)
Cheers! :D
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Re: Gearbest 3.5 Screen Variant B?

Post by radusinb » Sat May 20, 2017 7:57 am

drafterITA wrote:
Wed Mar 15, 2017 1:38 pm
I finally got to try my screen.. I hooked it to the Pi Zero and it worked straight away.. but I noticed some flickering.. and the text during boot is quite difficult to read, but I guess it's something that you can't really make better.. the resolution is low.
So i proceed to make the bypass.. and after a lot of tries I think I made it.. I was so scared that I messed up the video board.. It took me a lot of tries before I could connect the cable to the chip and then again to the video connector....
I think it's better now, little less flickering..

Now I have to wait for the AIO board from Helder.. I can't do anything else.. the case has been modified as much as possible.. I don't have a screen cover so I can't do that too.. oh well!! Patience! :)
Could you post a picture on where to connect the video wires? I soldered the wire to the chip but now i can't find a single info on where the video wires need to be :(

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Re: Gearbest 3.5 Screen Variant B?

Post by wario88 » Thu Jul 26, 2018 4:53 am

hi, i use this screen too. all work fine, but I note some flickering too.

at this point i think is a common iusse of this screen. most people have this problem.

Someone has find a fix to the flickering with this screen?

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Re: Gearbest 3.5 Screen Variant B?

Post by GunZi » Fri Jul 27, 2018 8:40 am

I'm using this screen have not encountered any issues whatsoever. There is no modification required. Just make sure you have good solder joints on the pi. I soldered my ground wire next to the TV / yellow wire on the pi.

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Re: Gearbest 3.5 Screen Variant B?

Post by FP2K-Minske » Thu Aug 02, 2018 2:46 pm

Hello everyone!

I was looking at the pcb and wanted to ask some questions.

The capacitors and the coil (near the XL1509) are getting hot... the only connection of the capacitor above is to the "ON/OFF"-Pin (4). And this capacitor connects to the coil below. Is it for stabilizing the current? The capacitor should be collapsing and the coil is for the resistance of the capacitor while being empty (near zero ohm). The capacitor is connected to the VIN-Pin (1) of the XL1509.

Will the capacitors stay cool if I remove the XL1509? I think the 220uF 10V capacitor could be removed too? And the coil below (101) too?

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