Help modding board to run with 5V

[Luis Mendonça]

Hi everyone! I recently got this new 7 inches screen, and right out of the box I tried running it with 5 v before modding. It did run, but the screen quality was lower than it was when running with 12V, very noticeable (Using a variable power supply helps a lot when testing these) and all the controls buttons from the screen were not working when using 5v (Power, menu, up and down, etc) just the contrast button was ´partially working but on the video selection button instead of it's right button.

I mapped some of it's voltage points but it's a tad confusing to me where I should inject 5v or what I should remove, because I'm getting some crazy readings here... (All tested with 12V supplied)

In order as I labelled them.:

1 - MP 1482 https://www.monolithicpower.com/pub/media/document/MP1482_r1.31.pdf
As the file says "The MP1482 is a monolithic synchronous buck regulator."
On point 3, as marked, it's output is + 5V

2 - PT4103 http://www.micro-bridge.com/data/CRpowtech/PT4103E.pdf
It says there "The PT4103 is a step-up DC/DC converter", I hope I got the right datasheet here, but it checks out, on pin one the output is + 5V as well.

3 - 662K voltage regulator (Didn't find this specific datasheet)
Yellow pin = +5V,
Red pin = +3.3v

(What I did find is that these 662K are 3.3v regulators so this checks out,
nothing to do here)

4 - LD3 (N? or Z? couldn't find anything about this one, nothing but a seller on aliexpress, with no description for it, but my guess it's also a voltage regulator?)

Yellow pin = + 9.3V
Blue pin: = + 5V
Red Pin: = + 14V


5- LD3 (N? or Z?)

Yellow pin = - 5 V
Red pin = - 8,5V

(Yup, they are negative)

So, should I just input 5v to that first IC's output? Tried that, did not work.

 

[The hob]

You can ask the aliexpress seller about LD3

 

[tzmwx]

Look at the picture

 

[Luis Mendonça]

You can ask the aliexpress seller about LD3

I did, he/she didn't really know what it was about, now I can only find it in alibaba.

Look at the picture

Which pin are you jumping there? It's to solder +5V input directly to that rightmost pin of this drum inductor?

EDIT: It's working as of tzmwx post, the buttons from the original board still do not work as expected, that may be because of resistance, but I haven't yet checked it, and at 8V the board works perfectly. For a ps2 portable project I'm undergoing, it's going to be perfect to work at around 6-8.4V.

Thanks!