[GUIDE] BW Variant 9 modifications

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codeman0624
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[GUIDE] BW Variant 9 modifications

Post by codeman0624 » Tue Aug 15, 2017 11:52 am

During my GBA SPi-Zero build, I had to heavily modify the driver board to get it to fit into the SP shell. I wanted to share my understanding of how the board works, what components can be removed or replaced, and what components I used.

With these modifications you should have:
  1. Fully functional with 5V input
  2. Less than 3mm of overall board height
  3. Understanding of how to use the screen control buttons
This is not a soldering guide on how to remove or replace these components. Though I highly recommend doing this type of work using a hot-air rework station. That being said, how you remove and replace these components is up to you, but you have to deal with whatever repercussions come with your chosen method.

At the end I will include a list of components you can use as replacements.
Expected resultsShow
Comparison of modified and original board. Original on the left, modified on the right:
Image

Showing the profile difference. Much smaller components means you can fit it into tighter areas:
Image

This is the picture I will be referring to in all the following descriptions:
Image


Red Section:
This is an input filter and the bulk capacitance necessary for the input of the step-down voltage converter.
  • Replace D1 with a 1206 size 0 ohm resistor
  • Remove C1
  • Replace L1 with a 1206 size 0 ohm resistor
  • Replace C2 with a 47uF 1206 size capacitor
Yellow Section:
This is the buck converter (step-down regulator) IC, and the output filter components
  • Remove IC1
  • Put a solder blob to short together pins 2 and 3. These pins are shown in the yellow shaded box
  • Replace L2 with a 1206 size 0 ohm resistor
  • Replace C3 with a 47uF 1206 size capacitor
Green Section:
This is a boost converter, that provides a high voltage to the LCD screen. Have not traced exactly what this voltage is for, but it is essential for the screen to work. But it is nice to be able to replace parts and make everything a lower profile
  • Replace L3 with a replacement 22uH inductor
  • Replace D2 with a new flat SMA pacakage diode
Pink Section:
27MHz oscillator that provides a clock to the AMT630A
  • Replace this with a suitable 27MHz crystal
White Section:
This is the 2-pin connector coming from the button board. The pin in the white shaded box is the signal line, the other pin is ground. Yes there is only one signal pin for the 3 different buttons on the board. When a button is pressed on the button board, it connects the bottom side of a resistor on that board to ground, creating a voltage divider that changes the voltage on this signal line. There is an ADC in the AMT630A that converts this voltage and determines what button was pressed. The menu button has a 4.7k resistor, the up button has a 2k resistor, and down has a 1k resistor. With this you should be able to build your own button interface and relocate it wherever you would like. Or find a method to repurpose existing buttons to control the screen, as in my GBA SPi-Zero
  • Remove this connector for the lowest profile
  • Optional: Connect the signal line from your buttons to the pin in the white shaded box, and connect ground to the other pin.

Components List:

Minimum required for 5V operation:
  • Remove IC1 in the yellow box
  • Solder blob pins 2 and 3 (yellow shaded box) to complete the circuit path

Please look at the Expected Results pictures as a reference for what your boards should look like when they are finished.

I will do my best to answer any questions anyone has. But as of right now I am only familiar with the BW Variant 9 board
Last edited by codeman0624 on Mon Apr 23, 2018 7:13 am, edited 1 time in total.

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redled
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Re: [GUIDE] BW Variant 9 modifications

Post by redled » Tue Sep 12, 2017 6:27 am

Incredible guide, very detailed and specific! :D

Thank you for taking the time to write this, I learned a lot for my upcoming Gameboy Advanced SP project.

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32teeth
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Re: [GUIDE] BW Variant 9 modifications

Post by 32teeth » Wed Jun 06, 2018 12:40 pm

Amazing!
If i can make a recommendation. Replace the Tantalum Caps, with Tantalum Caps... ...that way you get no reverse circuit nonsense... ...just in case
and a larger footprint null resistor
Don't forget to check out my other project
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codeman0624
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Re: [GUIDE] BW Variant 9 modifications

Post by codeman0624 » Wed Jun 06, 2018 1:04 pm

32teeth wrote:
Wed Jun 06, 2018 12:40 pm


Amazing!
If i can make a recommendation. Replace the Tantalum Caps, with Tantalum Caps... ...that way you get no reverse circuit nonsense... ...just in case
I don't think there are any Tantalum capacitors on the board I was working with, they should all be electrolytic.

I'm not sure what you mean by reverse circuit nonsense? Ceramic capacitors are nice because they are not polarized, where Tantalum caps are polarized and tend to have a bad (short circuit, thermal runaway) failure mechanism if you install them backwards.

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Re: [GUIDE] BW Variant 9 modifications

Post by Tinkerman92 » Sun Jun 17, 2018 4:19 am

My board goes immediately to 3.3v after going through the buck, I have also confirmed that if I connect 3.3v to the test spot the screen will power up. Do you think I could trim out the buck entirely, replace the components in yellow with the components you listed, blue would be my 3.3v and ground input, pink would be my composite 1 and 2 input.
PCB currentlyShow
Image
PCB trimmedShow
Image

codeman0624
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Re: [GUIDE] BW Variant 9 modifications

Post by codeman0624 » Mon Jun 18, 2018 5:16 am

Tinkerman92 wrote:
Sun Jun 17, 2018 4:19 am
My board goes immediately to 3.3v after going through the buck, I have also confirmed that if I connect 3.3v to the test spot the screen will power up. Do you think I could trim out the buck entirely, replace the components in yellow with the components you listed, blue would be my 3.3v and ground input, pink would be my composite 1 and 2 input.
You can definitely replace the 27MHz oscillator with the one I listed. The inductor you have highlights is 10uH though, the replacement one I list is 22uH. So you'll have to find a 10uH inductor that fits the physical footprint and height you're looking for:
https://www.mouser.com/Passive-Componen ... ?P=1z0wric

It sounds like you've confirmed everything will work with just 3.3V, but I can't really confirm that. Your best bet is to just one-by-one remove components you think are not necessary, and confirm everything still works.

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