40 pin GBA with white tab LCD perfect solution!

Discussion in 'GBA - Hardware, Devices and Utilities' started by malheur, Nov 13, 2016.

  1. malheur
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    malheur Member

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    i finally found "A PERFECT" solution for 40 pin GBA with white tab LCD(type B).

    physically and theoretically prooved.

    so i proudly present the way those fix. very long story.

    when you mod backlight screen to original GBA, especially 40 pin old revision, you will have "WASHED OUT" problem. all the color fade out very white.

    like this :

    1_washedout.jpg

    so you've been told solder some pins, like REVC + GND, REVC + VCOM + GND, V2 + P2-VEE or anything else. then brightness will be normal, but it will eventually having "GHOSTING" problem. aka IMAGE RETENTION or IMAGE STICKING. last image sticking after a while and smear vertical line in high contrast.

    like this :

    2_ghosting.JPG

    even some people tells it's normal when you use backlight screen on GBA. no no.

    so i read like 10 about general TFT-LCD white paper for just fix this problem, which wroten by English. eventhough it's not my mother tongue and i'm not even engineer or educated, but i did.

    little explain for causes those issues from what i learn :

    LCD shows graphics on what they called "common voltage". REVC, COM, VCOM is the kinds of common voltage yet slightly different each others. REVC is the original signal generated from processor, COM and VCOM is generated from REVC signal with some circuitry.

    GBA SP backlight LCD require REVC and COM signal, but original GBA send P2-Vee and VCOM signal on those road, so voltage doesn't matchs. too low(minus voltage). so every other signal affects too high voltage compare to common voltage. that's why its washed out. and if you forced solder REVC to GND, common voltage will be "up" to "zero(i mean 0V. GND)", other signal voltage will be "relatively" normal and graphics grayscale will be fine.

    then again, TFT-LCD shows graphics by charging and discharging the pixel cells. but if always charging, there will be capacitor effect in cells, and left image retention. so when you forced REVC to GND, other signal doesn't back and force like -10 ~ +10 volt, always 0 ~ +20 volt. image retention!

    anyway, let's fix.

    ---

    1. preparation :
    soldering iron
    solder
    thin wire
    sharp knife
    IMPORTANT!! - SMALL SIZE POTENTIOMETER

    ---

    2. cut the ribbon :

    3_ribbon.JPG

    as you can see, there is "C1" and "C2" on the ribbon. cut it. but not the exposed metal part. if you cut at exposed metal part like me, it will peel off metal layer on vinyl layer when you solder. so i did my mistake, have to solder from LCD connector side. please don't do that. cut at near GBA side for keep solder point firm.

    Untitled-1.png

    and also when you use the knife, cut left and right like chop it. don't slice. slice may damage next line.

    if you use the ribbon same as me, inner 2 wires are the C1 and C2.

    if you don't, C1 is 27th leg of LCD side(30th of GBA side) and C2 is 30th leg of LCD side(29th of GBA side). track down these pins and cut them.

    what are those? C1 is REVC of LCD needs, but GBA send P2-Vee signal. C2 is COM of LCD needs, but GBA send VCOM signal. two of those signal doesn't match. i guess the maker of this ribbon cable aware that and left some points for future-proof. so we should supply those signal from others.

    ---

    3. wiring C1 :

    REVC does exist on the GBA CPU but it's just doesn't sending on cable port. you can easily find REVC on the board. wiring C1 to REVC.

    4_c1.jpg

    so far it's easy enough.

    ---

    4. wiring C2 :

    C2 is more tricky. since there is no COM signal on the board, you have to make them. the white paper said theoretically COM is exact middle point of voltage runs LCD. our LCD runs 3.3V, so it will be near 1.65V something like that. but the white paper also said every product has slight difference, so normally it's adjustable from potentiometer. ring a bell? that's why GBA also have potentiometer.

    but it's connected VCOM signal which we just cutted off because it's useless. so it's doesn't work anymore and we shouldn't use that. we need another potentiometer.

    5_pot.jpg

    i used a one which i don't remember how i get, but anyway you need to find or buy one. i recommend small size one. i used relatively big size one, so it was hard to fit into the case.

    just fyi, what i used is "Bourns 3386PT 500k Ohm". but any potentiometer over 100k Ohm would work. and again, use smaller one.

    there will be 3 leg on the potentiometer. usually #1 to +Volt, #2 to using, #3 to GND. so #3 should be GND and #2 should be C2, but wheres +Volt?

    6_c2.jpg

    there it is. it's regulated 3.3V. CP3 capacitor + point.

    ---

    5. testing :

    turn on while the GBA housing still opened. you can't put the batteries while rear housing open, so use clip or wire for power supply.

    you can see ghosting was compleletly gone, but there should be shown interlace lines (and slightly low saturation).

    7_interlace.JPG

    adjust the potentiometer we put in and it's all gone! PERFECT!

    move your character up and down while play any RPG will be good to see and adjust interlace line on your bear eyes.

    when you done, assemble the full housing.

    8_done.jpg

    you can see through the additional potentiometer i add on rear side.

    ---

    conclusion :

    - cut C1 and C2
    - wire C1 to REVC
    - wire C2 to generated voltage from additional pot
    - adjust the additional pot



    ---

    sources :
    pinout - http://problemkaputt.de/gbatek.htm
    basic TFT-LCD - http://www.densitron.com/media/docs/White_Paper_on_TFT_Technology.pdf
     
    Last edited by malheur, Nov 15, 2016
    VinsCool, YuseiFD, zfreeman and 19 others like this.


  2. Virdoo

    Virdoo GBAtemp Advanced Fan

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    Awesome job. Without potentiometer is not possible to solve ghost image?
     
  3. WiiUBricker

    WiiUBricker Insert Custom Title

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    Do those GBA backlit mods sold on ebay have real AGS-101 screens or clones? Is it possible to get a pre-built GBA with a properly calibrated AGS-101 screen for a decent price?
     
  4. malheur
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    malheur Member

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    yes. only potentiometer can supply precise voltage. otherwise, there will be left little interlace.

    however if you have enough soldering skill, you can actually detach the original potentiometer and possible to reuse, but it's effortless.

    when i want to fix my problem, i even read and study white papers about TFT-LCD and it was dozens of pages. i checked the voltage of every single point of GBA board, solder so many points, and your question is this? google it dude.
     
  5. WiiUBricker

    WiiUBricker Insert Custom Title

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    No offense man. The question wasn't directed at you. You did an awesome job with your mod. It was directed to the public and since I'm too lazy to create a thread, I chose to use your thread. Goolge won't help though because other people don't include the information about the potentiometer and LCD and stuff, so I would have probably end up with a GBA and a poorly calibrated screen.
     
  6. malheur
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    malheur Member

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    ok. there is 2 kinds of GBA original. 40 pin version(earlier) and 32 pin version(later). also there is 2 kinds of backlight LCD. brown tab(earlier, 3rd party made, known "A" or "AB" type) and white tab(later, Nintendo original OEM, known "B" type). the known combination with no issues is :

    40 pin with brown tab
    32 pin with white tab

    opposite way makes issues. so it's easy if you possible just choose each part. but the problem is, brown tab LCD seems no longer produced. also there is plenty of 40 pin GBA but hard to find 32 pin GBA. at least in Asia countries. so when you bought already-modded one, it will probably 40+white combination. seller usually doesn't specify which one is it. no matter what, in this situation eventually people will have opposite combination and want to fix the issues and use it.

    i also somehow got 40 pin with white tab, so searched a lot data about 40 + white tab combination even in many language, but none of them found a way. then i approach start learn the basic signal protocol of TFT-LCD and found myself a way to fix. that's maybe a reason they don't talked about pot stuff. because it's not a known way. so until now, you must use 32 pin GBA for perfect graphics.

    another reason you never tell is, both user and seller doesn't care about a little graphical false. ghosting? who cares. that's the way it is.

    so if you want to buy already-modded one, check it's 32 pin. you CAN google how to tell 40/32 pins. probably seller doesn't want to tell which one is, then assume it's 40 pin.
     
  7. WiiUBricker

    WiiUBricker Insert Custom Title

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    Thanks. I will get one and refer to your information here if I need to fix the screen.
     
  8. Virdoo

    Virdoo GBAtemp Advanced Fan

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    I'm using 40 pin with white tab and still getting ghosting image. Anyway, will you make maybe video tutorial about it? It would help a lot.

    I didn't understand very well part with cutting off 2 wires. So I need to cut off 2 of 4 wires on circled part? C1 and C2 wires.
     

    Attached Files:

    Last edited by Virdoo, Nov 13, 2016
  9. slaphappygamer

    slaphappygamer GBAtemp Maniac

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    I will probably be selling one soon.
     
  10. malheur
    OP

    malheur Member

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    yes. inner 2 wires are C1 and C2. cut those with sharp knife.
     
  11. Le_Gogh

    Le_Gogh Member

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    That's some amazing work malheur, wow! I'm tempted to try this myself, but my soldering skills aren't the best. Any chance you could post some images of the solder points on the actual ribbon adapter? I think if I'm going to make a mistake it will be there!
     
  12. malheur
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    malheur Member

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    solder points of ribbon cable IS "C1" and "C2". mine was broken since i was try too many tests and cut the metal part, so i had to soldered alternatively, but "C1" and "C2" is the metal point that can be soldered on the ribbon. that's why you should cut the LINE of C1 and C2, instead the metal point.

    i will change the picture for not making misleading when i get a new ribbon cable in a few days.
     
  13. Syed

    Syed Newbie

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    Great work, I did one but I boosted the brightness by running a wire from P1 on the adapter cable to DA1 leg.
     
  14. gaggi

    gaggi Newbie

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    Great work and a big thank you @malheur
    Did this mod Yesterday and it fixed my problems.
    I actually used the poti which was already on the GBA motherboard, i got rid of R15 next to it and soldered the 3,3v from the capacitor to the top solder pad of R15, then disconnected the top leg from the PCB, soldered it to C2 on the adapter and insulated the bottom of the poti with some electrical tape, works like a charm.

    Anyway i think you could simplify this mod by just connecting REVC to P2-VEE on the CPU side of the GBA Motherboard and remove R16, R17, C33, C54 and Q3 on the other side.
    The removal of R16, R17 and C33 would disconnect the P2-VEE on the ribbon connector from the rest of the circuitboard and getting rid of C54 and Q3 would send the unaltered output of the original poti directly to VCOM on the ribbon connector.
    No need to get a new poti or cut the ribbon cable this way.

    Im not sure which voltage goes out of R15 and into the poti by default, so maybe it would be necessary to unsolder R15 and connecting the 3,3V from the capacitor below to the top solder point of R15 as well.

    I am to lazy to try it out with the GBA i just modded (since its an Christmas present for my brother in law, which is already wrapped) and have no other flying around so it would be nice if someone could test this out.
     
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  15. malheur
    OP

    malheur Member

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    that's nice you've done this mod. and thank you for sharing exact desoldering point.

    i was also thought it's possible to directly mod with cable pinout swap of gba mother board, but somehow i prefer preserve the original mother board as best as i can. but now i think it's easier just desoldering.
     
  16. gaggi

    gaggi Newbie

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    I've got an positive reply from a guy on another forum who just did the mod with just removing the listed parts. https://circuit-board.de/forum/inde...Mod-AGS-101-Display/?postID=593578#post593578

    I can understand anyone who want to change as little as possible on the original Hardware, i just wanted to share this method because in my opinion its much easier and you don't need any extra parts (except for an tiny piece of cable).
    ... also "once you go 101 you never go back" ;)
     
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  17. skaman

    skaman Member

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    I modified two 40 pin GBAs with the AliExpress white tab LCDs.

    One motherboard had no problems with the LCD. I did the standard P2-VEE + GND mod and the display was bright with no interlacing and almost imperceptible ghosting.

    The second motherboard had nothing but problems with the LCD. I started out with the P2-VEE + GND mod which was terrible. I moved on to malheur's REVC + GND / V2 + P2-VEE and that was a big improvement. I still had slight ghosting and some flickering (on GB carts) so I was searching for a solution which I found in this thread.

    I performed gaggi's component removal on the second motherboard and it was a success! Absolutely no ghosting or interlacing. There is still a faint flicker using a GB cart but that might be because I didn't connect the P1 on the ribbon cable.

    Now that I've successfully performed gaggi's mod on the problem motherboard, I did a side-by-side comparison with the first motherboard and its faint ghosting really stands out. I guess I'll have to convert the first motherboard, too.

    UPDATE: Made the P1 to DA1 connection and my GB cart flickering is gone. Display is now PERFECT!

    BIG THANKS to malheur and gaggi!
     
    Last edited by skaman, Dec 18, 2016
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  18. Hovel

    Hovel Newbie

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    Malheur, thank you so much for this tutorial!

    I'm new to the gameboy modding world, but this really helped me with my first mod. Even soldering (on this scale) is new to me, but it really only took me 3 hours to install everything; screen, ribon cable and all the soldering.

    Maybe you can use some of my pictures in your OP, since some people have asked for it. Use them anyway you like:

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
  19. UAC_Pilot_One

    UAC_Pilot_One Newbie

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    @malheur
    Hi there, just signed in at this board to give you a big up for research and developing this mod. :bow:

    Unfortunitly I decided to do the backlit mod to my 40pin GBA a few days ago, so your work just had perfect timing. As I have to wait for the display, I cant tell anything yet but will give you some feedback here. I did ordered at aliexpress a 40 pin ribbon adapter , the display and a glas lense. Can you please confirm that you used the same ribbon cable and display as I ordered?!

    Anyway, I decided to put in a potentiometer to not unsolder all the other elements. Trough a small hole it is possible to do the allignment, as it was on the original as well.

    P1020350.JPG
    P1020351.JPG
    P1020352.JPG
     
    Last edited by UAC_Pilot_One, Jan 10, 2017
  20. nakedfang

    nakedfang Newbie

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    Hello all,

    Great job, thank to malheur and gaggi. I'm using the two methods, it's work perfectly for me. :sp:
     
    Last edited by nakedfang, Jan 12, 2017