momeedees
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Hi all,

so after years I got back into my DMG collection
and went through my scrap DMGs to test them out and fix.
I got one which had a few dead lines, which were easily fixed, however it
has abother weird problem:
When turning it on, the screen is directly all black.
The contrast wheel doesn‘t change anything
(I think sth. actually changes veeeeeery slightly but all in all it stays black, I also have the impression that after some time, a picture of noise appears, some pixels get almost unnoticable brighter).
The cables seem fine, sound works.
I changed the potentiometer, but nothing changed.
I connected another LCD board, which worked fine.

I found this post from a few years back, but it doesn‘t seem to be solved: https://chipmusic.org/forums/topic/1593 … -contrast/

Has anyone encountered this issue and solved it?
I got a soldering iron, multimeter, a bunch of caps and the will to try and fix it, but I really do not know what to do hmm
Any help appreciated!

Apeshit
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Was the DMG modded? I've seen this occur often when people disassemble DMGs or backlight them. There's an adhesive piece that holds the LCD to the plastic shell, usually it's dried up by now and doesn't cause issues. But sometimes when removing the front PCB, the LCD hangs onto the shell and the *soldered* connections on the brown ribbon cable, underneath the LCD, get torn. This causes a physical tear that can not be fixed, but can sometimes be remedied with solder.

Not sure if that's your issue, but I'd suggest gently lifting the LCD and inspecting those connections. Or apply gentle pressure to the connections while the gameboy is running and see if you see the LCD flicker on.

momeedees
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Thanks for your reply apeshit.

I would assume the connections on the brown ribbon are alright.
As i turned on, all was black woth a few white/empty vertical lines.
I carefully removed the black sponge and adhesive film, and fixed the vertical lines by heating a small flat screwdriver with my soldering iron while rubbing the brown tape at the esge of the glass. All white lines turned black (had approx. 5 lines on the left side and around 8 on the right side of the screen).
If the brown tap is damaged, shouldn‘t I have had no lines at all?

Its an unmodded device, the adhesive that sticks screen to shell was still there as well and sticky.

Apeshit
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If the brown cable is damaged, you will have no lines at all, yes.

edit: As in, you will have no readable lines.

Last edited by Apeshit (Apr 1, 2018 4:11 pm)

momeedees
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Mh, Is there any way to verify/falsify (measure sth. With the multimeter, visual indicators) this kind of damage? Sth to look for?
Can you also tell me about the remedy you wrote about?

edit:
applying pressure (brown ribbon), gently wiggling around (white ribbon) brings not change at all, not even slight hints.

Last edited by momeedees (Apr 1, 2018 6:25 pm)

momeedees
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Some pictures...
Close up of the "noise" I mentioned earlier, note that this is static and not moving or sth.
This appears in a smooth manner (takes like 2-3 seconds) after turning the contrast wheel all the way down.
Turning the wheel all the way up, makes the noise disappear and the screen shows evenly black.

The rear side of the LCD Board. I replaced 3 caps (C1, C2, C3) with caps from a scrape board, as well as the contrast wheel, assuming it would help, but nothing changed. The screen shows the same behavior when C3 is not soldered in at all (I wanted to see a changed behavior if a cap is missing).
The Jumper J2 had some corrosion form this side of the board, close to the left hole, you can still see some. I cleaned it with vinegar essence as good
as I could.

momeedees
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So some suggested to resolver the ground clips and bend them a bit.
I saw a YouTube Video on this, the guy in the video however just bend the clips and pressed the LCD board on to the power board, I had tried and failed with that initially.
BUT!
After the suggestion I thought to give it a try: Removing that mucky solder and reapplying fresh one did the trick! The screen works!

Even though working, its rather faint and flickers. I resoldered the connections of the wheel, and freshened up a few other solder blobs that seemed dull, to no avail.
I might try a complete recap those days.
Thanks for the suggestions and I hope some day this info might help someone else smile

Apeshit
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momeedees wrote:

edit:
applying pressure (brown ribbon), gently wiggling around (white ribbon) brings not change at all, not even slight hints.

To clarify, you put pressure on the soldered connections, underneath (not below) the LCD?

edit: I really need to read the thread before replying.

What did you reflow to get this working exactly?

Last edited by Apeshit (Apr 2, 2018 10:28 pm)

StarkNebula
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I'm having similar issues. Many years ago, I was new to soldering and whatnot and got my screen stuck in this state while trying to reconnect a front-light mod. I'm still uncertain how I got it there because the LCD ribbon cable is intact. Out of desperation I bought a capacitor kit which I did about 2 years ago with no success. I recently brought it back out to see what could be done.

I've followed the advice in this thread thus far but it hasn't resolved my issue. I'll list what I've done:

LCD board modifications:
* Installed new capacitor kit (C1, C2, C3, C6, C7, C8, C9, C10)
* Replaced 100 ohm and 1k ohm resistors
* Replaced 47uF capacitor C4 (not part of the kit)
* Transplanted tested-working potentiometer
* Resoldered the grounding contacts

What's not replaced:
* Diode D1
* Capacitor C5
* DA1, DA2, DA3, DA4 (Rectifier diodes if my research is correct)

Way way back I bought a lot of 5 LCD boards that were supposedly dead off eBay. Only 1 was damaged beyond repair so I do have some spare parts I can salvage if that's of help.

Apeshit
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Reiterating on what I said above, this issue is almost always caused by the white ribbon cable that connects the two boards breaking internally (you won't see a physical tear), or the brown ribbon cable under the LCD detaching.

While replacing caps is good practice, it shouldn't be the first step when troubleshooting, since the caps in DMGs are pretty good.

StarkNebula
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I had a look at my LCD ribbon cable again and sure enough 2 pins towards the top had their connections broken. I re-soldered them and check the continuity but still no luck. I have a variety of boards with the same problem though and the others don't show signs of wear near the ribbon cable. I'll try and post some images later. Hopefully there's something I can do; it would be nice to know what to trouble shoot with this issue.

alfonsg00
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StarkNebula wrote:

I had a look at my LCD ribbon cable again and sure enough 2 pins towards the top had their connections broken. I re-soldered them and check the continuity but still no luck. I have a variety of boards with the same problem though and the others don't show signs of wear near the ribbon cable. I'll try and post some images later. Hopefully there's something I can do; it would be nice to know what to trouble shoot with this issue.

I have the same problem, screen black and slight change with contrast wheel, did you guys fix it? Tried everything, removed and reapplied new solder paste and the ground spots. Also went over every solder bit inside, remelted it. Did someone of you fix it? How do i know IF the LCD cable is bad?

Last edited by alfonsg00 (Sep 10, 2019 10:40 pm)

Apeshit
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I recently encountered a DMG in this state, and I replaced the power regulator board from a different DMG and it fixed the issue.

alfonsg00
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Apeshit wrote:

I recently encountered a DMG in this state, and I replaced the power regulator board from a different DMG and it fixed the issue.

Hi!

Where is the power regulator board located? That could not be my issue? I havet tried replacing the whole board with the screen attached from, with an working gameboy screen board and the screen works perfekt then...

Last edited by alfonsg00 (Oct 7, 2019 2:10 pm)

Orgia Mode
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Sea of Souls

This is the power board:
https://gbhwdb.gekkio.fi/static/dmg/GM1 … d_back.jpg

Did you say the LCD "does" or doesn't" work on another gameboy.

Last edited by Orgia Mode (Oct 7, 2019 5:21 pm)

alfonsg00
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Orgia Mode wrote:

This is the power board:
https://gbhwdb.gekkio.fi/static/dmg/GM1 … d_back.jpg

Did you say the LCD "does" or doesn't" work on another gameboy.

I took the lcd board from a working gameboy and plugged it into my faulty unit. And then it worked. So the problem seems to be in the lcd board?

Last edited by alfonsg00 (Oct 7, 2019 10:07 pm)