Yup, the screen's inverted, although the screen was dimming before i added the resistor so there was definetely a reversal in performance somewhere.

This may be unrelated, but the backlight color is orange. I was messing around with leds and an arduino, using them as diodes and indicators of sound output in a project i'm working on, and i noticed that red leds have MUCH less resistance than the yellow and blue ones I had. Blue in particular really reduced the volume of the output, while red didn't reduce volume at all.

this may be why my backlight was so demanding, even though it came pre installed with a resistor.

Not just that, but all the games that weren't working before are now WORKING PERFECTLY! I didn't even have to blow on the cartridges or anything! 220R added to a backlight, and what a difference!

Back! Everything's working fine now, and when I play music on LSDJ, the brightness/contrast goes UP instead of DOWN for some reason. A bonus, I guess. That little resistor did the trick!

Heating up the iron as I type. Thanks!

Will update with outcome in a bit!

It's from 1990, if I recall correctly. (it's what was printed on the back of the LCD board). I had been noticing that a corner of the gameboy was warmer than other parts, but it was subtle enough that I always assumed it was just the warmth from the palm of my hand. (the pointed bottom corner, opposite the speaker.) My other dmg is '91, so i could just unsolder the prosound cables from this one and move the whole front screen -cover and all- and stick it on the base of the 'newer' one. Switch halves, basically. Would a year's difference matter?

As for the backlight, I'm using nonfinite's v5 backlight. There's no tutorial at present for that model, but it seemed straightforward enough to install.
I'll try for a resistor as you suggest. I have 220, 1k, and 10k. The page for the v5 says the resistor is already installed though.

That's where they're connected. To the power source directly below the screen  (the leg of what I assume is the capacitor you're referencing), and the ground directly to the right of the screen. The two cables basically reaching for the nearest spots possible from under the cable that sends the vertical data to the lcd.

Hmn. I always assumed that the only regulated source was from that one point on the left of the main board. opposite side from the prosound connection points. Heh, shows how much I know!

That's what I was thinking, but It still wouldn't explain why the dmg can only load certain carts and not others. My reasoning is if there's a problem there, then it most likely extends to all other carts but in different degrees. e.g. Tetris works fine, but that may be because it's such a simple game. LSDJ works (mostly) because the cart is made more robust than the original commercial ones (?). I'm thinking that the backlight draws power from the unregulated source and causes a large enough change in current to 'confuse' the processor and the program, throwing it out of sync and crashing it. (I'm going out on a limb there, I don't know much about how the internals work).

And as is the case for the LSDJ program, all that is needed (as you suggest) is just new batteries so the current remains steady. I just doubt that the other carts will have such an easy resolution.

EDIT: I guess my phrasing was a bit off in my first post; my 'vanilla' dmg is my unmodded dmg which i tested the carts on and they work fine. I also tested LSDJ on it and there were no more glitches, so I'm sure that it's a hardware issue rather than a software one. (also thoroughly scrubbed the connectors, so that's been explored too.)

I pro-sounded and backlit my DMG, and has been working fine(ish) until recently. There's been some wavering of lcd contrast/led brightness since the beginning (not a regulated power source. Looked that up, found it out.), but now LSDJ is crashing whenever anything processor intensive is going on. (e.g. editing tables during playback, editing chains during playback).
Not only this, but for some reason my backlit DMG can only load the LSDJ cart (EMS) and some of the 'older' games I have. Such as tetris, yoshi, and pac-man. Anything like Link's awakening or pokemon gold/silver just stays in a bootloop.
The carts definetely work, as I have a vanilla DMG which plays them just fine.

Long story short, does the LCD being wired to an unregulated power source have any correlation with game crashing? I need to know before I do any rewiring, as the cables will have to be lengthened and insulated and stuff.

It may be fixable if I just replace the batteries before they get low (as I'm suspecting atm), but that's not a REAL fix.

Anyone know anything about this?

Sup! I made this GH/RB guitar full MIDI mod, link to the github page enclosed,
I made this guide as simple as I could, but I'm assuming you have a basic grasp of, well, arduino stuff really. And soldering, and how to find the ground and power on a chip.

I'll add more info to this post as I go, so consider this thread a WIP. (Program's stable and working though, the download's on my github page)

The aim of my project was to make a standalone MIDI controller with the musical capabilities of a full instrument, but still play like the video game.
Basically THIS, but with sound.

It's an arduino mod that intercepts the button presses directly, without dealing with the controller's chip and its platform-specific protocols.
As a result, this setup is universal for all the GH and RB guitar models. Secondary frets from the RB guitar is on my todo list.
Also, if you already have the controller, the basic setup just requires an arduino, and nothing else! (Obviously, you can add a midi port, but this can work though usb too)
In theory, all modded instruments should be able to stay backwards compatible with the game.

You'll be happy to know that the default octave range I've preset keeps within the DMG's limits!

Scaling up on the frets is represented here. Check the tabs below to see the setup more clearly with octaves and notes written in.
This table is just here to look pretty :)
#  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #
#  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #
#  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #
#  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #
#  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #  |  #

You should be able to see a pattern in this. It's designed so you shouldn't need to do too much work around the base octave.
I recommend hanging around the 3 finger combinations. easy drops to bass, and wiggling your middle finger gives a nice hammer-on combo.
The progression of notes is pretty logical. I have an in-depth guide below. It's lengthy, but it's the most comprehensive description I can give on the system. The theory actually gives you shortcuts to some cool scale-jumping if you check out the bookcase system!

› Basic operation

› A fret table you can read without getting a headache

› In-depth guide on note progression

› Universal-ish guide to wiring it up

› TODO

The Github page: https://github.com/MagicalGentleman/arduino-hero