Its funny you mention that, a few hours ago I had already begun the process of interchanging the bottom board hopefully to find a fully functional CPU.
I then put in the flashed cart as you mentioned and to my surprise you were absolutely correct! The problem lied in the bottom PCB CPU unit, not the top PCB ribbon cable which I had presumed.
The 'Left-test.gb' ROM works beautifully for LEFT & B button diagnostic purposes.
nitro2k01 you might want to inform future testers that it is intended for screen to freeze at the 'NINTENDOr' logo after the ping, until either LEFT or B button is somewhat function and activated. I didn't quite know really what to expect and was considering that I may have done a bad flash or it was a cart related problem.
Although my inverted polarization screen actually turned white, which kinda threw me off for a few minutes.
FUNCTIONALITY!
1 Gameboy down, 2 more to go wish me luck!
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On a side note:
Does anyone know where I could locate a tutorial / inform myself on how I "should" go about painting a DMG01?
What type of paints works best for a matte finish, while still withstanding minor scratches and such or how to add a protective sealant layer.
Spray paint, acrylic paint, paint markers???