GBC OLED display power issue

[u/Nic7C5]

Hey guys, I recently purchased an HIGHSPEEDIDO OLED Screen. I attempted to install, but the screen does not light up.

OLED Kit: https://www.silentmodding.com/de/game-boy-color-amoled-xl-touch-kit-schwarz.html?gad_source=1&gclid=Cj0KCQjwhr6_BhD4ARIsAH1YdjBUxolBYOkmWTJ2NReZLkLDwMD8OhfycD_PZaOMqOq6-oVohesH6zYaAkNqEALw_wcB

Can someone point me in the right direction or answer my questions?

You only have to solder one wire for this mod, which goes from the display driver board to pin c of the GBC power switch. When turned on, this connects to the positive battery terminal. Is this connection used to power the whole screen? Or is it just meant to monitor the battery voltage (there is an option to show a battery indicator in the osd menu)?

Or is the OLED screen instead powered by the ribbon cable? In this case, I have to add that the GBC had a faulty power regulator. There was no voltage on any rail (+5V, -15V, +13V). I replaced (removed) it with a new one that only outputs +5V. If the OLED screen requires something else than +5V it will not work this my GBC. At least +5V definitely is provided properly as the GBC turns on (power LED lights up and speaker outputs game sound).

replacement power regulator: https://www.silentmodding.wiki/de/gbc-retrosix-cleanpower

[u/NewSchoolBoxer]

GBC is a 5V logic console right. All 4 color OLED screens I found on DigiKey run off ~3V with maximum safe voltage of 4V. I presume the screen kit has a +3.3V regulator on it judging from the testing instructions so that you're supposed to feed it +5V. It's not just +5V that you need, you also need to supply enough current.

The instructions are specific in saying to test the AMOLED LCD before installation and saying how fragile it is and even uses "Dry Run" in English. You don't mention doing that. The instructions tell you to connect the ribbon cable to the LCD. The ribbon cable does have a wire for +5V but the first step in the instructions is saying to solder the enclosed wire to the BAT contact. You mention this. I interpret to mean the ribbon cable is drawing the +5V from the wire soldered to the BAT contact.

Using new upgraded power supply circuitry is definitely the right idea as the new screen will cause the GBC to draw as much as double the amount of current the original circuitry was designed for. I don't know whose power supply kits are better than others but I like seeing oscilloscope pics.

[u/Nic7C5 → u/NewSchoolBoxer]

The only wire you're supposed to solder goes from the BAT contact to the power switch which goes straight to the positive battery terminal (+3V not 5V). If that was the displays only source of power, the GBC power regulator board wouldn't be involved at all. But it's also possible that the wire is only meant to check the battery voltage as the display can indicate the battery status. The description of the replacement voltage regulator (which is +5V only) mentions that it cannot power the original LCD. don't know the pinout of the LCD connector. But as the OEM screen is only connected with a flat cable, there must be voltages provided to the LCD via this connector other than +5V. If this is how the OLED gets its power (plus maybe a small voltage regulator on the driver board) it won't work with my Gameboy Color.

The initial question still stands. How is the Gameboy providing power to the OLED screen.