I have an Apple iMac G3 333MHz, Bondi blue tray loading. The CD-ROM stopped reading discs years ago, and even with a 128MB RAM upgrade it's really too slow to do anything interesting with (I have zero nostalgia for MacOS 7/8/9 era gaming, and MacOSX 10.3 on a single core 333MHz does not browse the Internet well). Plan is to turn it into a RPi4 + DOSBox + box86 + WINE retro gaming machine. The form factor is nice, as it's an all-in-one with a 15" CRT and a big handle on the top, making it a somewhat "portable" CRT gaming machine. The 15" CRT on this thing is beautiful, and despite a very limited choice video modes, displays an amazing and sharp picture. Later iMac models (slot load models, DV and eMac) require all sorts of custom I2C commands to fire up the CRT. *Apparently* this one does not. I've had this project on the backburner for eons, and after a few parts finally turning up from China, I'm giving it a go. First up, converting a DE15 VGA connector to DB15 RGB. After a lot of butchering of cables that never worked properly, I grabbed some of these screw terminal break out connectors to allow me to do a bit of trial and error (ironically then getting it working the first go). Plugging that into the iMac with the "logic board" (Apple speak for the motherboard, including the custom ATX power supply and audio front panel headers, as well as the power button connector), I've got the DB15 removed from that and plugged into my custom cable: Powering on the logic board and then feeding the strict 1024x768@75Hz mode, I get a picture. Woo! But here's where the fun ends. If I remove the logic board, I can power on the system by shorting pins 23 and 24 on the custom ATX cable. For this iMac family, +5V needs to go from the standby voltage pin (24) to the power on pin (23). I've connected that with a 510 ohm resistor just to be safe (most guides online say 200-400ohm). That gets the system fan spinning, and the power on light changes from off to "standby" orange. Again, I send my 1024x768@75Hz signal, and three things happen: 1) The fan spins faster 2) The orange standby light turns to green 3) The degausse coil cycles on and off But no picture! Bummer. Kind of stuck now, as this isn't very well documented. Later models with I2C control have lots of work documented, and lots of other people just tear the CRT out and put in an LCD (sacrilege!) I've posted on the MacRumors forums where some clever folks hang out, asking there. But looks like the rest of my weekend is going to Googling about, hoping someone somewhere knows what the magic sauce is. I'm hoping it's something trivial like "you need load on one of the pins" or something. If it actually does need I2C commands to do things like set the initialisation brightness, then I'll attempt to do that via the RPi's GPIO pins into my screw-terminal connector (from what I can tell, these monitors take I2C off a couple of spare pins on the DB15 connector).