iMac G3 Hardware mod - video help?

Discussion in 'PowerPC Macs' started by bearsomg, Sep 8, 2012.

  1. macrumors newbie

    Sep 8, 2012

    A while back I bought an iMac G3 slot loading from a thrift sale because it was only $6, worked perfectly, and came with the keyboard and mouse.

    I finally decided that I want to mod it and stick in an Intel mini-ITX board to replace the iMac's logic board, while still using the iMac's CRT as a monitor. I know this is possible because I have seen a few posts about people who have successfully installed Mac Mini hardware in these machines while still using the original CRT.

    So far I have the case completely off, the logic board out, and I pulled off the video board to look and see if I could find the pins I needed to make a VGA adapter. I managed to find a pinmap for the HE20 connector and a VGA cable here:

    Using that pinmap I have wired a VGA cable up to the HE20 video connector under the logic board. Since I read somewhere that the power board needs +5v on the PFW pin to turn on, I bridged it to the T5V pin. When I plug it in and bridge the pins, I can hear the CRT charging up which tells me that the system is powered on, however no video is displayed on the CRT. I am currently using my laptop to test it, with a resolution of 1024x768 at 75Hz, which I know is supported by the monitor because I used that resolution when the PPC logic board was still installed. Does anyone have any ideas? I'm pretty much exactly where this guy ended up:

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