Vintage Help 3DFX 5500

I'll cut to the chase I got an 3D issue that cuases the screen to turn blank like it was on standby mode when starting games or fraps. I replaced the orginal fans with new Thermalsheild fans unlike the avvid fans which were filthy. I also replaced one of the heatsinks and cleaned the front gpu to reduce heat with a much better one. The card post with out artifacts and runs normally in 2D mode. I also downloaded and installed the XP drivers for this card. To rule out the psu I replaced it with a spare 500w unit that I had on hand. The retro box is a compaq 5400us with a upgraded p3 1.4ghz 133fsb. So pls any suggestions to get passed this issue will test card in a win 98 box to rule out the card its self. My other vintage agp cards worked with out any issue even when running fraps, 3dfx 3500 and a geforce 256 64mb.