You should be able to zap the PRAM by holding down the key combination either before or after the start up chime. I've read, but am unceratin, that zapping it before the chime actually resets more parameters. Pulling the battery and pressing the CUDA switch should reset everything that is stored in NVRAM/PRAM memory.
For that matter, you could just try pressing the CUDA switch, IIRC, near the back corner of the board near the third PCI slot.
In cases like this, I recommend you remove the PCI video card, leave in the personality card, you need that, but remove the modem card from it, remove all the RAM but one stick, unplug all the hard drive cables, SCSI and IDE. Don't plug in a keyboard or mouse. Remove the battery. With machine unplugged, hold down the CUDA button for 30 seconds. Leave the battery out. The Beige doesn't need it to boot.
Connect a known working monitor which is capable of 640 X 480 @ 67Hz to the built-in video. Power up with the power button on the front (back? can't remember). If you get a good start up bong, wait a couple of minutes to see if the monitor becomes active. If not, try a different memory module.
If you can't get a good start up bong or video on the monitor, the problem must be on the motherboard or the monitor. It's unlikely, though possible, all three memory modules are bad.
If you do get a good start-up screen (gray screen with disk icon and flashing ? mark) start adding components back. Start with a mouse. Then keyboard and mouse, etc.
All that said, here's another possibility... The bus speed and CPU multiplier and cache ratio are controlled by a set of jumpers on the motherboard. Are those still in their original position? Does the machine still have the original CPU module installed? Also, you may wish to check the heat sink grease between the CPU and heat sink. If it's turned to powder, you could have a simple case of the CPU overheating soon after power on.