Judging by the symptoms, it does sound like a power supply issue. Are all 3 leds on the power board lit? If not, you could have a blown fuse (best checked with a multimeter). If the leds are all lit, you'll need a multimeter to measure voltages

Orange = -5V
Grey/yellow = +12V
Grey/green = -12V
Grey/white = +12V
Grey = +5V

I'd verify all of that first and see what you find out

I'm in the process of converting an old cab to an Arch Rivals and realize this game requires a 49-way joystick. I also realize there are 2 flavors of these joysticks - Williams and Midway/Atari/Happ. Seeing that I found the Midway/Atari/Happ type for a great price, I was wondering if anyone has had any success using these on older Willaims games?