Ahh okay. I guess I was hoping there was something I could do to test it and see if it more or less works by applying power to a couple of pins.

I now have three of these devices (4x20 alphanumeric vfd's) ... only one is fully functioning with the serial controller. One of the other serial controllers is permanently fried. But the last one, the controller works, but the VFD doesn't light up. It's like the contrast is down, but these guys don't have a contrast setting, right?

I've tried swapping the good controller onto another VFD, but no different results. While fiddling with a multimeter I managed to somehow get this half-broken display working again, I have no idea how. But when I unplugged it to move it to another location, it reverted to it's original non-display state.

Greg