I’ve got a VFD display on board along with UPD16311 driver is made for negative voltage around -30V and i think so is display (i couldn’t find any info on display) and I’m doing it mostly from junk parts. I want to know what devices could/should contain power supply for such voltage. I’ve tried -12V from psu i’ve got lying around but it didn’t work. There’s also a chance that display itself is damaged but there’s no visual sign of it.
You just need to be careful that the supplies’ outputs are completely isolated from mains. Otherwise you’ll end up with a lovely spark show.