With this you can power your favorite antique valve radio!

This power supply unit is primarily designed for use with battery powered valve radios that require a high-tension (HT) supply of about 90 volts at a current consumption of up to 10 milliamps or so. The batteries for these receivers are now unobtainable, and they were pretty expensive when it was possible to buy them. The solution used here is to have a d.c. to d.c. converter that steps-up the output from a 6V battery to about 90V.