The Kay 703 is probably one of the more famous "widow maker" vintage amplifiers. "Widowmakers" are called such because they utilize a series filament design using the AC directly from the wall without a power transformer. There seems to be a lot of confusion out there about these simple, cheap, vintage amps. The hysteria is often so great that people think even looking at one will kill them. While the safety issues are often trumped up, there are still some ways amps such as the 703 can be made a bit safer.
The 703 has an isolation step up transformer with a single winding for the tube plates, but filaments are still not isolated from the current coming out of the wall. To resolve the slightly increased danger this poses, we will equip this amp with a 3-prong, grounded power cord and add a fuse in series with the power switch. We will also clean the tube sockets, input jacks, and check out the schematic. Finally, we'll plug her in and check out the tone with a Fender Telecaster.