On all of the radios that we restore, Is it a huge deal running 120 volts AC on these radios that were rated at 115-117 volts? Like for instance my Zenith 6-d-311 that has a ballast tube. It states on the schematics that the supply voltage is 115 volts AC. When I check my wall voltage, It is a constant 120.1-120.5 volts AC. Should I be worried that this is going to cause problems? Should I be installing a power dropping resistor to bring the voltage down or will it be okay?

:On all of the radios that we restore, Is it a huge deal running 120 volts AC on these radios that were rated at 115-117 volts? Like for instance my Zenith 6-d-311 that has a ballast tube. It states on the schematics that the supply voltage is 115 volts AC. When I check my wall voltage, It is a constant 120.1-120.5 volts AC. Should I be worried that this is going to cause problems? Should I be installing a power dropping resistor to bring the voltage down or will it be okay?

Troy:
I wouuldn't worry about it. The ballast tube should compensate for the difference, and the Voltage is less than five per cent higher than rated, anyhow.
Lewis
:

This level of overvoltage won't significantly lessen the life of your tubes. They were designed to accommodate heater overvoltage to some degree without affecting their useful lifespan.

The main enemy of tube longevity in transformerless sets like yours is inrush current: when a set is first turned on, the heaters are cold and so are relatively low resistance. This means that a fairly large current surge flows through the filament string prior to heater warmup when you flip the "on" switch. This surge, repeated often enough, will eventually open up the weakest heater in the string. It has been estimated that turn-on current surges reduce the life of tubes by about 50%.

This can be prevented by installing a surge-limiting device in the set such as a surgistor. The trick in using these is selecting one that is matched to the normal current draw of your set; otherwise it will not operate correctly and will drop excessive voltage across itself.

However, if the set is going to mainly be a "shelf queen" and not a daily player, I wouldn't worry about it. If the set will get used extensively and flipped on and off many times a day, it is something to consider.

a fairly large current surge flows through the filament string prior to heater warmup when you flip the "on" switch. This surge, repeated often enough, will eventually open up the weakest heater in the string. It has been estimated that turn-on current surges reduce the life of tubes by about 50%.
:
:This can be prevented by installing a surge-limiting device in the set such as a surgistor.

It seems to me the dial lamp serves as a surge protector on some sets, no?
Maybe add a bulb to the heater string?

Well, not really. Dial lamps suffer from the same low-resistance-when-cold effects as tube heaters. Most dial lamps on transformerless sets are connected in shunt across part of the rectifier tube heater, so I suppose that it could be argued that they offload a little current from that segment of the rectifier heater; but the rest of the set takes the full surge current hit.

This would be the time to instal a CL-90 Thermistor in series with the heater string. Cold start is 70 volts. When warm a drop of two volts. This takes most of the surge off the ballast tube. Adds more life.

Likely a better choice than a surgistor for a small appliance like a radio.

I install a CL-90 on every old AC radio I work on. A couple of volts drop, at steady state, when they are warm helps reduce modern voltages, too. The CL-90 is fine for almost any tube-type radio - well, maybe not those 20-tube big-Berthas. (There are other CL versions appropriate for such current hogs.)

The CL-90, and its sister versions were initially G.E. products. Something tells me that the CL line was sold to another manufacturer? Not sure. If you Google CL-90, you will find them.

They are just thermistors, as are often used for temperature measurement. The higher the temperature, the lower the resistance.

Most tubes that fail burn out at turn on, just like incandescent lamps.