Mine is 123-125 VAC most of the time, even on hot days, since the utility replaced the Truman-Era pole transformer. It was 112-115 and everything was happy, but had to upgrade from a 60 fused service to 200 amp main circuit breaker panel and meter to install central A/C.
What's worse is that this is acceptable per the utility and rules of service because it is within 5% of 120. So, even if there was a higher primary winding tap on the pole trans, which there isn't, the utility would not adjust it anyway.
Obviously, most of vintage electronics is designed for 117 volts maximum. Some of the most concern are 1930-40s radios and tube TVs with power transformers. And, unlike some later tube color sets, most lack a hi-line tap on the transformer.
My initial approach was to install an inrush limiter (thermistor) GE CL-90 is rated 2 amps and the CL-70 is 4 amps for those big color TVs. Unfortunately, these do not drop more than a volt after heating up.
Ill assume a step-down trans or variac for each set is not practical or cheap. What is your tech-seasoned opinion on the following proposed solutions?
1. A "buck", auto transformer using a common 120-12.6v filament transformer, assuming the secondary is rated for the same current as the intended load. Less heat but....
2. Series resistors. for example, to drop 10 volts at 2 amps load, a 5 ohm 20 watt resistor is needed. Or more practically, four 2.7 ohm 10 watt resistors in series/parallel. Lower cost but...