[Tubesforme]

The voltages were originally measured at the factory with meters with a sensitivity of 1000 ohms per volt. That's all they had at the time. Those meters loaded the circuit under test, resulting in voltage readings that were actually incorrect!

Today, we can easily buy digital multimeters with input impedances in the megohms per volt, which do not load down the circuit under test as did the old meters from ye olden days.

You can acquire an old early 1930s voltmeter...or find a low-end analog multimeter made by Calrad and sold in the 1970s...or maybe someone will measure the voltages in their working model 20 and share the results here. I no longer own any Model 20 sets.

I have never taken the voltage reading very seriously in any radio I repaired, except for transistors and tube bias. Otherwise most problems are fairly obvious. It looks like I have found my problem. While I live in a building built new, four years ago everything should be fine electrically. I have two other radios, both transistor, from the early 70's and they work just fine. However today I took the radio to a friend who repairs radios for a living, in Santa Clarita and the hum wasn't objectionable at all. The radio worked as it should. His suggestion to me was to get an isolation transformer and said that might not even be enough, it might be the area I am living in. So thanks to everyone for all your suggestions.