But I did find B&K Model 707 factory changed from #83 to two 1A 600-PIV 1N4006 rectifier diodes. They added 56Ω resistor at the panel meter, I think the panel meter is 1mA 100Ω movement. This might be for the higher voltage? Also from 1MEG to 2MEG pot for SHORT SENSITIVITY.
Many old test equipment schematics here: https://www.pacifictv.ca/wanted.htm and 707 tube chart too. It looks like near the same as the 700.
I think the different resistors come from different transformers or meters, there's a warning on tubesound.com about this.
I'll probably not use 707 tube charts with the 700 because I couldn't find the exact differences and I don't want to blow up a tube because the sockets are wired differently....
The latest tube chart specifically for the 700 is here:
https://bama.edebris.com/manuals/b&k/700/Anyway: With the original #83 in and taking the same measurement as before: 200 VDC with a *cold* #83, around 180 VDC after warming the tube up for 30 min - where also the clipping seems to have gotten less worse.
The reality is there is no 'spec' on that supply rail used for 'GM Plate test' - the schematic level of '200' is effectively an advisory level, especially as the tester has no fine adjust for mains voltage (it uses another technique to alleviate mains voltage variation). So as floobydust recommends, it will be the Gm measurement capability, which for this tester is a bit wishy washy as far as absolute level - so will come down to consistency for a particular type of tube you may have tens or hundreds of, and how you interpret some that are replace versus good, or to grade valves in a batch as better than others.
You could measure the winding resistance of each of the 193V secondary windings, and then use PSUD2 simulation to assess the change in rectified voltage with loading, as a way of appreciating the change in reading with and without a scope probe connected. To me, adding a 1Mohm scope 1:1 probe to a 10Mohm DMM load is not likely to see more than 1-2Vrms change, but you indicate the change with/without scope probe added was 'drastic'.
From which points do I take these measurements? As you said, the meter is wishy washy and it does what I want it to do, weed out bad tube from good ones. I'll probably learn with experience what the results mean from using it and as I don't need to grade them at precise Gm levels I think we can conclude that the circuit is working as intended.
I have never used PSUD but I attached a file in case anyone wants to play with it. The resistances were as follows:
RED - 327R - GND - 226R - BRN / RED - 625R - BRN
With circuit transfer switch on: RED - 195R - GND - 275R - BRN / RED - 471 - BRN
I'll probably still use the #83 SS replacement, it draws 30W less, doesn't bake the components inside and allows me to hide a smaller transformer inside the case for 230V operation