Testing Voltages on Antique Radios & TV Sets.

You are correct. Not all schematics specified this, but it was mentioned  in some companies factory service data, but after a certain point in time, they usually omitted this data.
 In the newer schematics, like Sams and factory data, it was typically mentioned in the alignment data.

I think it would be fairly safe to Word is Censored on the 1K ohm/volt meter usage it was likely good up until the late 1940's.
Then VTVM's and higher impedance test meters became available.

Line voltages were a lot lower back then also. Between 105 and 110VAC generally. Now voltages are 120-125. This can throw off voltage readings. (Also a good reason to use higher voltage rated capacitors, especially filter caps).

Best to use a variable transformer set for 110V for troubleshooting.

Frank, I am gonna assume that not all schematics tell you this info. Is there a a certain assumption to make if nothing is said about this? Just curious.

One of Cliff's comments brought the following to mind.

As a beginner, back in the age of stone knives and bearskins, I was trying to troubleshoot an old radio.

 However the voltages were quite a bit different than the schematic showed. I was puzzled.

I spoke to an older ham friend and he looked at the schematic & voltages and asked me one question: "What is the input impedance of your VOM or VTVM?". 
(Huh? what has that got to do with it? I thought).

I said it had a "10 meg input impedance."

He said: " Look at the line on the bottom of the schematic. it says: Voltages taken with a 1000 Ohm per Volt meter" Your meter is 10 Meg. It IS going to read different, as it is not loading the circuit the same". Problem solved with an old VOM of 1K impedance.

Just thought I would toss this out there, as I probably have not been the first person to experience this. This can be CRITICAL in trying to align a radio or TV set.



Also FYI most voltages in old radios or TV sets are +/- 20 %.  This is due to the variations in parts tolerances. This being noted:

A tech once told me of his worst nightmare repair, a piece of military equipment that no matter what he and the other techs did, it failed to work.

Finally he checked the tolerances of the parts in the unit. They were all at one end of the marked values of 10 & 20%. The odds of this are incredibly small of this happening, as most of the equipment was designed to work + or - 20% parts tolerances. However when all the parts are at one end of the tolerance, things do not work as designed.

Changing out numerous parts with ones close to the median tolerance brought the unit back to life.

Likely you will never run into this problem, but it is good to keep in mind that it can and DID happen.