[DaleHCook]

Extech MN35 DMM

That would appear to be a perfectly serviceable DMM, with 10 meg DC impedance and 4.5 meg AC impedance.

Very few of us use an actual 1,000 ohms per volt AC/DC meter. Although I own one in my Triplett 1167-A Set Tester, ca. 1935, I do not use it - my 1167-A is a shelf queen.

Any high-impedance DMM can easily be turned into a 1,000 ohms per volt AC/DC meter. Say you want to measure an expected DC voltage of 350 volts. You will use the 600 VDC range of your Extech. Multiply the maximum voltage of that range (600) times 1,000 ohms to get 600,000 ohms. If you shunt that value across the input of your Extech, you turn it into a 1,000 ohms per volt DC meter. A standard 5% 620k resistor will work well enough.

Just for giggles I like to have shunt boxes in the shop for my principal bench meters - a Keithley 4½ digit True RMS bench DMM, and an HP 427A analog multimeter. As a rule I almost never use those shunt boxes, because any decent high-impedance digital or analog meter should measure almost any voltage in an old radio chassis close enough for jazz, if a little high. The voltages you marked in boldface would seem to be definilty bad in any case, with the exception of the lowest voltages such as bias voltages. Those would likely read a lot closer with the loading of a 1,000 ohms per volt DC meter.

You need to work backwards from the bad readings toward the power supply to figure out what is causing the bad readings. A set whose paper and electrolytic caps have all been replaced, whose tubes do not test bad, and whose inductor and transformer windings have been correctly ohmed out, will be easier to troubleshoot.