Before I Drive Myself Nuts!!

[Bushbaby]

Ok,
Last post before bed!
I have checked the voltage setting - its set at 240/260, the highest setting.
I have connected the Avo across the plug and removed a valve (well several but one at a time) each time - about 200R reading, the meter needle does not move. I have checked the lamp limiter again - the light is on and doesn't dim.

Now what i have checked is another pot of the same type (not connected to the radio of course). I connected the same two terminals as I wired for the mains connections in the radio - 200R reading again. I therefore assume I've selected the wrong two terminals! 64 thousand dollar question and I think I know the correct answer - the terminal for +ive to the mains should have the highest resistance when measured to the chassis. Is this correct? Does it matter which one of the pairs is taken for mains connection??

If I've time I shall have another look tomorrow.

Regards

Rob