[morzh]

Yes, the meter should use AC setting. If you do not have 0-30V, then you use 0-50V. It should not peg out, but can possibly have initial throw.
If it does, start from a larger scale like your 250VAC, and once the transition passes, go back to 50VAC.
The scale itself is not important, it is just, as always, you want to use the lowest possible one to have better resolution / track minute pointer movements.

You also should show the settings you use on your photos, else we only see it on "Off".
Also, could you please refer to the pins by function and not just the number. Else you send people to figure out "what are the pins 3 and 8". I know they are K and A., but still.

I am not sure what you are doing with this meter. If the meter is OK, (and the convention is Black is Common).
Your Black lead should be in your COM- jack.
Your red lead should be in your OUTPUT jack.

Your range should be set to appropriate AC Volts and your Polarity switch should be at the top (DC+, Ohms and ACV) position or else the polarity will reverse.

This is it. If it still pegs out, and stays pegged out, your DC blocking cap could be shorted.


And. If you connect to the 6K7 grid cap but remove 6A8 grid cap...guess what happens? (a hint: no, your meter won't react).


PS. Personally, I always prefer the meter on AC volts across the output of the power xfmr (or the speaker which is the same). Today's DMMs are fairly accurate and you will see the change.