Normal for voltage at speaker terminals at turn on?

Ok, I got this Dynaco SCA-80Q, and just like any other vintage equipment. I measure terminal voltage before hooking up speakers to it.
What's odd is typically I get at most 50-60 to even 100 mV on most vintage receivers at turn on and it gradually subsides thereafter some to very low 5mV.

But not with this Dynaco SCA-80Q, it gets around 30volts at each terminal at turn on, and gradually lowers down. I'm not confident on hooking up my speakers with these voltages.
The owner says he did but gets some kind of distortion on the sound. He said it might just be his motorhome as it is where he is using it.

Now the question is it normal for around 30volts at the terminals at turn on as it gradually lowers. Or is there something wrong with the unit?
Anything I can do to alleviate such?
Thank you.