The mixer box doesn’t take vacuum tubes, its much too small. It basically has connections for the transformer, track, and the turntable output. It likely relies on amplification from a stereo system to boost the power.
The mixer box contains 2-3 basic circuit components which includes at least one capacitor. I opened the case on mine but could not get at the components without unsoldering everything because they are wrapped up in paper to insulate them. Since my set is mint, I really don’t want to disect it.
