[morzh]

If you can post the video and provide the link, I will try to make sense of it.
I also have an open 18 (124 but the differences are minor), that works (waiting on the shadow meter replacement).

Also the advice Ron gave you - heed it. Unless you know something about electronics and especially about tubes, as the voltages there can simply kill you, don't just go in and try to fix stuff. Read something first. You have to know at least some basics.