[morzh]

I am not sure I understood: so, the radio now works well and the noise only appears when you touch the 77' grid cap, or, as you described it in your first post, it comes all the time but goes down as the radio warms up.

It is expected to have a fairly loud hum and buzz when a grid of a 1st audio is touched.

You could also film the performance and the noises, put it on youtube and give us the link.