V1 preamp tube DC on grid

[g-man]

Deleted

[shooter]

guessing it's not DC since it would be there with good tubes and bad
probably loose tube/socket or input jack that's iffy

[sluckey]

bad tubes

[pdf64]

Just to expand on that, even good valves might exhibit a tiny bit of grid current.
That’s why there’s an upper limit on grid circuit resistance.
Also, as anode voltage reduces, grid current will tend to increase.

But if with a ‘limit or lower’ grid circuit resistance there’s much VDC on the grid, eg >0.1V, then the valve might be regarded as no good.

[sluckey]

bad tubes

And the tubes may work satisfactorily in another circuit.

[g-man]

Deleted