Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: g-man on February 03, 2023, 01:29:46 pm

Title: V1 preamp tube DC on grid
Post by: g-man on February 03, 2023, 01:29:46 pm

Deleted

Title: Re: V1 preamp tube DC on grid
Post by: shooter on February 03, 2023, 01:55:44 pm

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

Title: Re: V1 preamp tube DC on grid
Post by: sluckey on February 03, 2023, 02:04:28 pm

bad tubes

Title: Re: V1 preamp tube DC on grid
Post by: pdf64 on February 03, 2023, 02:21:53 pm

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.

Title: Re: V1 preamp tube DC on grid
Post by: sluckey on February 03, 2023, 02:33:40 pm

Quote from: sluckey on February 03, 2023, 02:04:28 pm

bad tubes

And the tubes may work satisfactorily in another circuit.

Title: Re: V1 preamp tube DC on grid
Post by: g-man on February 03, 2023, 02:38:40 pm

Deleted