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previous: Whit A.S. Nothing compl... -- 10/4/1999 1:39 PM

Re: Triode switch

10/4/1999 2:09 PM
kg	Re: Triode switch To add a bit to Whit's post: Measure the normal screen voltage supply. Compare it to the plate supply voltage(s) at the leads of the OPT. If they are largely the same, then the current through the tube will not change when you switch from P to T. This is because Vg2 isn't changing much, and that has the most effect on Ip. I suggest you leave the screen stoppers right on the sockets, and connect THOSE to the center of the DPDT. Those will serve to limit overloading the screens. It is important to note, however, that screen current will drop quite a bit when switching to triode mode. This is because the screen is NEVER more positive than the plate when connected as a triode. Contrast that to the pentode connection where the screen is usually higher in potential than the plate when signals are applied. For this reason the usual series Rg2 is much lower for triode mode, say hundreds of ohms as opposed to thousands. As usual though the increased series resistance won't really do anything but increase reliability. Ken

10/4/1999 2:09 PM

Re: Triode switch

To add a bit to Whit's post:

Measure the normal screen voltage supply. Compare it to the plate supply voltage(s) at the leads of the OPT. If they are largely the same, then the current through the tube will not change when you switch from P to T. This is because Vg2 isn't changing much, and that has the most effect on Ip.

I suggest you leave the screen stoppers right on the sockets, and connect THOSE to the center of the DPDT. Those will serve to limit overloading the screens.

It is important to note, however, that screen current will drop quite a bit when switching to triode mode. This is because the screen is NEVER more positive than the plate when connected as a triode. Contrast that to the pentode connection where the screen is usually higher in potential than the plate when signals are applied.

For this reason the usual series Rg2 is much lower for triode mode, say hundreds of ohms as opposed to thousands. As usual though the increased series resistance won't really do anything but increase reliability.

Ken

Replies:

A.S The difference between plate and sc... -- 10/4/1999 9:10 PM