I realize that there was a problem with putting a screen grid in the tube (tetrode) that was charged positively, as the electrons would strike the plate with such velocity that they'd bounce back and collect on the control grid, as well as other places. This would cause oscillations. The pentode, with its supressor grid (negatively charged) stopped this problem, as the supressor helped keep the electrons on the plate.
That said, would a screen mesh plate improve oscillation problems by allowing the electrons to fly through the mesh, and then perhaps be attracted back to the plate once they reached the other side? If this is so, as many electrons would be allowed through the plate, they would not likely bounce back off of it, and those that made it through would have to travel through it again to cause any trouble back inside. I doubt this would happen because the mesh plate is so positive. That said, all electrons that passed through the plate would likely collect back on it. So, if this is the reason, why were they also used in triodes, such as the 24A. I know they were used on the 27A radio tubes. 27A is a tetrode, which would have the oscillation trouble without the supressor. 24A is a triode. This tube is not as likely to have spurious oscillations. Furthermore, the screen mesh plate was used in pentodes of the 1950s and 1960s. I suppose if it works well with tetrodes, why not use it with pentodes, right?
Anyway, if someone knows the details of this, I am curious as to why such tubes were made.
Thomas
:I was wondering if anyone had the exact technical reason as to why mesh plate tubes were produced. I know they were produced quite a bit in the 1920s and early 1930s, and somewhat after that, but not quite as common. I've also seen them in various televisions and radios of the 1950s and 1960s, especially when the tubes or appliance has been made somewhere in Europe, such as Germany or Holland, and possibly other countries (England produced some mesh plate tubes).
:
:I realize that there was a problem with putting a screen grid in the tube (tetrode) that was charged positively, as the electrons would strike the plate with such velocity that they'd bounce back and collect on the control grid, as well as other places. This would cause oscillations. The pentode, with its supressor grid (negatively charged) stopped this problem, as the supressor helped keep the electrons on the plate.
:
:That said, would a screen mesh plate improve oscillation problems by allowing the electrons to fly through the mesh, and then perhaps be attracted back to the plate once they reached the other side? If this is so, as many electrons would be allowed through the plate, they would not likely bounce back off of it, and those that made it through would have to travel through it again to cause any trouble back inside. I doubt this would happen because the mesh plate is so positive. That said, all electrons that passed through the plate would likely collect back on it. So, if this is the reason, why were they also used in triodes, such as the 24A. I know they were used on the 27A radio tubes. 27A is a tetrode, which would have the oscillation trouble without the supressor. 24A is a triode. This tube is not as likely to have spurious oscillations. Furthermore, the screen mesh plate was used in pentodes of the 1950s and 1960s. I suppose if it works well with tetrodes, why not use it with pentodes, right?
:
:Anyway, if someone knows the details of this, I am curious as to why such tubes were made.
:
:Thomas
I'm sure you're right in guessing that these mesh elements had something to do with oscillation reduction. The same is probably true of later tubes, too.
:I was wondering if anyone had the exact technical reason as to why mesh plate tubes were produced. I know they were produced quite a bit in the 1920s and early 1930s, and somewhat after that, but not quite as common. I've also seen them in various televisions and radios of the 1950s and 1960s, especially when the tubes or appliance has been made somewhere in Europe, such as Germany or Holland, and possibly other countries (England produced some mesh plate tubes).
:
:I realize that there was a problem with putting a screen grid in the tube (tetrode) that was charged positively, as the electrons would strike the plate with such velocity that they'd bounce back and collect on the control grid, as well as other places. This would cause oscillations. The pentode, with its supressor grid (negatively charged) stopped this problem, as the supressor helped keep the electrons on the plate.
:
:That said, would a screen mesh plate improve oscillation problems by allowing the electrons to fly through the mesh, and then perhaps be attracted back to the plate once they reached the other side? If this is so, as many electrons would be allowed through the plate, they would not likely bounce back off of it, and those that made it through would have to travel through it again to cause any trouble back inside. I doubt this would happen because the mesh plate is so positive. That said, all electrons that passed through the plate would likely collect back on it. So, if this is the reason, why were they also used in triodes, such as the 24A. I know they were used on the 27A radio tubes. 27A is a tetrode, which would have the oscillation trouble without the supressor. 24A is a triode. This tube is not as likely to have spurious oscillations. Furthermore, the screen mesh plate was used in pentodes of the 1950s and 1960s. I suppose if it works well with tetrodes, why not use it with pentodes, right?
:
:Anyway, if someone knows the details of this, I am curious as to why such tubes were made.
:
:Thomas
Thomas
:This will probably confuse the issue even more. On some older tubes, like types 24A and 6K7, the outer mesh cylinder isn't the plate. It's an extension of the outermost grid (grid 2 in tetrodes, grid 3 in pentodes). The connection is made at the upper binding posts. If you look at these tubes from the base up, you will see another cylinder inside the mesh cylinder. *That* is the plate. (You may need a flashlight to see it.) Some schematics from the early 30s show a literal interpretation of this by showing two interconnected grids stradling the plate.
:
:I'm sure you're right in guessing that these mesh elements had something to do with oscillation reduction. The same is probably true of later tubes, too.
:
::I was wondering if anyone had the exact technical reason as to why mesh plate tubes were produced. I know they were produced quite a bit in the 1920s and early 1930s, and somewhat after that, but not quite as common. I've also seen them in various televisions and radios of the 1950s and 1960s, especially when the tubes or appliance has been made somewhere in Europe, such as Germany or Holland, and possibly other countries (England produced some mesh plate tubes).
::
::I realize that there was a problem with putting a screen grid in the tube (tetrode) that was charged positively, as the electrons would strike the plate with such velocity that they'd bounce back and collect on the control grid, as well as other places. This would cause oscillations. The pentode, with its supressor grid (negatively charged) stopped this problem, as the supressor helped keep the electrons on the plate.
::
::That said, would a screen mesh plate improve oscillation problems by allowing the electrons to fly through the mesh, and then perhaps be attracted back to the plate once they reached the other side? If this is so, as many electrons would be allowed through the plate, they would not likely bounce back off of it, and those that made it through would have to travel through it again to cause any trouble back inside. I doubt this would happen because the mesh plate is so positive. That said, all electrons that passed through the plate would likely collect back on it. So, if this is the reason, why were they also used in triodes, such as the 24A. I know they were used on the 27A radio tubes. 27A is a tetrode, which would have the oscillation trouble without the supressor. 24A is a triode. This tube is not as likely to have spurious oscillations. Furthermore, the screen mesh plate was used in pentodes of the 1950s and 1960s. I suppose if it works well with tetrodes, why not use it with pentodes, right?
::
::Anyway, if someone knows the details of this, I am curious as to why such tubes were made.
::
::Thomas