Quick Question EL34s Pin #1 in Marshall Style Amps

[ThreeChordWonder]

In my JTM45 copy, and I suspect others, pin #1 (suppressor grid) on the output tube - EL34 - socket is connected to pin #8 (cathode), which is connected to ground.

I've seen a YouTube video (yeah, I know) where pin #1 is not connected this way, but instead is  not grounded, and is used to "anchor" the otherwise hanging ends of the 5.1k resistor attached to pin #5 (control grid).

Simple question - is this okay?

 

[Ivan H]

A JTM45 used KT66 output tubes. These type (beam tetrode) tubes do not have a suppressor grid, rather beam forming plates that are internally connected to the cathode. Thus, pin 1 is not connected to any internal elements of the tube, so can conveniently be used as a tie point for the grid stopper resistor. Same goes for a 6V6, 6L6 (except the metal can types of these), a "true" KT77 & KT88 beam tetrode.
With the EL34's pin 1 "cannot" be used as a tie point. Same goes for the old USA made fat bottle 6CA7 beam tetrode, as the beam forming plates are internally connected to pin 1. Hope this helps. Cheers

 

[ThreeChordWonder]

Marshall started using EL34s in their JTM45s in 1966. At least according to Wikipedia.

So my question remains.

Is it okay to "anchor" the free ends of the 5.1k resistors attached to, and feeding, pin #5 (control grid) by using the otherwise grounded or unused suppressor grid on pin #1?

 

[Dblgun]

Is it okay to "anchor" the free ends of the 5.1k resistors attached to, and feeding, pin #5 (control grid) by using the otherwise grounded or unused suppressor grid on pin #1?

No, not with a EL34/6CA7 as @ Ivan H stated.

 

[ThreeChordWonder]

Thanks.

 

[StingRay85]

Use pin 6 for that

 

[Dblgun]

If you are looking for a way to secure the resistor you could use an insulated standoff that is also one of the fasteners for the tube socket. I have used this in Fender circuits but it could just as easily be used in your application. This is not my amp.

 

[ThreeChordWonder]

Use pin 6 for that

Already in use for the 1k 5W resistors to pins #4 (screen grids).

If you are looking for a way to secure the resistor you could use an insulated standoff that is also one of the fasteners for the tube socket. I have used this in Fender circuits but it could just as easily be used in your application. This is not my amp.

Sounds good. Ordered some nylon ones on eBay, about 5 bucks for 10.

 

[Ivan H]

Marshall started using EL34s in their JTM45s in 1966. At least according to Wikipedia.

So my question remains.

Is it okay to "anchor" the free ends of the 5.1k resistors attached to, and feeding, pin #5 (control grid) by using the otherwise grounded or unused suppressor grid on pin #1?

When I previously said that "with the EL34's pin 1 "cannot" be used as a tie point" I should have elaborated somewhat. Pin 1 is the suppressor grid. It's purpose is to reduce secondary emission, which is electrons bouncing back off the plate. The suppressor grid is usually grounded, though applying a "small" negative voltage to it is more efficient.
If pin 1 is used for a tie point for the grid stopper resistor "without" first disconnecting pin 1 from ground, the bias supply would be shorted to ground, meaning no negative bias voltage on the control grid. The power tubes would instantly red plate, most probably followed by meltdown in short order.
If pin 1 "is" disconnected from ground & used as a tie point for the grid stopper resistor, the negative bias voltage & any audio signal superimposed on it will be applied to the suppressor grid, causing it to act as a second control grid, rather than doing its intended job.
Cheers

 

[ThreeChordWonder]

When I previously said that "with the EL34's pin 1 "cannot" be used as a tie point" I should have elaborated somewhat. Pin 1 is the suppressor grid. It's purpose is to reduce secondary emission, which is electrons bouncing back off the plate. The suppressor grid is usually grounded, though applying a "small" negative voltage to it is more efficient.
If pin 1 is used for a tie point for the grid stopper resistor "without" first disconnecting pin 1 from ground, the bias supply would be shorted to ground, meaning no negative bias voltage on the control grid. The power tubes would instantly red plate, most probably followed by meltdown in short order.
If pin 1 "is" disconnected from ground & used as a tie point for the grid stopper resistor, the negative bias voltage & any audio signal superimposed on it will be applied to the suppressor grid, causing it to act as a second control grid, rather than doing its intended job.
Cheers

It was my intention to disconnect them from ground first. I wasn't going to hook up a wire straight to ground. Not even I am that dumb. Close, but...

Anyway. Just goes to prove that just because something is in a YouTube video...