Bottlehead Forum

General Category => Technical topics => Topic started by: Jim R. on May 26, 2011, 10:48:50 AM

Title: description of pinout for el84?
Post by: Jim R. on May 26, 2011, 10:48:50 AM

Folks,

I'm working on my el84 amp today and trying to figure out a problem and I cannot find a descriptive pinout of the el84 anywhere -- just pictures.

Can somebody do me a favor and list the pins and their functions so I can try to figure out what this particular designer did with this amp?

Thanks,

Jim

Title: Re: description of pinout for el84?
Post by: Grainger49 on May 26, 2011, 10:53:42 AM

Ok, the plate is pin 7.  The top grid, nearest the plate, (suppressor?) is connected to the cathode internally and they are on pin 3.  The center grid, the control grid I think, is pin 9.  The grid closest to the cathode is connected to pin 2.  And the heaters are connected to pins 4 and 5.

Sorry, I'm not that great at remembering the grid names.

Title: Re: description of pinout for el84?
Post by: JC on May 26, 2011, 11:46:16 AM

Actually, Grainger, I the grid nearest the cathode is the "control grid", or just "grid" in a triode.  Next is the "screen grid", since it was said to "screen", or shield, the control grid from the plate.  It is generally operated at a positive Voltage somewhat lower than the plate.  The grid closest to the plate is the "suppressor grid", as you said, because it was said to "suppress" the secondary emissions that occur when the electrons hit the plate.

Keep in mind, a lot of the nomenclature is a product of its time!

Title: Re: description of pinout for el84?
Post by: Grainger49 on May 26, 2011, 12:58:42 PM

If I had just looked at the Eros schematic I would have known which was the control grid.  D'oh!

Jim, thanks for the help!