Pentod tubes that have 8 pins are often used for output tubes when making tube amplifiers. 5881/6L6GC/EL34 etc.
These tubes have same pinout. And have same unused pins.
I know pin 1 and pin 6 are not used.
I have a question from here.
In many tube guitar amp layouts, pin 6 is used to install grid stoppers connected to pin 5 or screen resistance connected to pin 4.
However, pin 1 is often tied together with pin 8 (cathode) and connected to the ground.
I often connect the parts fitted to the screen grid and grid stoppers directly to the pins, rather than on the board.
However, as with the ordinary layout, I connect pin 1 to the ground with pin 8.
Thus, only one dummy pin remains, making it possible to hold either the grid stopper or the screen resistor to the dummy.
Thus, only one dummy pin remains(pin6), I'm in a situation where either screen grid or grid stoppers can use a dummy pin.
So, there is only one dummy pin left (pin6), I am in a situation where only one of the screen grids or grid stoppers is available.
I think pin 1 can also be used as a dummy pin with not connected to pin 8. Is there a special reason why many people don't use pin 1 like this?
Questions bout 6L6gc unused pins.
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psychepool
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Questions bout 6L6gc unused pins.
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Last edited by psychepool on Mon Mar 23, 2020 5:15 am, edited 1 time in total.
Re: Questions bout 6L6gc unused pins.
For EL34, pin 1 is connected to grid3, and must be tied to the cathode for best operation:
https://frank.pocnet.net/sheets/030/e/EL34.pdf
https://frank.pocnet.net/sheets/030/e/EL34.pdf
I build and repair tube amps. http://amps.monkeymatic.com
Re: Questions bout 6L6gc unused pins.
Pin 1 is not connected to anything on a 6L6 beam tetrode (unless you have an old metal can tube), so you can use it anyway you want. Fender was fond of mounting the 1500Ω grid stopper resistor between pin 1 and pin 5.
But pin 1 is connected to the suppressor grid in the EL34 pentode and it needs to be connected to ground or a negative voltage. It's most commonly connected to pin 8 (cathode). YOU CANNOT USE PIN 1 FOR ANYTHING ELSE!
But pin 1 is connected to the suppressor grid in the EL34 pentode and it needs to be connected to ground or a negative voltage. It's most commonly connected to pin 8 (cathode). YOU CANNOT USE PIN 1 FOR ANYTHING ELSE!
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psychepool
- Posts: 286
- Joined: Fri Apr 18, 2014 8:29 am
Re: Questions bout 6L6gc unused pins.
OK, I get it.
To be honest, I didn't have much chance to use EL34.
I have been used it in commercial amps but not in DIY amplifiers.
The 8-pin Pentode tubes that I used in DIY amps were 6V6/6L6GC/5881.
On many 6L6GC amplifiers, when replacing output tubes with EL34, they easily replaced with very minor changes of values.
So I think I was confusing EL34 with 6L6GC/5881 pinouts being the same.
Thank you for your answers!
To be honest, I didn't have much chance to use EL34.
I have been used it in commercial amps but not in DIY amplifiers.
The 8-pin Pentode tubes that I used in DIY amps were 6V6/6L6GC/5881.
On many 6L6GC amplifiers, when replacing output tubes with EL34, they easily replaced with very minor changes of values.
So I think I was confusing EL34 with 6L6GC/5881 pinouts being the same.
Thank you for your answers!
Re: Questions bout 6L6gc unused pins.
The 6V6/6L6/5881 tube is not a pentode. It's a beam power tetrode. There is a difference.psychepool wrote: ↑Mon Mar 23, 2020 5:40 am The 8-pin Pentode tubes that I used in DIY amps were 6V6/6L6GC/5881.
To do this you must connect pin 1 to pin 8. Usually just requires tweaking the bias. But note that pin 1 is no longer unused.On many 6L6GC amplifiers, when replacing output tubes with EL34, they easily replaced with very minor changes of values.