There are plenty of EL84/6BQ5 with pin 8 internally connected to pin 2
(control grid). I have some RCA, GE, and unbranded Japanese that have this.
Fairly recent JJ and Ei that I have do not. Proceed with caution.

Best regards,

Steve Robertson

Eric Erickson wrote:

While all tube books say there's an internal connection for pin #8, I have
yet to find an EL84 that has anything connected here. I'd like to use the
socket pin to anchor a screen grid resistor for a ultra-linear amp. Does
anyone see any possible problems doing this?

Regards,
Eric

In article ,
"Eric Erickson" writes:
While all tube books say there's an internal connection for pin #8, I have
yet to find an EL84 that has anything connected here. I'd like to use the
socket pin to anchor a screen grid resistor for a ultra-linear amp. Does
anyone see any possible problems doing this?

Regards,
Eric


"I.C." means that the manufacturer is free to do anything he wants with
pin 8. No guarantees to the end user; just because you have 1000 tubes
with no connection on their pin8 desn't mean the 1001st will also leave
the pin uncommitted. Even those made by the same manufacturer.

I've found it to be much preferable to use something else for a tie point
-even if it means installing a one-terminal terminal strip. At least
that's something guaranteed to be under your control.

IC = "undefined".

----------------------------------------------------------------
Marty Dippel High Energy Physics
Sr. Systems Analyst The University of Chicago

Marty Dippel wrote:
In article ,
"Eric Erickson" writes:

While all tube books say there's an internal connection for pin #8, I have
yet to find an EL84 that has anything connected here. I'd like to use the
socket pin to anchor a screen grid resistor for a ultra-linear amp. Does
anyone see any possible problems doing this?

Regards,
Eric



"I.C." means that the manufacturer is free to do anything he wants with
pin 8. No guarantees to the end user; just because you have 1000 tubes
with no connection on their pin8 desn't mean the 1001st will also leave
the pin uncommitted. Even those made by the same manufacturer.

I've found it to be much preferable to use something else for a tie point
-even if it means installing a one-terminal terminal strip. At least
that's something guaranteed to be under your control.

IC = "undefined".

It occurs to me also that in a miniature tube, even a terminal that goes
"nowhere" is still within the bottle's vacuum; as a result, the stub of
the pin could conceivably act as a small anode, and draw a bit of
current if a voltage is applied to it.

It's quite a different scenario in octal tubes, where the socket is
separate from the bulb, and on which "NC" pins truly do not even connect
to any of the wires coming from the bulb.

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects: http://dogstar.dantimax.dk |
+--------------------------------------------+

"Steve Robertson" wrote in message
...
There are plenty of EL84/6BQ5 with pin 8 internally connected to pin 2
(control grid). I have some RCA, GE, and unbranded Japanese that have
this.
Fairly recent JJ and Ei that I have do not. Proceed with caution.

Best regards,

Steve Robertson

Steve:

Thanks for the input. I was looking at a sample of Russian, EI, JJ,
Mullard, & Sylvania EL84's. Each has no connection to pin 8.

Regards,
Eric

"Fred Nachbaur" wrote in message
...
It's quite a different scenario in octal tubes, where the socket is
separate from the bulb, and on which "NC" pins truly do not even connect
to any of the wires coming from the bulb.

Especially with sockets with missing pins

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

"Eric Erickson" wrote in message

....
socket pin to anchor a screen grid resistor for a ultra-linear amp. Does
anyone see any possible problems doing this?

Regards,
Eric

Hello Eric, Hullo, FellowRATs(TM)

What I don't get, is: why use a screen-grid resistor in an 'ultra
linear' design? I see problems there, 'cause the screen-grid will pull
a 20 - 25 % of the cathode current in that kind of setup. Anyhow, if
it's desired as a g2-stopper against VHF-oscillation, i wouldn't
connect it to such a long conductor dipping into the valve.

... and as well as some pre-posters already mentioned:

I) the (positive charged) stub of some connector dipping in the vacuum

II) i'd agree to put a not-miss-able note into the chassis near the
tube's location.

all in all it should work, though.

my 2 c

Sebastian

In article ,
"Tim Williams" writes:
"Fred Nachbaur" wrote in message
...
It's quite a different scenario in octal tubes, where the socket is
separate from the bulb, and on which "NC" pins truly do not even connect
to any of the wires coming from the bulb.

Especially with sockets with missing pins

Tim

Even then- I've seen some (usu. rectifier) tubes with a missing pin,
then other tubes of the same type with that pin present but apparently(??)
not internally connected. But then, as was previously stated, it may
be connected to the getter, or to some support structure, or ???

----------------------------------------------------------------
Marty Dippel High Energy Physics
Sr. Systems Analyst The University of Chicago

"Sebastian" wrote in message
om...
Hello Eric, Hullo, FellowRATs(TM)

What I don't get, is: why use a screen-grid resistor in an 'ultra
linear' design? I see problems there, 'cause the screen-grid will pull
a 20 - 25 % of the cathode current in that kind of setup.

I believe you're thinking about G3 (the suppressor grid), the grid usually
connnected to the cathode. On the high end, the screen grid MAY pull 2ma
when cathode current is 44ma, only 4.5%.

Anyhow, if
it's desired as a g2-stopper against VHF-oscillation, i wouldn't
connect it to such a long conductor dipping into the valve.

The intention it so suppress VHF oscillation (and drop the grid voltage a
volt or two) but can you clarify what you mean by 'a long conductor dipping
into the value'?

Eric