EL84 available pins? Consensus?

[eschertron]

So after looking at the JJ data sheet, and seeing that pin 1 is NOT marked with i.c. (or used for any other purpose) I decided to use that pin to land the screen resistor. Running from pin 9 to 1, what could be more natural? THEN I happened to look at a Phillips data sheet that indicates i.c. for pin 1.

... and so it snowballs. A review of querys and posts - including one Steve A. started back in 2000 - leaves me guessing if ANY pins are routinely used as tie points. Is using the base of an EL84 as a terminal strip strictly forbidden? Who has tried and lived to tell?

[Chuck H]

I did it with my personal el84 amp. But that doesn't count I guess because I know it's done that way and I know how to avoid problems. I've also done some el84 amps for customers and I did not use the socket pins as tie points for the most obvious reason. A lot of vintage el84's and their equivalents and variants Do use internal connections to otherwise unused pins. I even read that early in that tube types development some custom and/or special purpose designs were made that still carried the moniker el84 with no suffix though they had different internal connections doubled to pin 6 and such. I don't know how possible it is to get a weird el84 that won't work with the typical omitted connections to pins 1, 6 and 8, but I know damn sure that if I sell an amp that uses those pins as isolated tie points someone will plug one of these weird tubes into it!

So that's my position. Do whatever you want for your own amp but if the amp is for anyone else just do what every other company with public designs does and don't use pins 1, 6 or 8.

[stormbringer]

I did in on my own build too - and lived to tell about it here.

However, after doing it I did some googling and also asked one or two trusted advisors and then moved the tie point off pin 1. One person's opinion was that some pins need to remain unused due to the small footprint of the EL84. Seems like a reasonable - and safe - opinion to me.

[eschertron]

OK, so no use of pins on an EL84 as tie points. The data sheet for the JJ tubes that I have is the ONLY tube data sheet that indicates any open pins. No other sources that I've seen show any available.

I've put my screen stoppers on the eyelet board. Followup question: If I twist the screen supply wires together, will that make a bit of difference? I'm thinking there will be a small voltage, in the single-digits AC range, between the two screen wires after the voltage drop across the two screen resistors. The voltage 'drop' will of course be out of phase, and so the twisted wires might help reduce AF crosstalk in nearby circuits. So I get points for neatness. Any other real benefit?