Warning for NOS EL84/6BQ5 (or UOS) in modern amps

[g1]

Apparently some modern amps with EL84 are using pin1 as a tie point, but pin1 is specified as Internal Connection for some old production EL84 tubes, so this can create problems.
I'm not one who shops for NOS EL84/6BQ5, but I do sometimes use old worn out/microphonic tubes for test purposes which could create issues.
There is a list of offending amps in the following link:

Modern EL84 amps and NOS EL84s | KCA NOS Tubes & Amplifier Repair

[pdf64]

My old AC30 had a link between terminals 1 & 2 of the EL84 sockets.
That never caused a problem with the various Brit and Russian used, but I removed the links a few years ago when I became aware of the issue, just in case.
The links seemed pretty pointless.

[Enzo]

It terminates the otherwise floating piece of metal inside the tube. it may not ever matter, but... Kinda like that extra shield wire coming out of a power transformer.