something I found for sale on the web Are you buying this guys pitch?

[W2PFY]

PHILIPS TB5/2500, MADE IN FRANCE BY AMPEREX, UNUSED. THIS TUBE HAS THE GRID BROUGHT OUT TO 3 BASE PINS. THE PINS ARE DESIGNED SO THAT THOSE NOT REQUIRED CAN BE SNAPPED OFF. ON THIS TUBE  THE 2 SPARE GRID PINS HAVE BEEN SNAPPED OFF, LEAVING TWO PINS FOR THE FILAMENT AND ONE FOR THE GRID.

[K1ZJH]

I think I'd like ALL of the pins to be there. Especially for bypassing.

[w4bfs]

good bye vacuum ... beefus

[WQ9E]

He must be a cousin of the guy who removed the "glass shells" from the audio tubes for cleaning.

The multiple grid connections are used to reduce the total inductance associated with the grid connection (the multiple connections put the inductance of each in parallel).  They weren't meant to be optional.

I wonder if the seller has disposed of his extra unneeded  fingers, toes, kidney, lung, etc. 

Rodger WQ9E

[k4kyv]

Reminds me of the Johnson desk kilowatts and other plate modulated rigs with the modulator section removed to convert it to a "good cw rig".  That used to be commonly seen at hamfests in the early to mid 60's when the big push for slopbucket was on.

[KB3DKS]

Philips Data shows this tube to have only 4 pins with two for the grid. So only one is missing. See,
http://tubedata.milbert.com/sheets/089/t/TB5-2500.pdf

Bill
KB3DKS in 1 Land

[K1ZJH]

Philips Data shows this tube to have only 4 pins with two for the grid. So only one is missing. See,
http://tubedata.milbert.com/sheets/089/t/TB5-2500.pdf

Bill
KB3DKS in 1 Land

Wrong data sheet. It is a TB4/1250, and has (errr... HAD) three grid pins
originally.  The photo shows two missing pins out of five..

http://tubedata.milbert.com/sheets/089/t/TB4-1250.pdf

Pete

[KB3DKS]

Philips Data shows this tube to have only 4 pins with two for the grid. So only one is missing. See,
http://tubedata.milbert.com/sheets/089/t/TB5-2500.pdf

Bill
KB3DKS in 1 Land

Wrong data sheet. It is a TB4/1250, and has (errr... HAD) three grid pins
originally.  The photo shows two missing pins out of five..

http://tubedata.milbert.com/sheets/089/t/TB4-1250.pdf

Pete

 Ooops, I should have looked at the pix closer not the text.
Guess the guy needs glasses too !
Nice tube... too bad...

Bill

[AB2EZ]

Removing 2 of 3 pins reduces grid current partition noise.

Each electron has only one path. In a stock tube, each electron has to choose one of three paths, and if the paths have slightly different resistances, this can result in an enhancement of the normal shot noise associated with the grid current.

The enhancement of the shot noise associated with the grid current in a stock tube is the reason why a tube like this is particularly attractive for audiophile applications... where soft music passages are vulnerable to grid partition noise.

Stu

[k4kyv]

Maybe someone cut off the pins in hopes of salvaging some oxygen-free copper.