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Title: something I found for sale on the web Are you buying this guys pitch? Post by: W2PFY on April 10, 2009, 08:33:42 AM 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.
Title: Re: something I found for sale on the web Are you buying this guys pitch? Post by: K1ZJH on April 10, 2009, 09:28:22 AM I think I'd like ALL of the pins to be there. Especially for bypassing. ;D
Title: Re: something I found for sale on the web Are you buying this guys pitch? Post by: w4bfs on April 10, 2009, 09:35:54 AM good bye vacuum ... beefus
Title: Re: something I found for sale on the web Are you buying this guys pitch? Post by: WQ9E on April 10, 2009, 10:22:51 AM 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 Title: Re: something I found for sale on the web Are you buying this guys pitch? Post by: k4kyv on April 10, 2009, 08:34:18 PM 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.
Title: Re: something I found for sale on the web Are you buying this guys pitch? Post by: KB3DKS on April 11, 2009, 02:57:57 AM 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 Title: Re: something I found for sale on the web Are you buying this guys pitch? Post by: K1ZJH on April 11, 2009, 08:23:57 AM 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 Title: Re: something I found for sale on the web Are you buying this guys pitch? Post by: KB3DKS on April 11, 2009, 12:57:19 PM 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 Title: Re: something I found for sale on the web Are you buying this guys pitch? Post by: AB2EZ on April 12, 2009, 07:35:54 AM 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 Title: Re: something I found for sale on the web Are you buying this guys pitch? Post by: k4kyv on April 14, 2009, 01:40:16 PM Maybe someone cut off the pins in hopes of salvaging some oxygen-free copper. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
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