[ARC5] Why "Noodling" About Sweep Tubes

[Fuqua, Bill L]

  The 807, 1625 and 6146 all have beam forming plates connected to cathode. There were makes of
1625 tubes that had separate wires for cathode and beam forming plates which went to a common pin.
Hams would either remove the bases move one to  a separate pin and re-glue the bases or drill a hole
in the side of the base and reach in to make the modification. This was done for the LA-400 linear amplifier.
At that time the 1625 tubes were available at 5/$1.00.

Some, not all, horizontal tubes are this way also. However, the prized ones are the
ones that can be put into grounded grid operation such as 6JE6 and 6LQ6 and these are
prized by the CBers, thus if used they are used up or if new expensive.
  Since horizontal output tubes were not intended for parallel operation there were no
attempts to make the specs tight enough so that they would be fairly closely matched.
  The 4- tubes are tetrodes and the 4E27A is a pentode with a separate pin for the 
suppressor grid. However, as I said they actually are very cheap on the E)(#* site, just 
search and click on sold items in the left column to see what they actually go for. There are a number
that are listed for much higher prices. 

73
Bill wa4lav


________________________________________
From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on behalf of Ian Wilson [ianmwilson73 at gmail.com]
Sent: Wednesday, October 23, 2013 7:37 PM
To: Kenneth G Gordon
Cc: ARC5
Subject: Re: [ARC5] Why "Noodling" About Sweep Tubes

"Although they are 'beam tubes' their advantage over other types of beam
tubes is that their beam-forming plates are connected to separate pins, and
not to the cathode, as all octal-based beam-tubes are."

Not sure about this: the 4-125A is a tetrode, and the 4E27 can manage
suppressor grid modulation, which would seem to suggest more of a
traditional g3?

73, ian K3IMW


On Tue, Oct 22, 2013 at 2:13 PM, Kenneth G. Gordon
<kgordon2006 at frontier.com> wrote:
> Bill is certainly right about the 4E27 and the 4-125 and its pulse variants. I
> had forgotten about those. Either would be perfect for your uses, and both
> are cheap on eBay, especially the pulse variants which are not as easily
> recognized.
>
> There was a later variant of the 4E27: the 5-125B/4E27A. Those often show
> up too, but sell for higher prices.
>
> The PD of the 4E27 is 75 watts, while that of the 4E27A is 125 watts.
>
>
> Either one uses an 813 socket.
>
> Although they are "beam tubes" their advantage over other types of beam
> tubes is that their beam-forming plates are connected to separate pins, and
> not to the cathode, as all octal-based beam-tubes are.
>
> Ken W7EKB
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