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Re: Tube coils for beginers 2
On Thu, 23 Jan 1997 23:07:08 -0700 Tesla List <tesla-at-poodle.pupman-dot-com>
writes:
>Subscriber: dwt-at-efn-dot-org Thu Jan 23 23:06:36 1997
>Date: Thu, 23 Jan 1997 22:07:06 -0800
>From: David Trimmell <dwt-at-efn-dot-org>
>To: tesla-at-pupman-dot-com
>Subject: Tube coils for beginers 2
>
>Hello again,
>
>I have recieved e-mail from my uncle who is a manager/radio engineer
>type and he replyed..
>
>"These are pretty old tubes, and I don't know if any stations are
>still
>using them. Probably, but I don't know which ones. Could you use
>pentodes like a 4cx250B or similar. These are more easily available,
>but require air cooling."
>
>So what about it? The 4cx250B's I should be able to get used ones for
>next to nothing. Again I am a beginer in this tube buisness, so be
>patient if I am asking stupid questions.
>
>Thanks again,
>
>David Trimmell <dwt-at-efn-dot-org>
>
>PS-- I have also an interest in X-Ray generation and if anyone knows
>of
>any particular types of tubes that may be able to be pushed to produce
>them please let me know (Please contact me via private e-mail, as to
>not burden Chip with off topic stuff) Yes I know the safety stuff as I
>have worked as a Radiation Safety tech.
>
David a 4cx250 will work, but DON'T take the usual route with this
tube and tie the screen and control grids
together to simulate a triode, if you try to run it this
way you stand a VERY GOOD chance on distroying the tube.
This tube must be run as a tetrode with voltage on the
screen, you could run the screen and control grids tied
together via a capacitor for a common RF connection but
not common for AC/DC potential because the screen under
these conditions will draw excessive current as its
Mu factor is much higher than the control grid.
The 813, 803, 4-1000, 4-125 thru 4-500 tubes can be run
in the triode connection safely.
Good triode tubes are: 811A, 572B, 3-400, 3-500, 3-1000,
833 etc.
Mark Graalman (WB8JKR) TCBA#1399