All good points Roger and right on the button.
I don't have a 6993, but do have a 719, which looks the same but is 2 or more times longer.
Will try it today If possible, otherwise tomorrow for sure.
You're right we don't know everything there is to know, but that is probably because of trade secrets or whatever else (greed?).
Anyhow we do know from radio tubes that gas filled regulator tubes come in many different HV's and fill gasses (and therefore colors of glow), all no doubt carefully researched for the particular needed product by selecting gas type, mixtures of gases maybe, and certainly pressure of the gas.
Geo
?
----- Original Message -----
From: Roger Whatley <rogwhat53@...>
To:
[email protected]Sent: Mon, 04 Apr 2022 16:58:29 -0400 (EDT)
Subject: Re: [CDV700CLUB] Question and an interesting site for those that modify CDV700s and more.
Geo,
I would look forward to the same measurement
but taken on a 6993 operating at 900V.
Maybe operates different from the Russkie's
tube, or maybe not.....
I totally agree,wrt similarity of your result
~50V and Neon bulb..... I assume that Russian tube is a neon
tube..... but 450V-50V = 400V is a long ways to slew in a
(hopefully) short time. Depending on total parasitic capacitance
(cabling, etc) the time it might take to do that would limit
pulse rate quite a bit; I would think it would saturate at a
relatively low count rate.... And maybe the 6993 is designed to
improve on that???? I don't know.... I may look for some more datasheets for
comparison.
I definitely don't understand everything I
know at this point.
rogerw
?
On 4/4/2022 1:01 PM, Geo Dowell wrote:
Ah good. Somehow this important Topic got?"locked" last night.
If a moderator did that please let me know. It's unlocked again.
Here's the latest and more critical look at the Bias HV drop
across the SBM-20 GM tube operated at 450V via a re-regulator
base from 920V DC from a Ludlum Bench "Geiger Counter".
First the last night report- updated?
"While attempting to clean up the workbench today, I had to look
into this. Using a Russian SBM-20 (because it was on the
workbench for a different project) and one of my 900 to 450V
adaptor bases, scope attached directly across the GM tube (scope
rated for 2000V), and a mantle for a source, the peaks on the
scope showed negative pulses measuring f 450V P-P. At the
"Geiger Counter" actually a (Ludlum 2500 Bench scaler) the P-P
was 900V."
Looking again this morning with caffeinated eyeballs, a
selection of eyeglass and more patience. Specifically looking to
see if the "valley" goes all the way to zero before resetting.
Best I can tell it does not go to zero, but the exact floor is
difficult to determine with this 'scope, it seems to be
somewhere around or just above 50V above ground. This would
track very well with the NE-2 Neon Bulb analogy.? Someday (not
this day for sure), we'll nail that down, with the storage
'scope, or someone else can.
By the way a GM tube activates with radiation because it is
being operated on the knee of the gas discharge tube curve, in
the Geiger region, and there is always a wide latitude of exact
HV settings that allow that proper operation. + or - 50V or even
more is normal, and is what Rad Techs call the "plateau" area
(flat spot) of the curve.
Back to the discussion guys, sorry for the unintentional
temporary lockout of us all.
Geo
--
rogerw
On the Catclaw
¦¬¦¯¦«¦¸¦ ¦«¦¡¦¢¦¥
The PanDemic is over, but the DemPanic goes on.
MisDisMal is a dictator's tool of repression.
