[volt-nuts] Finally got around to modifying my Fluke 845ab with LED's

NeonJohn jgd at neon-john.com
Tue Sep 9 21:15:27 EDT 2014

On 09/09/2014 09:00 PM, Brooke Clarke wrote:
> Hi Chuck:
> Is there something special about the GR strobe tube that prevents you
> from using a more modern strobe tube?

Extremely special.  Google "GR guided arc flash tube".  There are some
old GR tech reports on the tube.

It uses a large bulb so it won't melt at very high flash rates and uses
a series of electrodes between the main ones, biased like in a
photomultiplier tube, to keep the arc nice and tight.  It quenches so
fast that the xenon afterglow is the main thing that limits its flash rate.

I have two of the earlier GR neon tube based Strobotrons.  The neon
actually has less afterglow than xenon but they hadn't discovered the
guided arc principle yet so it isn't as bright.  But it's real fast.  In
one of them I replaced the tube oscillator with a little microprocessor
board to give it crystal-controlled accuracy.  I retained the cool
multi-turn analog speed control to keep it looking authentic.
Linearizing that thing in software was a chore!


John DeArmond
Tellico Plains, Occupied TN
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