According to Joseph Gwinn :
The EG&G FX-6A xenon flashtube is used in the General radio Strobotac,
which is used to measure the speed of machines rotating at up to 25,000
rpm.

The FX-6As darken with age, and are hard to find.

FX-6A is an old EG&G product. The relevant part of EG&G was sold to
Perkin-Elmer (http://optoelectronics.perkinelmer.com), and P-E now makes
these flashlamps. I think that this is still done in Salem, Mass.

Hmm ... where my wife was born (though not in the P-E plant. :-)

I talked to P-E today. The FX-6A is available for US $232.00 each for 1
to 10 units. FX-6 series are called "low cost strobes"; I don't want to
know what normal and high cost means.

####### ###
# # # # #### # # ###
# # # # # # # # ###
# # # # # ###### #
# # # # # # #
# # # # # # # # ###
####### #### #### # # ###

(The above should be viewed with a fixed-pitch font like Courier. If
you don't want to take the time to switch fonts, it simply says "Ouch!"
in *big* letters. :-)

That means that the batch of four which I won on an eBay auction
is worth $928.00.

They were made May 22 1975 according to the stamp on the box
endflap.

They also sent me a FX-6A datasheet (well, max operating conditions):

Max energy per flash: 5 Joules.

Max average power: 7 watts.

Max anode voltage: 1000 Vdc.

Min anode voltage: 300 Vdc. (Typical will be ~600 Vdc.)

Max flash rate: 500 flashes per second (30,000 rpm).

O.K. Which probably determines the choice of max RPM on the
Strobotac.

Arc length is 7.9 mm. The trigger electrode (called the "sparker" is
near to the anode and cathode, inside the glass envelope.

Actually -- there are five of them, One (pin 1) is very close to
one electrode (pin 9), and the remaining ones are equally spaced, with
the final one not being nearly as close to its electrode.

But this suggests that they fire at much lower voltages than the
typical trigger wrapped around the outside of the typical flashlamp.

The required
voltage and energy was not documented.

Hmm ... A pity that it is not documented. That could be one of
the factors which would make a normal flashlamp not suitable for the
circuit in the Strobotac.

Thanks for digging up this information.

If nothing else, it makes me feel better about spending a bit
over $125.00 for the batch of four of them -- and now I understand the
motivation of the winning bidder in the batch which I *lost* prior to
that. :-)

Enjoy,
DoN.
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