It has been a long time since I experimented with xenon flash circuts so I needed some review. I found this site ( which has a schematic ( for a high speed Edgerton flash and a description of how it works.

Page 7 of this PDF ( shows and explains a circut that more closely matches that in the EG&G sensitometer.

Inspection of the EG&G sensitometer circut reveals mostly common compononts such as resistors, capacitors, chokes, switches and a power supply. There are two fancy coils, one is the ignitor coil and the other is some kind of 'in house' (stamped EG&G) coil that goes between the ground and the 'high speed' large discharge capacitor.

The mains are connected to a special "regulated" power supply. This is a metal box with a fancy transformer on top and some hidden components underneath. There is a metal access door to the underneath components and it looks like there is a big capacitor can in there (perhaps a filter capacitor, however, I think the output is AC, not DC) I know for shure there is NOT a silicon/IC controlled voltage stabilization circut in there. Probably some clever analog circutry that would be rapairable if broken.

The lines from the power supply go through the bottom of the chassis and travel to the main circut board. This is a great board, there are just posts and wires, NO traces. Very elegant. (the inner workings of this machine belong in a MUSEUM!)

The bottom of the circut board has 6 blue chokes (or they look like chokes). They are arranged in a pattern that reminds me of a transformer schematic, with a central tap. This central wire leads to the top of the board. I suspect this is the voltage multiplier circut. I also suspect the power supply that feeds this is an AC supply.

From here it looks like things get split up in to charging circuts for 4 capcitors.

1) The '10-2' capacitor, which is a shiny aluminum cylinder.
2) The '10-3' capacitor, which looks identical to above.
3) The '10-4' capacitor, which is the large oblong capacitor on the right of the chassis.
4) The small axial capacitor for the ignitor circut

(If you are confused, '10-2' is an abbreviation for scientific notation and implies "1 times 10 to the negative 2" or 1/100 of a second)

The above mentioned PDF describes high speed capacitors as needing low internal resistance.
This is a quote from (
"...capacitors of extraordinarily low internal inductance .... Such capacitors are made by interleaving sheets of conducting foil with sheets of insulation and connecting the many alternate conducting sheets at the edges. The fabrication technique is costly, and the capacitors are also expensive"

My intuition would say that the shorter duration flash circut (10-4) would be the smallest capacitor, however, it is in fact the largest on the chassis. My impression is that the capacitor is a special 'high speed' capacitor, as described above.

The other two capacitors look like standard 'can' capacitors.