Ghetto Monolight, Part I

My little experiment with the basket of teeny tiny flashes hasn't worked out. It's impossible to trigger all the flashes using a single trigger circuit (only one or two of the flashes fire). I don't feel motivated to assemble ten trigger circuits worth $3 each (and my labor) to fire tiny GN 7 flashes that cost $0.80 each.

What I've decided to do is use the trigger transformers and U-shaped flash tubes that I bought with the basket of tiny flashes, and make my own (full-power) monolights, using the huge capacitors from the non-working Vivitar 283 hot shoe flashes.

First step is to build a high-voltage power supply.

I used the "Super Simple Inverter" design from Sam's Strobe FAQ Components by Sam Goldwasser.

I made a few minor changes to the design: I substituted an MJE3055T for the 2N3055 in the design (TO-3 transistors are just so bulky).

And since Alexan Commercial was incredibly, out of 1 uF capacitors when I visited last week, I changed the timing circuit from a 1 uF / 4.7K combination, to a 2.2 uF / 2.2K combination. RC time constant is pretty much the same. I used the smallest 220V to 6-0-6 V transformer that Alexan had.



Prototyped it on a breadboard, got about 250V on the output of the transformer when powering it off a 6V gel cell, not too shabby:



I then built one copy on a piece of veroboard. I'll build the other one tomorrow night when I have more copious free time.



Next step, building the trigger circuit to produce the 4000V pulses to fire the flash. Coming soon!