So what do you do with an old flash with no manual power control? You modify it of course.Not such a big deal if the flash in question has an Auto mode sensor, just replace the sensor with a logrithmic pot. But if it is a TTL only flash then you have a lot more work.
In 1990 Canon released a small hotshoe mount flash the 200E. As bare bones as you can get. Controlled by A-TTL only.
It has a power switch to turn it on and a ready light to tell you when it was (you guessed it) ready to fire. Nothing else for controls. It doesn't even have a test button.
While it can be used on an old A-TTL film camera but it is next to useless for off camera work. So I changed by adding manual power control, adding a test button, and an optical slave circuit. Still to come is a 1/8" jacj so it can be triggered by an RF or external optical trigger. As soon as I decide where to put it.
The top image is the front view of a modified Canon 200E flash. The focus assist light was removed and a solar cell used for optical triggering (and other parts) were added. The small yellow pin on the lower left is the new test switch.
