Peufeu's Electronic Stuff Unfinished projects since 1912

I got this big Sunpak on ebay. The synchro plug has 200V on it ! There is no way I'll connect my camera to this thing.
So I needed a slave flash trigger. The Net only yielded 20 years old schematics with obsolete parts that are impossible to find.

So here we go :

Basically it's a third order highpass filter followed by a comparator transistor. It works very well, is quite sensitive, and doesn't trigger when it doesn't have to.

- The BPW50 PIN photodiode is the one the electronics store closest to my place had in stock
- There is no thyristor. There is a thyristor already in the flash, besides I couldn't find one in the store and they were closing. BF469 is rated at 250V. It works.

Schematics :

Result :