John wrote:

Here is a drawing of it: http://www.digoliardi.net/electrics2.gif

I am dangerously ignorant of electrics so I'm asking: How does it work
that one AC pole goes to one pole of the orange thing (capacitor?) and
then also go around it? It's there a short there?

The electro magnet works just fine. Nothing gets hot even with a long
'on' time (for focusing). Do you think it is safe to hook up to the
timer (F-Stop timer by Darkroom Automation)?
_____
The circuit diagram looks correct. It is a half wave rectifier with an
80 microFarad storage capacitor. The capacitor is always kept charged
through the 200 Ohm resistor by the silicon diode (TR210). When the
switch to the solenoid is open, the DC voltage across the capacitor will
be about 169V (square root of 2 times 120V). When the switch to the
solenoid is closed, DC current will flow through the magnetising coil,
thereby opening the shutter. The actual voltage seen by the solenoid
coil will be lower than 169V because of a small drop across the 200 Ohm
resistor. The drop depends on how much current the coil requires. The
capacitor could be of a higher voltage rating to be safer. If the
solenoid "hums" due to the half wave nature of the circuit, you could
increase the size of the capacitor to, say, 150 microFarad, or use a
full wave rectifier. You should put a master power switch on the hot
side of the the AC line (black wire in USA/Canada). It would be no
problem plugging this device into a timer since the current draw will be
in the order of 250 mA (my guess).
--
Regards / JCH