Super Graphic Electronics Question

 

Super Graphic no, Super SPEED Graphic si.

 

Yep, I just didn't have the energy to respond. Ed also leads one to think that the Super Graphic cannot use the flash gun button to trip the shutter - it can.

There was no focal plane shutter in the Super Speed Graphic, just the high speed lens shutter. There is a two-pronged connector on the lens which can be connected to a Graflex flash gun, which can then be used to fire the solenoid.

 

That shutter was special. In order to achieve 1/1000, the blades rotated 360 degrees rather than reversing direction.

The Super Graphic did not have that high speed shutter.

Here is the circuit. The more posts I read, the more confused I get. I'm a radio man KN4SMF, and you would think I would have brains enough to understand this circuit. But I don't. For one thing, we're dealing with 45 volts worth of batteries. But look at that resistor. That would almost cause me to believe the solenoid itself is not a 45V solenoid, but something far less. Now post 24 above tells me that the solenoid has no need of capacitors to "kick "it. THAT'S what I always thought. i don't know of any solenoid I ever saw to need capacitors to fire it. The more I look at this the confuser I get. I can't even figure out which legs of A, B, and C to go the flash. In my case a Honeywell Strobonar 682S.

 

A is the ground. B shorted to A fires the solenoid. C is the external flash contact, referenced to A, the ground.

 

The 80 mfd capacitors provide impulse power to fire the solenoid. The 2.7K resister limits the current draw to recharge the capacitors after firing. The diode supresses the reverse voltage spike due to inductance of the solenoid.

Thank you Ed. That was very clear and now I'm happy. It was just about the way I was figuring it (for the most part). So all I really have to do is get some fresh new high quality caps in there to cut out the fear of leaky old ones bleeding down my batteries.

Solenoids have a lot of inductance. The way to get them to fire faster is higher voltage. My guess is that's the reason for charging up the caps and using them for the high current pulse that the battery alone couldn't do. Also, applying direct battery voltage for any length of time might overheat the solenoid.

The solenoid will have a direct battery connection as long as the switch is closed, in series with the 2.7K resistor.

True, but it won't hurt anything other than running the battery down if for some reason the switch remained closed.

Cowboy, please read post #18 above. In it I name the batteries required and point out that they can still be purchased. No need to improvise ...

Yes, and the OP was already aware of that fact. However, the brief, as I understand is; to use more readily-available batteries at a lower cost. Those #23A 12v batteries would seem to fulfil that brief almost perfectly.

 

The Ever-Ready 412 equivalent seems to cost in the region of $10 each, and has to be ordered by post. Whereas 4x #23A batteries cost around $2 for all four, and can be picked up at almost any general or hardware store.

 

At least now we know exactly what the circuit is, and the capacitor values. A single 120 to 150uF 63vw capacitor should be easy to source, and will be about the size of a pencil top eraser. No size issue replacing the original capacitor pair there, I suspect.

 

So the only 'modification' needed is to get 4x #23A (or the slimmer #27A) batteries into the original holders. This might be done by dismantling a pair of used 22.5v batteries and using the connector plates from them as part of a fabricated holder for the #23As.

 

The difference between having 45v and 48v supplying the solenoid capacitor(s) will amount to no more than a 14% increase in energy. This is insignificant compared to the standard +50/-20% value tolerance of electrolytic capacitors.

P.S. the diode is what's called a 'snubber'. It's there to absorb the back EMF from the solenoid inductance, which might otherwise puncture the insulation of the capacitors, or burn the switch contacts.

 

And just to further clarify:

Contact A is a permanent connection to the solenoid.

Contact B is an auxillary remote firing for the solenoid/shutter, by connection to A.

Contact C goes to the flash.

Edited June 2, 2020 by rodeo_joe|1