Creating new electronics for Super Graphic?

Discussion in 'Large Format' started by henry_finley|1, Dec 12, 2017.

  1. I've given a lot of thought about the 45V system originally installed in the Super Graphics. The one question is why they went to the 2-22½ battery arrangement, when the Speeds had the low voltage solenoid that obviously worked. I understand why they did it, but now 60 years later it's a mess. And here's where my lack of electronic circuit design knowledge leaves me able to dream up the concept of the wheel, but no ability to actually design it. Here's what I know: The battery bay on a Super could hold 4-AAA batteries in an easily fabricated pack.
    Certainly in this day of modern electronics there must a circuit design to kick that 6V up to the needed voltage to trip the shutter with the pre-existing lensboard solenoid. And this circuit should be able to be contained in the same space after removal of the camera body's factory capacitors and diodes and such. A further advantage being that it would be a true open circuit when the red button is not depressed, rather than depending on capacitors not leaking and running down the expensive batteries when the camera is not being used.
    I do not know what the voltage at the solenoid contacts was with the original wiring, but certainly there must be a way to do this, if anybody knows anything about designing such a circuit.
     
  2. I have a USB (5v) powered audio mixer that supplies 48v phantom power for condenser microphones. So, yes, it's perfectly possible to design an 'inverter' or step-up circuit.

    However, the current available from a small inverter running off triple-A batteries is going to be limited - a few milliamps or so. Therefore the large capacitors will still be necessary to deliver enough 'kick' to the solenoid.

    The battery drain can easily be fixed with a simple on/off switch though.
     
  3. Thank you for answering. I had hoped to think there was a way to come up with a circuit (which I have no electronic knowledge to design) that would be "always off" until the red button on the camera was pressed. Single phase capacitor start, capacitor run electric motors can "kick" instantly, so why not my idea, I thought. As I understand the Super Graphic, there is no on-off switch for the battery-capacitor circuit. But batteries are protected from being under constant drain only due to good capacitors being in the circuit.But once capacitors get old and leaky, a 40 dollar set of new custom-sold batteries would get drained down in no time, if I were to buy some and install them in my Graphic with its 60 year old capacitors.I have no intention of installing and removing batteries incessantly just to protect my 40-50 dollars worth of batteries. and AAA alkalines are dirt cheap at the Family Dollar. So... how about two 9 volt cells. They would fit, and that's 18V instead of 6 with the 4 AAA's. That's closer to 45V. Even though 9V batteries aren't cheap, but at least they are common, and don't cost $20-30 apiece like the 22 1/2V special order cells.
    I have never seen a thread on any of these photo sites where somebody brought up this Super Graphic issue in the depth I am now attempting. OK, so my idea would require a switch, perhaps set in a custom fabricated battery bay cover, which a lot of these cameras are missing already. And said switch would have to be flipped in anticipation of taking a photo, and flipped off again later. But not immediately, necessarily. So obviously you couldn't walk around blissful that the red thumb button on the camera will "kick" your solenoid on demand. But certainly I must be on the right track with my idea. An idea BTW, which MUST NOT involve destructive modification of the camera irreversibly.
    I want my red thumb button to work, and I don't want to buy special order 22 1/2 V batteries, and I don't want holes drilled by knuckleheads in my camera installing hairbrain homemade ideas.
     
  4. The issue is that the solenoid needs tens or hundreds of milliamps momentarily to drive it. That's delivered by the storage capacitor(s). However, since the battery circuit can only supply a small current, it takes time to charge those capacitors.
    Expecting the solenoid to fire instantly from 'cold' is unrealistic. It would draw too much current from the inverter circuit.

    Having a pre-charge 'on' switch is the only way I can see around it. Not unless you change the solenoid for a low voltage one and fit higher power batteries - like rechargeable AA cells.
     
  5. What about replacing the capacitors with new ones?
     
  6. Replacing with new capacitors would be a poor idea, considering the likely usage frequency in this day and time. Capacitors leak down. With no switch, and the capacitor being your "switch", you essentially have a circuit that is always on and draining batteries, though more slowly. But still draining.
    In 1957 when it was a daily use camera, and new batteries available at every drugstore at cheap prices, it was one thing. The chances of the batteries being used up long before they leaked down from infrequent use, made the circuit perfectly economical in it's day. Now, you can spend $40 for new batteries, use the camera once a month, or twice a year, and have to re-buy batteries each time you wanted to use it.
    I understand this site has a limited readership, and my answer may lie with someone who has never visited the forum. But I have no doubt somebody somewhere can design a replacement circuit that will fit in the same place, without altering the camera with drillholes that detract from the camera's original condition and saleability.
    We're only talking about tripping a solenoid. The Pacemakers tripped solenoids with 6 or less volts. The photoflash batteries were its capacitor.
     
    Last edited: Jan 18, 2018 at 11:42 PM
  7. Hi,

    I'll chip in and ask what the solenoid was for ... I'm assuming shutter ? I do not own a Speed Graphic nor have I ever seen one. I do own a lot of large format gear otherwise.

    I'll help you if I can for the design. Email me or PM me.

    As far as you know, what were the original circuit components ? A battery, a capacitor, a switch and a solenoid ?? How much room do we have ? Four Eneloop AA NiMH batteries will give a lot of grunt...
     
  8. Back in the days before in-shutter flash sync, the solenoid was used for that purpose. They're a less than perfect solution, but work well enough. One advantage is that you can also fine-tune the delay between pressing the button and the shutter firing to make sure you're getting the peak output from the bulb.

    Graflex flash guns usually have a button on the back-you press this to trigger the bulb and flash gun both.

    BTW, Graflex flash guns usually use D cell batteries, and I've been warned to never use less than a 3 cell gun(or 2 cell with an extension) to attempt to trigger the solenoid.
     
  9. So Ben, the 'button' is pressed to release the shutter manually and also to fire a solenoid that trips a flash ? Can I also assume the batteries for the setup also power the flash ?? My mind is wandering here ... the 'flash' is a high-powered incandescent bulb ??

    This is getting fairly zany / crazy .... !!

    I think I need a diagram.
     
  10. The Super Graphic has a couple of ways to operate. The way that Ben is speaking of uses a small button on the camera body to trip the shutter (via a solenoid) - this is independent of a flash gun. This is where the special batteries are required.

    If you are using a flashgun, there is a special cable connecting the flash gun to the camera body. As I recall, you could then fire the shutter AND flasbulb using either the button on the flashgun OR the button on camera body.
     
  11. The flash in this case is a flashbulb. Flash bulbs are a topic in an of themselves, but a "typical" flash bulb from the era we're talking about is a a glass envelope filled with magnesium "wool" in a 100% oxygen atmosphere. Apply power to the bulb(usually a few volts and not much current) heats up an igniter that "lights" the magnesium wool, and it rapidly burns.

    The bulb takes a bit of time to reach its full output, and on a camera with an M-sync setting the flash is tripped a few milliseconds to allow the bulb to light up fully before opening the shutter. As a side note, there are special "focal plane" bulbs that are designed to reach their peak output quickly(~5ms for a GE #6) and burn for a long time(~1/30 again for a GE #6). I use #6s with my Nikon Fs, although I don't think they're suitable for the focal plane shutter on a Speed Graphic as they don't burn long enough.

    The delay is also partially where the solenoid comes into play-when you press the button on the flash gun, the bulb is fired immediately but it take several milliseconds for the solenoid to move to trip the shutter. There's a micrometric adjustment on the solenoid to allow you to fine tune how long the delay is. I'll also add that the solenoid isn't a Graflex-only thing-I have a Rolleiflex Automat III that doesn't have flash sync, but was adapted with the hardware to fit a solenoid. It doesn't HAVE one, but one could easily be fitted(it has lugs on the body to mount it and an "arm" that trips the shutter and wouldn't normally be present to connect to the solenoid).

    Flashbulbs throw a LOT of light for their size-significantly more than an electronic flash. One of my favorite photographers-O. Winston Link-used an array of 50-100 bulbs to illuminate trains at night.

    I would say that the stereotypical Graphic flash bulb is the GE #11, which is a screw base bulb about the size of an appliance lightbulb. For cost and practical reasons, I usually use a GE #5 or Sylvania P25(more or less equivalent) in mine(I use this bulb same bulb in 35mm and MF applications). These bulbs are about the size of a walnut, have a bayonet base, and throw ~1 stop less light. The GE #6 I mentioned earlier is the same size and actually has the same total light output-it just doesn't "peak" like the #5/P25.
     
  12. I am not familiar with the camera but I search online it seems that the battery is needed to trip the shutter not only to fire the flash.
    As far as making something to supply higher voltage from a low voltage that's possible but I wouldn't go that route. I would look for the high voltage battery or assemble one with sufficient voltage.
     
  13. 22.5v x 2 = 45v = 9v x 5
    You could make a small box to hold five 9v batteries, then attach that box to the camera.
    Kudgy, but it will do the job for cheaper than $40-50 in 22.5v batteries.
     

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