Bronica EC Shutter problem

Discussion in 'Medium Format' started by halvor_sens, Oct 14, 2015.

  1. Hello,
    I have a Bronica EC 6x6 camera with a problem.
    The mirror goes up and the shutter opens, but they both do not go back in their original position. Battery is new.
    In fact it looks like the timer does not give a signal to “close” after the exposure. Putting the speed to “B” brings down the mirror and closes the shutter again.
    I checked the wiring and all the contacts, but I suspect an electronic component PST 090. I tried to exchange some condensators, but no result.
    Does somebody knows this problem or has another suggestion?
    I would like to repair this beautiful tank!
    Thanks a lot for your answer!
  2. Repair/parts options are near zero. Live with the problem and the "B" solution. Otherwise, look for a mechanical Bronica(S2, S2a), especially if you have Nikkor lenses you like. Frankly, like all FP shutter Bronicas, it's a relic. If you like SLR 6x6, look into the later SQ series.
  3. For old Bronica repairs try:
    Camera Wiz

    Mr. Frank Marshman

    1495 Needmore Lane, Harrisonburg, VA 22802


    KOH's *used* to repair Bronica cameras. They might have parts or know what is wrong with your camera.

    Koh's Camera
    2662 Jerusalem Avenue
    North Bellmore, NY 11710

    Good luck!
    cameragary likes this.
  4. I realize this note is a bit late in coming, but just for a bit of perspective, I visited eBay and searched for Bronica EC. There's a body only -- well worn but guaranteed to work -- for $92. I'm sure this is cheaper than any repair you'll be able to find. ECs with lenses on eBay begin at about $250 and go up from there. It's a camera that's held is value better than a lot of other medium format cameras. I used to own an EC-TL and I loved it. Sold my sizable EC-TL outfit to buy a computer. What a mistake. I still miss it and that was years ago.
  5. Hi.
    Fantastic news! I managed to repair my old Bronica EC.
    A small electronic print with the "timer" (PST 090) on it was not functioning.
    This part is not available anymore, so with the help of another electronic circuit forum, I built a small circuit based on a NE555 chip.
    It looks like this works. I am trying my first film now!
    Happy to share the design; parts are cheap; less than 2 euro.
  6. Here is a picture of the repaired Bronica EC.
  7. Hello,
    I have a Bronica EC with exactly the same problem. Could you please tell me if your circuit worked alright? I hope you still follow this thread.
  8. Yes Vaidotas,
    I made a lot of pictures since the repair and everything works!
    The new little electronic circuit does the same as the old one and costs only a few Euro.
    Happy to help you!
    Where are you from?
  9. Thank you for the answer!
    I'll try to make one myself and to figure out where to connect each cable. Previously I just soldered new electric guitar pickups, let's see if can get right parts and assemble it right.
    Is the shutter timing correct? There seems to be a variable resistance on the old circuit, that was probably for adjustment?

    I live in Luxembourg
  10. Great.
    If you have any problems, just let me know.
    I might have most of the parts as spares, so if you can't find them let me know. They cost a few cents...
    Can you send me a picture of the inside of your EC? Is it exactly the same as mine?
    I can send you the cable connections (colors) I used in my EC , if you want.
    There is no further adjustment needed, because the C and R's are well dimensioned. I tested some longer timings and they were spot on!
    Good luck and let me know if it works.
    By the way, the problem is not in your battery connections or so? Does the little green lamp glow if you push the button?
  11. I ordered the parts I'll see if it works. Yes, it would be nice to know the colors for the connections.

    Sometimes I buy broken cameras (mechanical) and I make them functioning again. I got this camera very cheap. The buyer told it was "working", but in fact, as I suspected for the price, it was not. Just the B setting was functional. And indeed at the beginning it was a battery connections' oxidation problem. There was no green light. I cleaned the connections and the camera was functioning allright. I just loved the images the 75mm lens produced, comparable to Hasselblad's 80mm Planar, but maybe even more pleasant.
    Then after three weeks it started to be erratic. Sometimes it did not react any more: it was working after staying without a battery for a few hours. After some time it was all over. The green light is on. I took off the covers from both sides, but did not find any loose or damaged cables or anything else strange. So right now I can only suspect the electronics. I'll see if your circuit helps.
  12. I added the circuit with the colors of the wiring.
    In fact you only have 4 wires to connect.
    The wire between the variable R to +6V is in the camera as is the wire between the electromagnet and the ground.
    1. Yellow comes from the Var. Resistance (shutter speed selector) and goes to pin 6 and 7 of the chip.
    2. Orange is the contact that gives +6V as soon as you fire the shutter; it stays under tension until the cycle closes. Is goes on pin 4 and 5 and R1 and R2 and (already in place) on R3 (shutter speed)
    3. Black is the ground and is on pin 1 and the minus of the Elco C1.
    4. Brown is on one of the poles of the electro magnet and the diode. It goes to pin 3.
    You can download simulation software called LT Spice from "Linear Technology" (free software) to see what happens if you change R3 (shutter speed resistance). You will see that the shutter speed varies just like it should in the simulation.
    Use the Bronica4.asc file to do the simulation. In stead of the electromagnet it contains a LED and R7 for the correct simulation.
    Good luck and let me know if it works. I included some more pictures.
  13. Simulation file cannot be added here.
    I could send it by mail.
  14. EC with old circuit.
  15. Bronica with new circuit.
  16. New circuit in place.
    mag_miksch likes this.
  17. Hi,
    I have a EC with the same problems.
    cannot be added here.
    Could you send me the simulation file by mail?
    Thanks a lot.
  18. paul ron

    paul ron NYC

    NIce repair and detective work.

    Post your circuit diagram?

    So the 555 timer is a one shot in conjunction with the speed resistor chosen? The resistors that govern the speed gets inserted into your circuit, I guess, and make the correct time outs.

    NICE! Very clever solution.
  19. Me too. My EC has the same issue. I have figured out the basic circuit, but I have questions. I could use clarification of the wiring in the camera. Also, the circuit I came up with has the problem that, although it times the "shutter" (an LED), it only does so if the switch is released BEFORE the end of the time period. Might be difficult with fast shutter speeds. It appears that, with my circuit, the standard monostable circuit for the 555 chip, the shutter will remain open as long as the shutter button is held down. Unless the shutter switch in the camera somehow solves this problem. Can anyone help me?
  20. Sorry to be a little late Richard, but you still have the same problem?

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