Sticky: Recent Updates and Important Information

Sticky: Recent Updates and Important Information

Tuesday, March 19, 2013

Adding flash capability to Duo

Due to the number of requests, today I looked into adding flash capabilities to Duo - and it turns out it's a pretty simple affair. If you watched the video on separating the 105mm lens pairs, you'll see that the PC socket gets detached. Here, I reattach the PC socket and ground it to the lens to complete the flash circuit. Click through for the full write-up!

First, a brief overview. The PC socket works by triggering the flash when a circuit in the lens closes. For the Mamiya 105's, the center contact of the PC socket attaches to the contact in the lens, and the outer contact is the ground. The original Mamiya lens board is metal, so the socket is grounded to the lens by direct contact to the lens. However, Duo is all wood, so we need to add a ground contact to the lens. The lenses come with a small metal leaf-spring that contacts the conductive aperture ring on the base of the lens.

My apologies that I didn't take a lot of photos while soldering stuff together.

Here we've resoldered the PC socket to the wire from the shutter. I've also soldered a wire between the contact spring and the outer ring of the PC socket.

Here we can see the outer and inner contacts: inner contact to the lens wire, and outer contact to the ground wire.

The leaf spring gets glued to the lens board, so that it will contact the aperture ring. I glued a small piece of hard wire to the PC socket to fix it to the front standard.

Then we screw the lens back in. Piece of cake!

For anybody wondering what the spring is doing attached to the shutter cocking lever, it's just some extra encouragement to open the shutter when it's fired - my particular shutter is a little gummy.

Now to test the circuit. When the shutter is closed, the multimeter registers an open circuit. . . 

. . . and when we open the shutter up to "B", the multimeter sees that the circuit is closed, and it emits a tone. 

Success! Somehow, I don't own a female-female PC cord, so I had to kludge together some wiring to hook it up to my wireless flash triggers (the el cheap-o eBay type), to fire a 285HV. Works like a charm, though.


  1. thanks kevin! that's exactly what i was looking for...

    2 more questions/things

    - would it be possible to post a tools/materials list for the build?
    - how can the non-deluxe camera kids get that snazzy metal hardware upgrade?

    1. Im with Steve, it would be nice for the longevity of e camera to get metal parts, if you cant provide them could you point us in the direction of who can?

      Also how are things going? Would you let us know?

    2. This comment kind of got swept under the rug, so sorry about the late reply! Yes, I can have a tools/materials list up in a few hours. And with that post I can also include links to the metal hardware.

      Concerning the metal hardware, it's just labor intensive to ream the bore to the correct diameter, and polish them to a satin finish.

    3. John: Expect an update soon concerning project progress. I'm a little bit behind schedule because life gets in the way sometimes (preparing for finals, commencement, graduate school, etc.) but believe me, I want these kits to be shipped ASAP as much as you do!

  2. Hey Kevin, just had my fourth round of chemo, and my hands have started shaking, I was wondering if I break a wood part if I u could get/buy a replacement. Or If at all possible I buy a second kit?

    1. Certainly. Since I might not have an extra of every single part on hand, it may take 1 or 2 weeks to make, however. That said, though, none of the parts are particularly fragile :)

  3. I just filled out the mailing questionnaire, and there wasn't an option for the film adapter?

    1. Hi John,

      No need to worry about the roll film adapter if you added the $20 to your pledge.

  4. Hi,
    Kindly add us to your list of media contacts so that we may receive all releases emanating out of your organisation. Please feel free to discuss any specific story ideas that you may have.
    Best Regards,
    Chawm Ganguly
    46, Sarat Bose Road,
    Kolkata 700 020. India

  5. Hi Kevin,
    Is Duo still available?

  6. To use the voltmeter function to measure DC volts, turn the function switch to "V=" setting. Connect the black and red leads to the multimeter. The Multimeter Guide