This post follows up:
When I checked the motor drive, I saw that the attached Nikon F3P fired continuously not only in C(ontinous) but also in S(ingle) mode.
That wouldn't be a problem, I can take my finger off the trigger if I want to take single pictures.
But I wanted to fix this.
I suspected a switch in the handle of the MD-4, which sits on a small circuit board and has two double contact tabs.
I hope that „tab“ is the right word in English, an alternative would be „tounge“? Please see the next but one picture below.
If you turn the operating mode selector on top of the handle, a contact is interrupted in C mode, the camera works in continuous operation as long as the shutter button is pressed.
Operating mode selector on top of the handle of the MD-4 with shutter button in the center.
If it does this even in S mode, there must be a mechanical problem with the switch.
And sure enough, one of the pairs of contact tabs didn't close as it was bent.
Bending metal contact tabs back so that they close again is difficult, it didn't work here either.
I looked at the matter
on a switch block removed from an abandoned MD-4 which I already had dissected, see
Here is the switch with the contact tabs, which are ok.
It's about the right couple.
The arrow points to the outer tab, which is curved outwards in the broken MD-4.
Here I have already partially removed the flexible circuit board:
In order to bring the tab to pressure, as seen here, I would have to bend it behind its counterpart.
This doesn't work as long as it's installed.
The pair of tabs on the left, which forms an open switch, shows the situation as I currently have it in the broken motor drive.
Maybe it would work if I can make a bend about 5 mm in front of where the bent tab is attached to the block. But I'm skeptical about that.
A craft solution
So I tied the tabs together with a fine jumper wire. And to reinforce it, the tip of a toothpick was used as a wedge:
The opposite station of the small „cable car“ is one of the power transistors in the handle of the MD-4.
I threaded the wire through the hole for attaching a cooling plate and fixed the work with a drop of Loctite:
It worked!
However, this means that there is constant tension on the transistor, which could affect the soldering point in the long term.
So I thought about what else I could do.
Repaired with original spare part
The next day I tackled the matter directly, I had already thought about it enough beforehand.
I had mentally bent the tab, glued it, soldered it or left it as I had fixed it using the „cable car“.
But everything wasn't convincing to me.
I wanted it the way it was before the damage.
The rest of the story is quickly told:
I removed the undamaged contact tab from the abandoned MD-4, removed the damaged one, and installed the replacement.
This was surprisingly easy.
Loosened a screw, removed the washers, removed the soldering point on the flexible conductor track with the desoldering pump, did everything again in reverse order and set the soldering point.
Everything is as if nothing had ever been broken
The arrow points to the „new“ contact tab:
I used the multimeter to check the closed switch for continuity.
„Beep!“ - the switch closes as it should:
The green power transistor on which I mounted the „cable car“ is almost back to its original optical condition. Cable, toothpick tip to tighten the pull and glue are removed.
The scratched finish doesn't matter, the main thing is that the transistor switches as expected:
The board with the switch block (the arrow points to the front pair of contact tabs, the repaired one is behind it and cannot be seen here) was also installed back into the handle of the motor drive without damaging the renewed contact tab:
I ran a test film with the motor drive, tested single frame (S) and continuous frame (C) on the MD-4 and rewound the film using the motor.
Everything works and the film is not completely drawn into the cartridge via the stop back MF-6 as it should:
As you can see, it's worth having spare parts and not throwing anything away
+++
All information provided without guarantee and use at your own risk.
Nikon MD-4 Motor Drive: Issues with rotary switch and rewind resolved, cleaning
The MD-4 on my table has been through a lot. It accompanied the F3 Press on which I replaced the exposure compensation wheel. What's even more pleasing is that it works on the F3 Press and only has minor problems: The rotary switch around the trigger for setting the motor operating mode (L...
When I checked the motor drive, I saw that the attached Nikon F3P fired continuously not only in C(ontinous) but also in S(ingle) mode.
That wouldn't be a problem, I can take my finger off the trigger if I want to take single pictures.
But I wanted to fix this.
I suspected a switch in the handle of the MD-4, which sits on a small circuit board and has two double contact tabs.
I hope that „tab“ is the right word in English, an alternative would be „tounge“? Please see the next but one picture below.
If you turn the operating mode selector on top of the handle, a contact is interrupted in C mode, the camera works in continuous operation as long as the shutter button is pressed.
Operating mode selector on top of the handle of the MD-4 with shutter button in the center.
If it does this even in S mode, there must be a mechanical problem with the switch.
And sure enough, one of the pairs of contact tabs didn't close as it was bent.
Bending metal contact tabs back so that they close again is difficult, it didn't work here either.
I looked at the matter
on a switch block removed from an abandoned MD-4 which I already had dissected, see
Nikon MD-4 Motor Drive: A dissection
I wanted to know exactly and dismantled my practice MD-4. Actually, at first I was only interested in how I could remove the battery contact plate in the battery compartment. Another MD-4 has traces of corrosion at this point that I cannot satisfactorily remove from the outside. And then I...
Here is the switch with the contact tabs, which are ok.
It's about the right couple.
The arrow points to the outer tab, which is curved outwards in the broken MD-4.
Here I have already partially removed the flexible circuit board:
In order to bring the tab to pressure, as seen here, I would have to bend it behind its counterpart.
This doesn't work as long as it's installed.
The pair of tabs on the left, which forms an open switch, shows the situation as I currently have it in the broken motor drive.
Maybe it would work if I can make a bend about 5 mm in front of where the bent tab is attached to the block. But I'm skeptical about that.
A craft solution
So I tied the tabs together with a fine jumper wire. And to reinforce it, the tip of a toothpick was used as a wedge:
The opposite station of the small „cable car“ is one of the power transistors in the handle of the MD-4.
I threaded the wire through the hole for attaching a cooling plate and fixed the work with a drop of Loctite:
It worked!
However, this means that there is constant tension on the transistor, which could affect the soldering point in the long term.
So I thought about what else I could do.
Repaired with original spare part
The next day I tackled the matter directly, I had already thought about it enough beforehand.
I had mentally bent the tab, glued it, soldered it or left it as I had fixed it using the „cable car“.
But everything wasn't convincing to me.
I wanted it the way it was before the damage.
The rest of the story is quickly told:
I removed the undamaged contact tab from the abandoned MD-4, removed the damaged one, and installed the replacement.
This was surprisingly easy.
Loosened a screw, removed the washers, removed the soldering point on the flexible conductor track with the desoldering pump, did everything again in reverse order and set the soldering point.
Everything is as if nothing had ever been broken
The arrow points to the „new“ contact tab:
I used the multimeter to check the closed switch for continuity.
„Beep!“ - the switch closes as it should:
The green power transistor on which I mounted the „cable car“ is almost back to its original optical condition. Cable, toothpick tip to tighten the pull and glue are removed.
The scratched finish doesn't matter, the main thing is that the transistor switches as expected:
The board with the switch block (the arrow points to the front pair of contact tabs, the repaired one is behind it and cannot be seen here) was also installed back into the handle of the motor drive without damaging the renewed contact tab:
I ran a test film with the motor drive, tested single frame (S) and continuous frame (C) on the MD-4 and rewound the film using the motor.
Everything works and the film is not completely drawn into the cartridge via the stop back MF-6 as it should:
As you can see, it's worth having spare parts and not throwing anything away
+++
All information provided without guarantee and use at your own risk.
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