Nikon MD-12 Motor Drive renovated

A friend had asked me to look at his Nikon MD-12 Motor Drive.

The Motor Drive for the Nikon FE(2) and FM(2) hasn't been available for a long time. A contact in the battery compartment was corroded but was poorly cleaned.

I didn't say yes right away because I usually only work on my own stuff. But it motivated me to treat a “foreign device” for once. Because it shouldn't be returned to its owner any more broken than before.

A challenge


A long day begins

To access the screws that hold the MD-12 together, the leatherette must be removed.

Simply lift carefully at one end with the probe and then slowly pull it off.







It took me some time before I could remove the battery compartment under the motor control gear. Something wouldn't let go.

The two cables that lead from the battery contacts to the motor are tight. They resist:





In order to be able to fold out the battery compartment, I unsoldered both cables.

Other cables allowed more freedom of movement. I also unsoldered these because I wanted to leave the battery compartment free for a thorough cleaning.

And that was required:





Another example of how batteries can take revenge over the years if you forget them in the device

The motor control gear looked better.

Some dirt on the outside and on the gears which I removed. But otherwise the MD-12 is still good at lubrication:





The battery compartment dismantled:





Close-up of horror:





All parts were soaked in Durgol Universal descaler solution diluted with water for 40 minutes.

My best tip against battery acid residues:





A look at the clean board:





The ON/OFF switch was stiff.

A dose of electronics cleaner, sprayed directly onto the built-in contacts of the slide switch, changed that:





Meanwhile, bathing time in Durgol was over.

Rinse with water, dry:





Drying is quicker with a hot air blower:





And now the hard part of the work began.

In order to be able to reassemble the motor, all cables must first be soldered back on.

Since the wiring is very tight, I extended the cables and replaced the soldering points.

It took several tries before I was happy with the result.

• Insulation scorched by the soldering tip,
• disconnected cables,
• short circuit in the battery compartment due to solder bridge causing hot batteries,
• ugly solder points that would haunt me into my dreams if I didn't redo them

and other adversities had to be encountered.

In between, assembly with tests on my Nikon FM2n.

Very useful tutorial for me… thanks!

I bought a MD-12 that “machine guns”. Despite reading the repair manual and isolating the one or two potential causes, I remain intimidated by the disassembly procedure. But now that I see it…

Slowly the MD-12 came to life


I was also able to solve the problem that the motor started rattling after I switched it on without me having pressed the shutter button.

And I solved the problem in a brutal way.

The switch behind the plug contact on the motor handle was responsible for the incorrect switching.

I couldn't figure out how or why. Not even how the switch switched.

So I cut its wiring.

When I then put the ground cable to the plug contact back in place, the MD-12 was back in sync.

Doing this I sacrificed some of the functionality of the motor drive.

But it worked again.

Since the owner doesn't want to use the motor drive for photography, but instead wants to look at it in the display case, I was able to take responsibility for that.

Of course that's not ideal


The Dremel Stylo removed stubborn corrosion residues:







The plate with the four battery contacts in the battery compartment.

I couldn't remove the acid residue under the plate because it is riveted:





A special kind of "soldering bridge"

However, there was no other way I could get a certain cable into position for soldering:





The new order in the cable world of the MD-12:





I sealed the ends of the cut cables with Loctite to prevent them from conducting.





After assembly, the motor occasionally stalled during continuous operation.

After I cleaned all contacts on the motor and camera with electronics cleaner, this problem was also solved.


And there he is again, the MD-12, with his new friend FM2n, also cleaned on the outside and ready for work:







As always, the table had become too small after a day's work:





Conclusion

• Not an easy job, but I kept at it until it worked.
• In any case, I will remind my friend to only use the motor under supervision and then remove the batteries.
• Another short circuit cannot be ruled out, even though I checked everything meticulously before assembling it. Because there is very little space for the cables in the housing when the motor is reinserted. During one of the first attempts I frayed the positive cable and there was a short to ground. The battery compartment quickly became hot.
• Nikon's fitters had their system for proper assembling, which of course I don't know. Beside this the cable harness to the battery compartment was attached with adhesive strips that had rotted away.
• The difficulty lay in assembling the cables in a way that was gentle on the cables.

Anyway in all a good day

+++

All information provided without guarantee and use at your own risk.

BrianShaw said:

Very useful tutorial for me… thanks!

I bought a MD-12 that “machine guns”. Despite reading the repair manual and isolating the one or two potential causes, I remain intimidated by the disassembly procedure. But now that I see it…

Click to expand...

Good luck!

Nice job!

It is good to see metal gears inside!

ic-racer said:

Nice job!

It is good to see metal gears inside!

Click to expand...

Thanks, and you are right

The Nikon MD-2 e. g. has one or more gears made of plastic, see on the site of Sover Wong:

A breaking point.

I posted a little information about disassembling the MD-11 / MD-12 here: https://www.photrio.com/forum/threa...-a-film-camera-these-days.195158/post-2709631 but only one photo.

IIRC, one has to find and remove all screws (I think there are 9) around the upper side under the leatherette to separate the top part from the bottom. The power wires and the wires to the port for the remote/MR-3 aux shutter button on the bottom front will still be connecting the top and bottom, so don't pull too hard or they can break.

Andreas's first picture shows 3 screws in a row vertically, of which I think you need to remove only the top screw (1 of the 9) to separate the halves. The lower two screws are holding the internal plate that has the battery contacts.

Apart from corroded contacts, many dead MD-11/12 may simply be broken/frayed wires from the battery contacts to the PC board. That's what was wrong with mine.

I'm not sure about the cause of the rattling or machine-gunning described by Andreas and BrianShaw, but it might be a short inside the wiring that goes to the remote/MR-3 port, or shorted/bent pins in the port. Those wires should be open-circuit unless you actually have something connected to the port, I think.

reddesert said:

I posted a little information about disassembling the MD-11 / MD-12 here: https://www.photrio.com/forum/threa...-a-film-camera-these-days.195158/post-2709631 but only one photo.

IIRC, one has to find and remove all screws (I think there are 9) around the upper side under the leatherette to separate the top part from the bottom. The power wires and the wires to the port for the remote/MR-3 aux shutter button on the bottom front will still be connecting the top and bottom, so don't pull too hard or they can break.

Andreas's first picture shows 3 screws in a row vertically, of which I think you need to remove only the top screw (1 of the 9) to separate the halves. The lower two screws are holding the internal plate that has the battery contacts.

Apart from corroded contacts, many dead MD-11/12 may simply be broken/frayed wires from the battery contacts to the PC board. That's what was wrong with mine.

I'm not sure about the cause of the rattling or machine-gunning described by Andreas and BrianShaw, but it might be a short inside the wiring that goes to the remote/MR-3 port, or shorted/bent pins in the port. Those wires should be open-circuit unless you actually have something connected to the port, I think.

Click to expand...

In your post there's photo of the DC motor. It's not really clear other than Matsushita 12VDC. Have you had chance to record what is the exact type of the motor?
I have the repair manual for MD-12 and it doesn't have any details for the motor. I have one extra MD-12 and been thinking to mod it with higher RPM motor. Who knows from 3.5 fps maybe I can get 5 fps.