Minolta MD-1 motor drive: Release problems fixed

[Andreas Thaler]

A Minolta MD-1 motor drive for the Minolta X series, which has misfires on the second release switch laterally and which I treated for the same reason last year.

In series operation on an X-500, it stops after a few shots and the red control LED on the back lights up.

I suspect contact problems based on the issues back then:

• I opened this MD-1 to check the installed electrolytic capacitors.
• After that there were problems with triggering.
• I attributed this to a cable that I had obviously crushed during assembly.
• I also replaced the release unit with the release button because fine wipers inside its circuit were bent and no longer had contact to their contact tracks.

After that the MD-1 worked faultlessly.

So I open the motor drive again to check the places I was working on back then.

I use a magnifying glass to examine the cable with the pinch but see no other damage.

The insulation seems intact, so there is no possibility of a short to ground, which I assumed was the cause of the problem when I first repaired it.

I use adhesive tape to fix the originally glued-on cable harness in its channel.

The soldering points on the contact strip for the connection to the camera also look good.

So everything should be ok here.

The contact springs on the second trigger open and close without any visible problems.

I spray electronics cleaner on the springs in case there are contact problems.

Overview

I close the case again.

The contact strip should only now be fixed with the two screws in order not to strain the connected cables inside by pulling.

I unscrew the trigger unit at the top of the handle.

I had replaced the unit, so I look at the soldering points.

They look okay, but they're not pretty because I obviously soldered them at too low a temperature.

So I resolder.

The red cable becomes too short after desoldering and removing a piece of the twisted cable strand. The trigger unit cannot be reassembled this way.

Therefore, I extend the cable with a short piece of a second one, which I solder on after tinning the cable ends.

A piece of blue shrink tubing insulates and additionally fixes the connection point.

To protect the other cables when the heat shrink tubing is heated, I slide a heatproof soldering mat underneath.

I heat the area with the Dremel Versatip, a butane gas burner.

Now I can put the trigger unit back on.

Before doing this I reworked some soldering points there.

An interim test is successful.

The upper leatherette is self-adhesive and can be easily reattached.

 

[Andreas Thaler]

The rubber shell on the handle is glued on.

I use a sharp scraper to remove the adhesive residue so that the shell sits smoothly again after sticking it on.

Reattach with Pliobond applied to both sides.

Leather coverings glued with this can be easily removed again.

Second test

Ohh, the motor drive stops again after a few triggering sequences in the single and series modes!

I measure the open circuit voltage of the batteries in the motor drive and the camera.

The one in the camera is already under nominal voltage.

I replace it with a fresh one and now the MD-1 works without any problems

It could also be possible that the X-500 with motor drive creates voltage problems in its circuits during continuous operation. Maybe the electrolytic capacitor that is no longer fit.

I'm not going to investigate any further and am content with the current status


Conclusion

• Errors that occur irregularly are more difficult to fix than those that occur regularly.
• In order to detect errors in components, a circuit diagram/service manual is required that provides information about electrical target values.
• Unfortunately I don't have a service manual for the MD-1.
• But even if so, these components must also be accessible.
• That would mean deeper dismantling here.
• Given the tight routing of the cables in the MD-1 this is a risky undertaking. And in my experience it is rare that it is actually an electronic component that no longer wants to work, with the exception of electrolytic capacitors.
• Troubleshooting here must therefore be limited to the “usual suspects”, i.e. contact problems, power supply, poor solder connections, as far as these spots can be reached without further dismantling.

And what was the cause of the problems and what repair measures helped?

I don't know it.

I think all of them together


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