Nikon MK-1 Firing rate converter: A look inside and cleaning the switch contacts

[Andreas Thaler]

Two flagships and rivals of the 1980s:

Canon New F-1 with Motor Drive FN and Nikon F3 with MD-4 and MK-1, which is mounted below the motor drive.


The Nikon F3 and its exclusive motor drive MD-4 are a perfectly matched pair.

The MD-4 not only cocks the shutter and transports the film, but also makes the F3 more comfortable to hold.

In continuous (C) mode, the MD-4 speeds up the film to 5.5 fps (frames per second), powered by eight AA batteries.


Nikon MK-1: Speed control and shutter release in portrait format

However, you don't always need that much speed, so the Nikon MK-1 firing rate converter is the third in the group.

It reduces the film transport speed to either 1, 2 or 3 fps or leaves it at 5.5 fps. It also offers a second shutter release with which the F3 can be conveniently fired in portrait format.

The MK-1, which is fixed to the underside of the MD-4 using two screws, does not require additional batteries.


A look inside and repair of the trigger

Now available in sufficient numbers on the used market, the MK-1 is an accessory that is made of metal just as solidly as the F3 and MD-4.

Nikon MK-1, control wheel with shutter release in the middle:

Set the motor speed to 1 frames per second (C1), 2 fps (C2), 3 fps (C3) or film transport at full speed of 5.5 fps (C/S).

OFF locks the shutter release, the film transport speed remains at 5.5 fps provided by the MD-4.


I own a few of these, some of them heavily used, which do their job perfectly.

However, the shutter release on one of them no longer works reliably.

A good opportunity to take a look inside the MK-1 and familiarize yourself with the Nikon Repair Manual for the MK-1.

I was able to acquire the only one (original, no reprint) that was offered on eBay and it is currently on its way to Vienna

As soon as it arrives, it starts.

Stay tuned

---

Nikon MK-1 firing rate converter at mir.com.my:

Nikon MD-4 Motor Drive - Part V

Nikon MK-1 firing rate converter instruction manual, PDF user manual

Nikon MK-1 firing rate converter instruction manual

www.butkus.org

 

[forest bagger]

Aren't the 5.5 fps with 8 AA batteries, and with the Nikon battery pack (14 NiCd-cells) it will be 8 fps?

 

[Andreas Thaler]

Aren't the 5.5 fps with 8 AA batteries, and with the Nikon battery pack (12 NiCd-cells) it will be 8 fps?

Yes, that is possible.

It's just that my MN-2 battery unit is no longer capable of doing that

Nikon MN-2 Battery Unit: Dirty job

An MD-4 motor drive with Ni-Cd battery pack MN-2 came to me. As defective - the way I like it, because there is something to see and to do 👍 The battery pack provides 16.8 volts for the motor. Pretty strong. Coincidentally, the associated service manual is available 😉 Here the battery...

www.photrio.com

 

[Mick Fagan]

With the mirror locked up, the F3 does approximately 6 fps. I know this as one of my F3 bodies was used with a 250 frame back (10m of film) and we used a stopwatch to work out actual frame rate.

We were doing a photo shoot for a television advertisement, in the days when money grew on trees in the advertising industry; 1980's. We borrowed (hired?) the 250 frame back from a local school and event photography company, which had about 6 or so 250 frame backs.

We also borrowed/hired from someone else, the Nikon MA-4 converter. Basically we spent two days doing some inane walk in, walk out of various models dressed in silly costumes. The end result was approximately 3 seconds of air time in a 30 second commercial.

One thing I did learn, was that the fastest the camera ran, was about 5.9 fps with the mirror locked up, and taking 10m of film out of the bulk back then loading them into a Colenta roller transport processor, didn't add any scratches to the film. The film was then contacted printed onto B&W Kodak print film for a B&W movie projector to display the image on a projector screen when the final advertisement was shot using colour film.

This link shows a multi picture arrangement of the MA-4, hover your mouse over the bottom right image to highlight the F3. This is pretty much how my F3 body was set up, awesome piece of kit, but I remember it took a little while to understand exactly how things worked and at 5.9 fps we went through 10m of film in around 40 seconds; give or take. Another way to look at it is that a roll of 36 frames, takes around 6 seconds.

Nikon MA-4 AC/DC Converter 1470

This web site documents my Nikon F collection and is trying to show the evolution of the Nikon F System. The site is not finished (will never be) and I am continously adding subjects.

www.destoutz.ch

 

[AnselMortensen]

I only knew these existed because of the Del's Camera ads in Shutterbug back in the day...but I forgot all about them.
Now I want one.
My G.A.S. thanks you....(I think)

 

[mshchem]

The converter is more expensive than the motor drive. It's a cool thing.

 

[Andreas Thaler]

I only knew these existed because of the Del's Camera ads in Shutterbug back in the day...but I forgot all about them.
Now I want one.
My G.A.S. thanks you....(I think)

It's a pleasure!

 

[forest bagger]

It's just that my MN-2 battery unit is no longer capable of doing that

I know someone who is replacing a worn out battery unit (14 NiCd cells in 2/3 AA size) with 14 new NiCd cells in 1/2 AA size which he puts in the normal battery holder for 8 normal cells in 1/1 AA size.

 

[Andreas Thaler]

I know someone who is replacing a worn out battery unit (14 NiCd cells in 2/3 AA size) with 14 new NiCd cells in 1/2 AA size which he puts in the normal battery holder for 8 normal cells in 1/1 AA size.

That can only be you!

 

[forest bagger]

Definitively not!
That man usually uses modern Nikon DSLRs (e.g. D850) and lenses.
Some weeks ago he additionally wanted to buy an old Nikon F3 HP with MD-4 to work with film, now he got both.
He wants to use it with maximum fps but doesn't want to spend money for an old Nikon battery unit, assuming its NiCd cells would be as rotten as in yours, Andreas.
And now he found a source for new NiCd cells.

I can imagine that you'd be happy if he tells me this source so that I can tell it to you, Andreas.

 

[Andreas Thaler]

Definitively not!
That man usually uses modern Nikon DSLRs (e.g. D850) and lenses.
Some weeks ago he additionally wanted to buy an old Nikon F3 HP with MD-4 to work with film, now he got both.
He wants to use it with maximum fps but doesn't want to spend money for an old Nikon battery unit, assuming its NiCd cells would be as rotten as in yours, Andreas.
And now he found a source for new NiCd cells.

I can imagine that you'd be happy if he tells me this source so that I can tell it to you, Andreas.

Thanks, that's very interesting, but I don't have a charger and the battery holder is broken, so I'll stick with AA batteries.

 

[Chan Tran]

View attachment 375816

Yes, that is possible.

It's just that my MN-2 battery unit is no longer capable of doing that

Nikon MN-2 Battery Unit: Dirty job

An MD-4 motor drive with Ni-Cd battery pack MN-2 came to me. As defective - the way I like it, because there is something to see and to do 👍 The battery pack provides 16.8 volts for the motor. Pretty strong. Coincidentally, the associated service manual is available 😉 Here the battery...

www.photrio.com

The MN-2 pack has 14 NiCad cells and capable of 5.5fps. With 8AA the MD-4 is only 3.8fps. I recelled the MN-2 with NiMH which last 3 times as long as the origninal. The MN-2 is quite easy to take apart as it has screws. You don't have to break it apart. The original cells are rated at 270mAh. I bought 800mAh cells.

 

[mshchem]

The MN-2 pack has 14 NiCad cells and capable of 5.5fps. With 8AA the MD-4 is only 3.8fps. I recelled the MN-2 with NiMH which last 3 times as long as the origninal. The MN-2 is quite easy to take apart as it has screws. You don't have to break it apart. The original cells are rated at 270mAh. I bought 800mAh cells.

Expand on this topic. I have mn-? for Nikon F5 I would like to rebuild. I don't know why

 

[Chan Tran]

Expand on this topic. I have mn-? for Nikon F5 I would like to rebuild. I don't know why

The MN-30 for the F5 is harder to rebuild because you have to cut it open then reglue it. The incentive? It's the only way to get the 8fps on the F5. Even when I use the external power (which I can crank up the voltage) I can't get more than 7.4fps.

 

[mshchem]

The MN-30 for the F5 is harder to rebuild because you have to cut it open then reglue it. The incentive? It's the only way to get the 8fps on the F5. Even when I use the external power (which I can crank up the voltage) I can't get more than 7.4fps.

Yes, I have a couple that have been cut open once. It's a complete waste of time, maybe someday

 

[Andreas Thaler]

It's impressive what you do with the battery packs.

Has anyone ever opened a Nikon F5 or even repaired it?

 

[Chan Tran]

Yes, I have a couple that have been cut open once. It's a complete waste of time, maybe someday

I wish I have one so I can cut it open and see if I can recell it.

 

[Andreas Thaler]

The repair manual has just arrived, so we're getting started.

Since I can't remember which of my MK-1s had the problem with the switch, I'm taking the one with the most signs of wear.

I generally stay away from devices that work. But here it makes sense to make an exception, since the switch contacts will probably need to be cleaned.

 

[Andreas Thaler]

Disassembly

The MK-1 is fixed to the bottom of the Motor Drive MD-4 with two screw connections, which according to the user manual should be loosened or tightened in a specific order, see:

Nikon MK-1 firing rate converter instruction manual, PDF user manual

Nikon MK-1 firing rate converter instruction manual

www.butkus.org

Loosening the screws.

Removing the upper cover plate.

To remove the assembly with the switch, these three screws are loosened.

The switch contacts with wipers and contact tracks.

The wipers rotate with the rotary switch that clicks into place in steps.

The trigger moves its two contacts forward and contacts a two-stage switch.

I will clean the contact tracks, wipers and switches.

 

[Andreas Thaler]

Next we move on to the circuit board.

Analog electronics with discrete components (resistors, transistors, tantalum capacitors, diode, trim potentiometer) and an IC.

I can't find a data sheet for the IC online.

According to the circuit diagram in the repair manual, it is an operational amplifier.

Overview

The connection to the MD-4 and cover.

Dirt has accumulated here, which I will also remove.

Excerpt from the circuit diagram.

It is actually an operational amplifier (triangle) which could be connected here as a comparator.

Two voltages at the two inputs (+/-) are compared, and the larger of the two voltages is amplified at the output and is either positive or negative.

 

[Andreas Thaler]

Cleaning and reassembly

Bellows, electronic cleaner, cleaning swabs.

Dirt has accumulated in the recesses, which I remove with isopropyl alcohol.

First, the plastic cover is mounted with the four screws, then the ring is put on and secured with its screw.

It doesn't work in the reverse order because the ring partially covers the drill holes for the screws.

I check all the soldering points.

No complaints here.

Mounting the retaining plate for the rotary switch with three screws.

The cover plate is placed on.

Only then is the assembly with the rotary switch screwed on as it covers the vertical part of the cover plate.

Ready

Test on the F3 with MD-4 - everything is fine

 

[Andreas Thaler]

Conclusion

• The MK-1 is solidly made of metal with some plastic parts.
• The analog electronics are straightforward and I assume troubleshooting based on the circuit diagram is feasible.
• All electronic components should be industry standard and still be available new on the market today.
• The operational amplifier should be replaceable with one of the available models.
• The MK-1 is designed simply and easy to service.

+++

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

 

[forest bagger]

Good work, Andreas!

 

[Andreas Thaler]

Good work, Andreas!

Thanks, Michael!

 

[forest bagger]

Thanks, Michael!

By the way - can you say something about that?

Nikon 105/2.5 AI-S front ring engraving white or yellow?

Hi guys, I have a Nikon 105/2.5 AI-S lens here that has a very high serial number. In contrast to all the examples I know, the engraving on the front ring is not pure white but lemon yellow. Is this intentional given the high serial number, or is the white yellowed? Cleaning does not help!

www.photrio.com