Nikon DP-12 Service and Repair (Nikon F2AS)

[ic-racer]

I don't see much information on the Nikon DP-12 finder that comes with the Nikon F2AS, so I'll document my findings here.

My DP-12 initially seemed to work OK but likely the wiper just started pushing dirt around on the variable resistor (FRE), leading to erroneous indication of the LEDs.

In my case I had two issues.

1) The (-) light would come on and stay on when the shutter speed dial was past 1/125, no matter the lighting conditions.
2) The shutter speed numbers in the viewfinder were partially cut off in the viewfinder.
3) Deteriorating foam rubber.

First step was to remove the vinyl covering from the top and remove the top cover.

 

[ic-racer]

Likely the varialbe resistor element needs to be cleaned. This is called the "FRE." Occasionally these will go bad and will need to be replace. More likely, it just needs to be cleaned.

There is a piece of foam rubber covering the indicator LEDs. Remove that and replace it later with a new piece.

 

[ic-racer]

There is not any access to the FRE from inside the unit. So we will access it from the top. Remove the V-shaped LED light pipe.

 

[ic-racer]

It is a tight fit, but the end of a soft cleaning stick can reach the FRE. I used ethyl alcohol and DeOxit to clean it.

In my case cleaning the FRE solved the issue of the (-) light staying illuminated at shutter speeds greater than 1/125.

 

[ic-racer]

Fine tuning the light meter's response with a calibrated light source. The Nikon DP-12 service manual documents how to do the adjustment. Basically the front most trimmer outlined in yellow is the overall gain and the rear one adjusts the slope of the response. In my clase only a small tweak was needed.

I calibrated at EV5, 9 and 16. The manual asks for calibration at 0EV but who has a calibrated light source that dim?

BTW: don't adjust the trimmer at the very front (not circled).

 

[ic-racer]

Alignment of the shutter speed numbers in the viewfinder is the same as DP-2, DP-3 and DP-12. The adjustment is outlined in the service manual, but may not be entirely clear as to what to do.

There are two overlapping disks. One with teeth like a gear (#104) and the other with ridges and grooves (#107). They are not glued together and are touching only with friction.
The idea is to hold #107 stationary and tweak #104 one way or the other to align the numbers. A little trial and error is needed.

These are both very, very small. I used a 1mm screw driver and a needle tipped pickup. Unless the numers are way off, only a tiny nudge is needed.

 

[ic-racer]

I replaced two tiny strips of foam rubber here.

 

[ic-racer]

I replaced the foam here and on the other side.

 

[ic-racer]

All back together and working great!

Little know fact, when the AI lever is flipped up into the finder to use pre-AI lenses, a red filter moves over the f-stop indicator in the viewfinder, making the numbers red. Yes, normally one would not know this because pre-AI lenses don't have the little numbers. But, if you do flip the tab up, and mount an AI lens to use in Stop-Down meter mode, you will see the numbers are now red to indicate your AI lever is flipped up.

Another cool feature. When the viewfinder shutter is closed, the little red light on top becomes active and will illuminate when correct exposure is set. Otherwise, when the viewfinder shutter is open, the top light is a combinatyion battey check light and low-light shutter-speed illuminator. Too bad it does not also shine on the aperture ring.

 

[Andreas Thaler]

This is specialist work in mechanics and analog electronics, great!

 

[mshchem]

Specialist indeed! Well done!

 

[Bearman]

Competition for Solver Wong!? Nice work

 

[ic-racer]

Sover Wong, yes that is where I saw the illuminated F-stop scale modification!

 

[Chuck1]

Any idea if the prism in a dp1 is the same as the de1?

 

[ic-racer]

Any idea if the prism in a dp1 is the same as the de1?

Good question. Not sure, but I did see on Sover's site a DP-1 to kind of DE-1 conversion in metal. When I saw that I thought it might not be difficult to come up with a 3d printed cap for a failed DP-1 to make it more like the DE-1.

 

[qqphot]

I'm curious how you were able to remove the top cover. After removing the four visible screws under the vinyl, no part of the top cover showed any sign of loosening.

 

[Gregory_Nolan]

I'm curious how you were able to remove the top cover. After removing the four visible screws under the vinyl, no part of the top cover showed any sign of loosening.

Why four screws? There are only three screws under the leatherette at the top that need to be removed. If you look at the picture in post #1, you can see the three holes.

Also check out this screenshot from the official repair manual:

 

[qqphot]

There are four screws under the leatherette. Not knowing that only three of the four need to be removed, or which three, I removed all four. The top cover did not loosen or come free. So I asked here, to see if there were some further operation needed to free to top cover. It may be that my DP-12 is a variation from the one described here, it does look a bit different under the leatherette.

 

[Gregory_Nolan]

You also have to remove the front cover with the "Nikon" logo.

 

[qqphot]

You also have to remove the front cover with the "Nikon" logo.

I did that, but didn't touch anything under it. I wonder if one or more of those secure the top cover as well. But really, there was absolutely no give whatsoever after removing the screws under the top leatherette so I sort of wonder if something is glued in place, maybe by a previous inept repairer. (not like the current inept repairer!)