Nikon DP-20 Finder (for Nikon F4): Troubleshooting contact problems, disassembling, cleaning the interior and the optics

Andreas Thaler · Jan 29, 2025

There was a DP-20 finder for the Nikon F4 in my box of repair projects for a while now and I no longer knew what problems it had.

When I put it on my work F4 for a test, the upper display showed an impossible exposure compensation value and the lower LCD showed nothing at all.

Cleaning the contacts on the viewfinder and camera with electronics cleaner solved the problem.

Now I remembered that there is fungus on the optics. And my investigation showed that it was on the inside of the prism. At least that's what I thought.

So I had to take the viewfinder apart to get to the spot.

I didn't know whether I could reach the fungus or how the prism was constructed. The service manual didn't help either.

But I got an idea of how the viewfinder is constructed under the plastic cover, which provides additional protection for the inside of the housing.

There is a lot of dust to be seen here.

I already knew the DP-20 from two projects:

Nikon DP-20 viewfinder (for Nikon F4): LCD examined, case disassembled and reassembled

After replacing the top LCD in the viewfinder of a Nikon F4, I wanted to know what the procedure is for the bottom LCD. To do this, I dismantled a functional DP-20, the standard viewfinder for the F4, whose display is badly bleeding. It has black and green spots that partially cover the...

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Nikon DP-20 (for F4): Fall from 2.75 m height, LEDs shifted

The day had to come when I would cause my own repairs 😣 Today, while I was rearranging my cupboard, a DP-20 viewfinder for the F4 fell from a height of 2.75 metres onto the parquet floor. The viewfinder is intact on the outside, the glass inside is OK and the LCD works. However, the LED...

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This time I trusted my intuition and let my hand with the screwdriver run free.

Above the prism lies a flexible circuit board folded several times.

The prism is attached to the bottom of the housing with a screwed bracket.

Here it is.

Andreas Thaler · Jan 29, 2025

The prism is monolithic and cannot be disassembled.

I had to laugh because now I saw that the fungus was on the outside of the prism. So I didn't have to disassemble the DP-20 to clean it

But the eyepiece was dusty and so was the inside around it. So there was no harm in opening the DP-20.

I removed the fungus with hydrogen peroxide and cleaned with optic cleaner.

Cleaning the mirrors and lenses for the viewfinder displays with a blower, brush and optics cleaner.

The LCD sits on top of the prism.

The two silicon measuring cells, left and right of the eyepiece.

Here is now clean.

The dust on the lenses is gone. I just couldn't get to the front of the rear lens.

Andreas Thaler · Jan 29, 2025

This pin on the diopter correction drive …

… must be behind the front lens …

... then the lens can be moved back and forth using the rotary wheel on the right to adjust the focus in the viewfinder.

The DP-20 is now clean and works perfectly at the F4. It delivers exactly the same exposure values as its brother.

Andreas Thaler · Jan 29, 2025

Conclusion

The DP-20 is tightly installed but can be disassembled without any particular difficulties.
The flexible circuit board is fixed with three screws and can be lifted off to free the prism.
There is enough space for the cables, so there is little risk of them getting caught during assembly.

Nikon service manual for the DP-20 finder:

Arcticwolf`s Homepage

Nikon History, Nikon Service Manuals, Nikon Repair Manuals -free download-

ss-it.de

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

ic-racer · Jan 29, 2025

That cleaned up nice!

forest bagger · Jan 29, 2025

Great job, Andreas!
I had to clean those and other view finder sometimes, but never disassemble so entirely...

Andreas Thaler · Jan 30, 2025

Thank you very much, gentlemen!

LensReporter · Feb 2, 2025

Good morning Andreas

I have this problem with my DP-20, it doesn't recognize that the SB-22s is mounted on the F4 nor that the SB-700 is mounted in manual mode, I have cleaned several times all the hot shoe contacts, those on the body of the F5, and the gold plated contacts with DW-40 at first it gave regular results, from one moment to another the flash warning light appeared but it kept blinking as if the LED light didn't have enough voltage to stay on, it happens that it doesn't perform the automatic change to establish the correct shutter speed sometimes it does it well and it stayed on and starting this week literally it stopped recognizing the DP-20 that has a compatible flash mounted, it's not dirt on the contacts, it's not the SB22s or SB-700 flashes, it must be the sensor that recognizes that the compatible flash is mounted I'm not very interested in disassembling it since it could be either a transistor of those that are in the flexible printed circuit or this one, What do you suggest? Should I open it carefully to check the connections? Or should I buy another one in the future? Since the F4 is fine, the DP-20 is failing, well, it's more than thirty years old! For the rest, it works fine, although I feel that it doesn't nail the focus 100%, adjusting the frame again works fine for me.

Greetings!

Andreas Thaler · Feb 3, 2025

LensReporter said:
Good morning Andreas

I have this problem with my DP-20, it doesn't recognize that the SB-22s is mounted on the F4 nor that the SB-700 is mounted in manual mode, I have cleaned several times all the hot shoe contacts, those on the body of the F5, and the gold plated contacts with DW-40 at first it gave regular results, from one moment to another the flash warning light appeared but it kept blinking as if the LED light didn't have enough voltage to stay on, it happens that it doesn't perform the automatic change to establish the correct shutter speed sometimes it does it well and it stayed on and starting this week literally it stopped recognizing the DP-20 that has a compatible flash mounted, it's not dirt on the contacts, it's not the SB22s or SB-700 flashes, it must be the sensor that recognizes that the compatible flash is mounted I'm not very interested in disassembling it since it could be either a transistor of those that are in the flexible printed circuit or this one, What do you suggest? Should I open it carefully to check the connections? Or should I buy another one in the future? Since the F4 is fine, the DP-20 is failing, well, it's more than thirty years old! For the rest, it works fine, although I feel that it doesn't nail the focus 100%, adjusting the frame again works fine for me.

Greetings!

If we assume that it is rarely electronic components that break, but rather contact problems, I would look in this direction.

It could be solder joints that no longer conduct reliably, cables that have a bad connection, problems connecting circuit board parts, corrosion on contacts or even oxidation, which is often not visible.

I would look at all the contacts on the outside again with a magnifying glass and clean them with an eraser, then with electronic cleaner. More will not be possible from the outside without disassembling.

The same applies to the flash units.

I cannot say whether the SB-700 is compatible with the DP-20.

In any case, I would be very careful, also because of the high voltage in electronic flash units.

If electronic components in the devices are actually defective, I see little chances for a repair attempt.

Under no circumstances would I tinker with finder and flashes without further knowledge or endanger the electronics of the connected F4 (and myself).

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

Nikon DP-20 Finder (for Nikon F4): Troubleshooting contact problems, disassembling, cleaning the interior and the optics

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