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

[Andreas Thaler]

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 displayed digits.

After a quick look at the Nikon Service Manual for the DP-20 and reading a report on fungus removal in this viewfinder, I got to work.

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The candidate in beautiful external condition.

Loosen the screws on the bottom and side (2 x 4 screws).

I have already removed the two cover caps on the rotary switches for the diopter corrector and the exposure metering mode. The screws underneath must be loosened so that the top cover can be removed.

The cover caps, as well as the two rotary switches, are made of soft plastic.

The caps are glued in. They can only be levered out, leaving unavoidable marks.

I used a flathead screwdriver with a small blade for this.

The screws are loosened.

Under the cover

The front of the viewfinder.

On the left is the rotary wheel for adapting the exposure metering system to different focusing screens. The wheel is operated via an adjusting screw on the underside of the viewfinder.

The LCD is located on the front of the viewfinder.

Above it is the illuminator with two turquoise LEDs on the left and right, which consists of a prism.

In order to access the LCD, a bracket, which is held in place by two screws, must be removed.

The bracket and its two screws.

The prism hangs on two cables and can be lifted.

Below is the LCD, which sits with its two conductive rubbers on contacts on the flexible circuit board.

The LCD can be carefully removed from the contacts using the angled probe.

 

[Andreas Thaler]

The removed display.

The light gray spots turn black as soon as voltage is applied to the LCD.

On the two long sides are the conductive rubbers that electrically connect the LCD to the contacts underneath on the circuit board.

Since I don't have an LCD to replace, I'll reinstall the existing LCD.

The four bottom screws that hold the cover under the top cover are back in place.

Here you can see the drive for the diopter correction of the eyepiece, which is operated from the outside using a rotary switch.

As you rotate, part of the eyepiece inside the viewfinder moves back and forth

The red slats of the eyepiece shutter, which is activated via a lever on the outside.

The case is reassembled.

The two cover caps for the rotary switches are fixed with Pliobond.

The damage caused by prying it out beforehand was limited; I was able to smooth out the areas with the blade of the screwdriver.

Testing the reassembled viewfinder on the F4.

Both displays work.

The upper display is integrated into the camera housing and is reflected.

The lower LCD that I examined earlier and is part of the viewfinder shows severe bleeding. But you can still work with it.

The test run to replace the lower LCD was successful

This DP-20, which arrived from Germany today, remains unopened.

Its LCD is almost perfect, the abrasion on the case gives it dignity

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Nikon F4: Upper LCD replaced

Today I opened some packages of cameras that I received last year. There was also a Nikon F4S that I hadn't even thought about. Clearly used extensively, signs of use, but with a flawless viewfinder LCD at the top and a LCD at the bottom with only a small dark spot. Unfortunately, the fact...

www.photrio.com

Nikon DP-20 finder for the F4

Recently, as part of a beautiful, practically unused, late model Nikon F4s which (ahem) came my way, I immediately noticed a problem with the DP-20 finder. There was quite a heavy infestation of fu…

jrhughes.wordpress.com

The complex structure of the DP-20 viewfinder.

(Page 47, PDF)

http://ss-it.de/data/finder/F4%20Finder%20DP-20.pdf

 

[Andreas Thaler]

(Page 15, PDF)

http://ss-it.de/data/finder/F4 Finder DP-20.pdf


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

 

[LensReporter]

Hello good friend

Excellent thread, a few years ago I saw that piece on e-bay, I should have bought it, now I have to buy a viewfinder that is very damaged on the outside to hopefully get an LCD in very good condition.

 

[Andreas Thaler]

Excellent thread, a few years ago I saw that piece on e-bay, I should have bought it, now I have to buy a viewfinder that is very damaged on the outside to hopefully get an LCD in very good condition.

Thank you!

There should be some DP-20 finders available, certainly from Japanese dealers on eBay.

 

[LensReporter]

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 F4, 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!

 

[LensReporter]

Hello Andreas, I hope you are well my friend, I tell you that I bought on eBay a body that has the lower LCD in good condition, the upper LCD is useless but finally I have a precious body to practice disassembling and assembling the body, I also bought a set of JIS screwdrivers, what I could not buy is the Knipex 46 21 A01 pliers to remove the retaining ring of the rewind lever, but that one is expensive and Amazon does not offer the import service to Mexico, only to Spain and from there to Mexico, little by little I will buy what I need, the soldering iron will surely also buy it later along with the Flux, I already have a 3mm roll of solder, looking at the shots it seems that the shutter is not damaged we will see when I receive it, on the other hand my F4 did not present the fault that I had with the flash apparently it was the IR filter that did not respond yesterday I tried it and at first it recognized the SB-22s and made the shutter speed synchronization changes, you already know I'll comment on my progress later, goodbye friend.

 

[LensReporter]

 

[LensReporter]

 

[LensReporter]

Yesterday Saturday I got the courage to take the shutter apart, of course the one that was changed! That's when I realized that the screwdrivers I had were useless because they only had #0 and they should be narrower and finer cross JIS #00, #000 and #0000, it took me a while but I had a lot of fun apart from analyzing how complicated its design was so advanced for 1988, it has two golden washers and a plastic retainer plus the frames and the sides apart from the metal arm that holds the frame, the carbon fiber curtains with epoxy coating and the aluminum ones are different in tone but over time they darken, that shutter had a fault in the transistors that control the power flow to the electromagnets, apart from changing both sets of curtains the transistors would have to be changed and the shutter calibrated, mission impossible.

 

[Andreas Thaler]

Thanks for the update!

Good luck with your work. Would you like to keep us updated with reports?

Knipex is just one good manufacturer, but there are many others, of course.

Regarding the JIS screwdrivers, I would also recommend the longer versions with a larger handle, which gives you more torque. You'll definitely need them for the screws for the tripod mount on the F4, which are glued.

Vessel is indeed the only recommendation I can think of:

3-Piece Micro Screwdriver Set No.9902E(9900 3 pc. set) | PRODUCTS INFORMATION | VESSEL CO., INC

full range of information on product groups ranging from tightening tools such as drivers, bit sockets and air tools to anti-static products in the factory

www.vessel.co.jp

 

[Andreas Thaler]

that shutter had a fault in the transistors that control the power flow to the electromagnets, apart from changing both sets of curtains the transistors would have to be changed and the shutter calibrated, mission impossible.

You can desolder the transistors on the shutter board with hot air; they're SMD components. But you should practice this beforehand.

Soldering them across the three connections is easy with a soldering iron.

To test the functionality of such transistors, I desolder them and plug them into my component tester. But you can also do it with a multimeter; there are instructions online.

If the transistors are defective, e.g., due to overload, there's a reason I should find out so that the next transistors don't fail again.