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Nikon F4: Upper LCD replaced

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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 that the LCDs can get black and colorful spots over the decades - the so called „LCD bleeding“ - is a weak point of the F4.

The two automatic programs and shutter priority do not work. The camera exposes everything with the smallest aperture that must be preset for automatic shooting. So an irreparable damage, at least for me.

Since I have a second F4 that works, but both LCDs are badly bleeding, I decided to replace the LCDs.


The bottom LCD

was easy to replace as I only had to exchange the DP-20 viewfinder which is intended to be exchanged with other viewfinders. The LCD is integrated in the viewfinder and shows, among other things, exposure time, aperture, exposure metering mode and adjustment for manual exposure setting.


The upper LCD

however, which displays the image counter and the exposure compensation values in +/- 1/3 increments, is integrated into the camera.

To exchange the upper LCD I only had one attempt. If I had damaged the replacement LCD or the corresponding electronics in the acceptor F4, the function of the latter would have been limited at least.

I reconsidered everything and took the risk.

And it worked 🙃



1.jpg


2.jpg


To access the upper LCD (on the left), these screws are loosened.


3.jpg


The unit with the LCD, its electronic illumination, the prism for light entry and the LEDs for focus and exposure correction (on the left) hangs on a flexible circuit board after the screws have been loosened. The bottom cover is already detached.


4.jpg


The LCD lies with its conductive rubbers on the contacts on the flexible circuit board. Above this is the prism, which is fixed by a bracket with two screws. The bracket, prism and LCD are already removed here.

The electronic illuminator lies on the prism and hangs on two cables. It can be seen here, the bright flat cuboid.

The structure corresponds to that of the Nikon F3(/T):



5.jpg


Bracket with screws, prism and LCD


6.jpg


All disassembled parts at a glance.

These are the components from the donor F4. Only the LCD (defective) is from the acceptor F4.

Since the camera has already become a spare parts donor, I disconnected the unit with the replacement LCD in order to be able to work on it better. For this I cut the flexible circuit board.


7.jpg


The broken display. If there is voltage, the light gray spots turn black. This means that the digits can no longer be read at this point.


8.jpg


The replacement LCD at its new workplace.


9.jpg


On the left the spare F4S and on the right the F4 with two - almost - new LCD.


+++

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


From the service manual for the Nikon F4 (page 9 in the PDF). Only the marked parts need to be removed or detached.

The LCD is connected to the contacts on the board via two conductive rubbers and just rests there.

On my F4, the conductive rubbers stuck to the contacts a bit, so I carefully lifted out the LCD with an angled probe.

Be careful not to detach the conductive rubbers from the LCD and ensure that the LCD is then installed sideways accurate to side. In my example I saw impressions of the contact rows in the conductive rubbers, which helped with orientation.

The flexible printed circuit board, on which the entire unit hangs on the housing after loosening the three fastening screws, is robust but must not be bent or pinched. It can be pulled out carefully a little and then pushed back into the housing.

It's best to study the setup on your donor camera and take photos/notes as always.

The electronic illuminator is interesting. I think it's an LED behind a turquoise green cover. The light source is point-shaped. Maybe @koraks knows more about this.


 
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1.jpg


The larger LCD in the DP-20 viewfinder has its own illumination, which is also turquoise green. This is also likely to be an LED, as the anode and cathode are labeled.

It would be interesting to see the inside of the DP-20.

A complex construction made of optics, electronics, metal and plastic.

Maybe I'll dissect the DP-20 with the severe LCD bleeding. However, it still works and it would be a shame to dismantle it.



(Page 15, PDF)
 
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By the way, the DP-20 replacement has three small fungus stars on the internal side of the glass pane in front of the prism.

I'll leave it like that as I don't think the fungus will spread any further. The whole thing looks quite old and the fungus needs food, moisture and warmth.

That doesn't exist here 😋
 
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But as it happens, I just found a DP-20 with heavy signs of wear on eBay. The LCD should therefore be ok.

A new project is announced: replacing the LCD in the DP-20 😎
 
Interesting repair report:

 
Be careful not to detach the conductive rubbers from the LCD and ensure that the LCD is then installed sideways. In my example I saw impressions of the contact rows in the conductive rubbers, which helped with orientation.

Erratum:

Be careful not to detach the conductive rubbers from the LCD and ensure that the LCD is then installed accurate to side. In my example I saw impressions of the contact rows in the conductive rubbers, which helped with orientation.
 
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Erratum:

Be careful not to detach the conductive rubbers from the LCD and ensure that the LCD is then installed accurate to side. In my example I saw impressions of the contact rows in the conductive rubbers, which helped with orientation.

I incorporated your correction into the original post for you.
 
The complex structure of the DP-20 viewfinder.

That's just too many parts. Makes me appreciate an old Exakta finder.

"Our life is frittered away by detail. Simplify, simplify, simplify! I say, let your affairs be as two or three, and not a hundred or a thousand; instead of a million count half a dozen, and keep your accounts on your thumb-nail." -- Thoreau
 
That's just too many parts. Makes me appreciate an old Exakta finder.

"Our life is frittered away by detail. Simplify, simplify, simplify! I say, let your affairs be as two or three, and not a hundred or a thousand; instead of a million count half a dozen, and keep your accounts on your thumb-nail." -- Thoreau

But the DP-20 can do many useful things 😌
 
Andreas,

THANK YOU so much for posting this. I too had the body LCD bleed, and after finding your post, I was able to replace my (from a donor body as well) LCD in 10 minutes. So, I joined the forum to say thanks.
 
Andreas,

THANK YOU so much for posting this. I too had the body LCD bleed, and after finding your post, I was able to replace my (from a donor body as well) LCD in 10 minutes. So, I joined the forum to say thanks.

Thank you for your feedback!

That's great, I'm happy about that!

I congratulate you! 😃
 
View attachment 363926

The LED, the small dot in the middle of the illuminator, is probably cast into the turquoise green mask.

You mention that "The structure corresponds to that of the Nikon F3(/T)". Would it be possible to replace the F3's "grain of wheat" incandescent lamp with the F4's LED? Looks like it should be about the same size.. And where would one source the F4 LED? I'm assuming Nikon no longer has them, but maybe find a suitable replacement? The intermittent finder illuminator on my F3/T "champagne" is a source of annoyance, and I've planned to fix it.
 
Would it be possible to replace the F3's "grain of wheat" incandescent lamp with the F4's LED?
You could replace a micro incandescent bulb with an SMD LED (something like 0805 size) and a series dropping resistor, assuming you've got enough voltage to work with, which I suspect is the case. A 0805 LED plus something like a 0603-sized SMD resistor will likely fit in the same volume as the original tiny incandescent bulb. Enameled wire can be used for leads.

Here's some people discussing the same: https://rangefinderforum.com/threads/nikon-f3-light-meter-illuminator-bulb-mods.176719/
They worry about the LED overheating but I've done similar things loads of times and those little LEDs really don't die all that easily from high soldering temperatures.
Also, there's some talk about "pro SMD soldering stations" (skimming quickly) and I can tell you that I've done a heck of a lot of SMD soldering work with a regular iron and a rather common 1mm round tip, which is also exactly what I'd use if I were to do this particular job. Yes, it does take some agility and practice to get it done, but $1 will buy you enough parts to try it a dozen times or more.
 
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