At first, identify your slide projector: if you have an old model without an airflow channel in front (see picture), you might need to be creative to get the cable connection running in a nicely manner. If you can, go for a newer version.

To remove the slide holder from the projector, just move it upwards.

Now we take a very important safety measure to stop your display from being destroyed by ripping the flat cable in half by accidently moving the slider. Do it now, or you will regret it later. Pull the slider in either direction so it is in an end position. Now drill a hole (3mm) through the holder on the other side. I drilled two holes to make it look even, but you need only one to keep your slider fixed.

The LCD screen used for this project is a 2.0" PAL/NTSC panel from Adafruit (Adafruit 911). You need to remove the backlight in this step.

Be very careful with the display, especially with the film cable, it will rip easily.

If still connected, remove the display from the board by opening the connector. Detach the display.

The display has a silver metal cover. Remove this cover. Remove the white backlight carefully. You have to cut the smaller film cable that is connected to the larger one by two large soldering spots (it's for the backlight power).

Remove all foils that come down in this process. You now should have a simple shine-through display. It has a matte side and a silver side.

A word of warning about the Adafruit 911 displays: these gave me some (expensive) headaches, so I will share my experience with you:

• respect the warning on the website: the film cable is absolutely delicate
• the devices work with input voltage of 5V to 12V
• there are two buttons on that PCB (see picture): one is next to the white connector, the other one is on the opposite
• the one next to the connector rotates the screen
• the one on the opposite changes the contrast of the screen
• both buttons keep their settings after a restart
• obviously, there are different versions of the PCB AND the display around: the website states, there is only one button (to change the contrast). This is not true for the current PCBs, they all have two.

I made the mistake of interchanging displays and PCBs, which turned out to be a nightmare. Do not do this! The PCBs and displays seem to have different specs, I fried the power regulator of one PCB with 12V input voltage, one display did not rotate and had image distortions, for example. After I found out about this, I compared three PCBs with each other and all of them had different parts soldered or some parts not soldered.

You should make sure your display is ok with a "dry-run" before dismantling it (or shelving it for later use). As a video-source, you need a RCA (FBAS) device. Canon EOS cameras have a RCA (FBAS) output. Just note, that it turns off very quickly. But for testing, it's ok.

If your display does not rotate, you will be very limited in the devices you can connect as it needs to be able to rotate the RCA/FBAS ouput itself. The Raspberry Pi can, but most other devices can't!

Take an old/unused slide and open it (you should use a very simple type that has no hinge). Measure the size of the slide and cut out a piece of cardboard.

Now take the display, center it on the cardboard (so the display is in the center) and cut out the cardboard so you have a simple spacer for the slide.

Take the cardboard, glue it to one side of the slide, put the display in and glue the other of the slide on top (you don't need to destroy the slide, I did it by accident).

Now take the slide holder and get a plier. The slide holder consists of two parts that slide into each other. Separate them by pushing a small metall bolt in, then you can separate both parts:

Now take the outer part and bend the upper hinge a little upwards (double check which hinge is actually the upper hinge!). This needs to be done as we can't put the the inner part back sideways but need to get it inserted vertically. Don't bend it too much.

Now insert the LCD "fake" slide into the inner part as you would insert a normal slide. Make sure it's in the correct holder (left or right depends on your drilling holes). The silver/metallic side of the LCD must face forward.

The film cable fits through the opening on the bottom, but needs a bit of pushing by a toothpick or something.

Insert the inner part of the holder in the outer part and push the film cable trough it, too.

Now don't do anything else, but INSERT THE SCREWS INTO THE HOLES AND FASTEN IT. Otherwise, you WILL destroy the film cable by accidently moving the slider!

I did this once and it was not cool to see 35$ literally ripped in half.

Shorten the ZIF double connector:

Now attach the ZIF double connector and the ZIF cable:

Unmount the hole objective thing from the projector (how to do this, depends on projector design; you can leave it in place if it's too hard to remove if you have an old projector design).

Remount the slide holder into the objective by pushing it into the holders. If it hangs, don't push too hard to avoid damage but check the length of the screws. With M3x10 it's a perfect fit if you use normal nuts. Special nuts were too large. As a workaround, remove the screws and mount them "reverse", e.g. the nuts are facing forward then. 

Push the ZIF cable carefully through the ventilation channel opening of the slide projector and it remount the objective.

To install the PCB, take the unused plate, remove the glass and drill two holes to hold the PCB.

Take the spacers and install them. You need spacers with nuts or you can just use screws and print some spacers with your 3D-printer (https://www.thingiverse.com/thing:1656609).

Install the PCB onto the spacers. It's direction is crucial: the ZIF connector needs to face downwards, the whole PCB is mounted "backwards". This is to avoid the ZIF cable to twist. Just see the picture:

The Adafruit 911 display's PCB has a small pigtail coming with it that has a red, black, white and yellow wire (the latter soldered to a RCA/FBAS connector). The red and black wires are for the power connection. If you plan to just use RCA/FBAS with nothing else, you can solder the red and black wire directly to a female Molex connector to the 12V pins (yellow/black) - or whatever you chose as a system for your internal power connectors.

If you plan to install other components that need 5V, e.g. a Raspberry Pi, ESP32 or Arduino, you should run the Adafruit 911 PCB with 5V. I used a BEC module (Battery Eliminator Circuit, a very small switchtng voltage regulator). You can also use a linear power supply, both have advantages and disadvantages (https://en.wikipedia.org/wiki/Voltage_regulator#Comparing_linear_versus_switching_regulators). You attach the input of the voltage regulator to 12V and connect the output to the components that run with 5V.

Attach the ZIF cable to the ZIF connector (double check the correct direction) and the 4-pin-connector to the Adafruit 911 PCB. For testing, install a source to the yellow RCA/FBAS-connector, a Canon camera for example. The display itself does not display anything without a working source.

You should not install the plate for testing (and calibration), so put it on top, but make sure to shield yourself from the bright LED and the PCB from a short circuit. Turn the power on and you should see the display flicker and show content.

Now use the button next to the white connector to change the orientation of the picture and the button on the opposite side to change the contrast. Use a picture to make the contrast look good - the menu of the Canon camera will mislead you, use a real picture for this.

Now install the plate in the very first slot in the projector. You did it! - Enjoy watching Video input on a Retro slide Projector!

For further ideas, there will be a third tutorial.