This Instructable will teach you how to identify, hack and use an old camcorder CRT viewfinder without the use of a service manual as those can be hard to come by (especially for older cameras). These little tubes are great for things like Heads Up Displays (HUDs) eg, wearable computers, and many other uses. They usually take standard composite video which is nice.
These viewfinders can usually be found on 1980's era camcorders and can be acquired pretty cheaply from thrift stores/flea markets/eBay.
I will put this here: CRTs contain hazardous voltages within and I will NOT be held responsible for your safety. USE caution when performing the operations outlined in this instructable.
Step 1: Materials and Items/Tools Required
The list of Items required for this
- Digital Multimeter or other device for testing continuity. (LED and battery work here).
- Variable power supply or standard ATX power supply (for figuring out supply voltage for the tube)
- Phillips head screwdriver (not shown)
- alligator clip leads for power supply and video source.
- RCA connector, color doesn't matter here.
- Source for composite video (in this instructable I will be using an old compaq armada)
- wire cutters/strippers
- that should be it for tools
- MOST IMPORTANT: THE CRT VIEWFINDER YOU WANT TO HACK.
Step 2: Opening the Viewfinder
Pretty self explanatory. Just find any screws and remove them.
The locations of screw holes can vary between manufacturers so the number/location of screws depends on your model/unit.
Step 3: Finding the Ground Pin.
To find the ground pin What you do is look for any component with a metal enclosure and touch one lead of the multimeter to there, then touch the other lead to the connector where the main cable comes in. Make sure the meter is set to continuity, EG diode test mode. The reading you are looking for in the meter should be around 1-2 ohms.
Step 4: Finding the Power Pin
To find the power pin, look for a nearby fuse or a thicker trace coming from the pins. mark these on the bottom of the board or write it down somewhere so you don't forget them because they are needed in the next step.
If the camera powers up still then just check the pins with a multimeter till you locate the power pins and check the voltage. write down any pin numbers/voltages before taking the rest of the camera apart. Do the above (first sentence) IF the camera wont power up. The displays do not have any voltage regulators as they are fed from the camera directly.
Step 5: Figuring Out the Voltage of the Viewfinder
This is relatively easy once you have found the power and ground pins. Connect your power source to the conncting wires that plug into that connector of the viewfinder and set the power supply voltage to its LOWEST SETTING. Once that is set, SLOWLY increase the voltage to 5 volts while watching the CRT. when the screen glows you have found the input voltage. If not, then increase the voltage till the screen glows. DO NOT EXCEED 12 VOLTS.
This is the part where you want to be careful as the CRT can contain high voltage.
Step 6: Figuring Out the Video
This step is relatively easy too. get an RCA connector and connect the outer copper to the video ground. This can be figured out the same way as with the power ground. Then connect the RCA connector to some device with composite video, an old portable dvd player works well. get the center white/yellow/red (whatever color is in your cable) wire and probe the rest of the pins till you see an image on the screen. When you see an image, write down the wire colors or pins.
Use caution here too with the CRT because of the voltage it produces ~500-1000V
see the image notes for the first image for my video wires. On mine, green is video ground and yellow is video in.
Step 7: DONE
Put the display back together and have fun. use it with a raspberry pi, or other things.
Hope you like my instructable. Feel free to leave any comments.