Hacking Camcorder CRT Viewfinders

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Introduction: Hacking Camcorder CRT Viewfinders

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.

3 People Made This Project!

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38 Comments

0
xanlexian
xanlexian

5 years ago on Introduction

I did something somewhat similar a couple of years ago. I used the B&W viewfinder CRT from an old camcorder, put a cheap-o "backup camera" for a car on it, put a IR LED ring around the camera, and have a small, battery-powered pocket night vision rig. I like to sit on my porch and see the critters in the woods at night :) I still use this little rig almost daily.

With the IR camera, I found the B&W tube works a lot better than the (seemingly somewhat rare) mini color viewfinder CRT's.

Great Instructable!!

0
devicemodder
devicemodder

Reply 5 years ago on Introduction

Also, nice job on the night vision scope :-) If this was reddit you'd get my upvote.

0
imark77
imark77

2 years ago

A few years back and many moons ago I acquired some nonfunctioning camcorders and came up with the idea of using one of the viewfinders as a monitor. there was a really compact one that I started with and couldn't get to work, so I moved onto another one which I was successful and have completed pictures of. it is so bright!!! it can also double as a miniature projector although the focus is a little bit tricky. I don't remember why I opted for SVideo input although I think I read somewhere that this particular model was S-Video ( upon further retesting it works either way although I think SVid gave a clearer picture signal… it may have been that during my testing of the camera output wire to a monitor it required an S-Video input to view ). I installed a power switch and I even figured out the wiring for the LED; that's not wired in as I can't decide whether I want a power indicator because the wonderful analog TV noise and bright screen is already obviously enough for me. maybe as some sort of indication down the road…. Hmmmm.

which brings me back around to my current thought process.

I recently started pondering the idea of getting the other compact one ( an Zenith PT. NO. 800-1159, 8v, 7w, made in japan, July 1991 ) going knowing a lot more about circuitry then I did 10? years ago. unfortunately I was pretty certain I would never find any documentation I made many years ago ( I've since moved to digital documentation it's so much easier! photos and/or a text file with some sort of relevant name and date and maybe even in a folder of its own off a projects subfolder. ) so I needed to figure out again which one was the power pins without digging into my scrapyard. I didn't think the metal casing of the HV transformer would be connected to ground but sure enough DUH!!! it was. and now that I figured out the ground pins the positive was next and of course fused and I was off and running and with only 4 wires remaining it was quick work to find the video pin ( I took longer because I was quite fascinated with the ground loop I was inducing just by touching the video pin ).

it has 7 pins of wires, 2 grounds Brown and Black, one positive thankfully Red, one video White, and the remaining 3 wires are Yellow Orange and Gray and are some sort of output signal generation and I would love to know more; I think I managed to get my multimeter to read out 60Hz on one of the wires.

being that this model is 8v, With more electronics knowledge now and having an adjustable power supply ( EBay $15 module ) made things a lot easier than many moons ago when I think I tried to power it with a relatively close 9V battery or 7.5V worth of 5x AA's and got nowhere.

I have determined that it will run on 7.5v somewhat unhappily, so I am not sure whether I blew the fuse or if it was damaged prior to my acquisition. so now knowing that it was a fuse and it was indeed bad I did the horrible!!! temporary bypass!!! ( of course with a 700mA limit on my power supply. this thing is pretty efficient as the amperage draw was 0.07mA@8v ) and I managed to create life.

so I now know it's a 250mA fuse that needs to be replaced but I don't know whether it's fast or slow blow because I am having horrible trouble tracking down the datasheet for the ceramic "SOC 250" ( I wish manufacturers would put an "F" for Fast, an "S" for Slow and an "N" for Normal ).

once i know the correct fuse to order I will add it to yet another eBay order with an adjustable boost converter with a micro-USB connector. my thought process on assembly is to take the boost converter and sandwich that with another board of connectors. Video in on an RCA and 3.5mm T_S Mono, Power and Video output to monitor on an 3.5mm stereo TRS to allow remote location of the power unit and easy extension with headphone extension cables.

P.S. the Windows 98 startup screen which is by far my favorite of all the windows must be burned into my brain because I thought that the image was in color as well, either way it stuck out like a sore thumb on image searches trying to find more information.

Zenith PT. NO. 800-1159.rtf.001.pngZenith PT. NO. 800-1159.rtf.002.png
0
imark77
imark77

Reply 8 weeks ago

So one of the few things I got done this year and partially last year I managed to get mine working. Turns out the fuse was blown and took a good long time to find a replacement fuse. I Assembled all the parts I wanted to put together and then it sat on my shelf for a year. So out of a brief necessity to distract myself from life in 2020 (not corona it's been a bad year) I force myself to do a project and it came out really nice and I need to post pictures.

0
retro_person
retro_person

7 months ago

Great Instructable! One question though: I have a 0.5" viewfinder CRT that is quite packed in and whose circuit board is stuck underneath the actual tube, which I can't remove. However, I found a 1.0"-1.5" CRT viewfinder on eBay for a good price, similar to the one pictured here, and has a larger circuit board that is more accessible and has larger parts that are easier to discern. Which one would you recommend to modify?
Edit: Also, my CRT also has a special flat ribbon connector that is used to connect via proprietary cable to camera. The connector jack on the CRT has four leads coming off, the rightmost one having a thick trace from it to a small capacitor(?). Do you think that the thicker trace could be the power pin? Also, I'm slightly confused: If the power ground and video ground can be found in the same way, how do you know which is the power ground and which is the video ground?

0
imark77
imark77

Reply 8 weeks ago

if you end up with two wires that link to a ground then it doesn't really matter. Generally just pick one or tie them both together. Sometimes the color of the wire could help distinguish which is which like if it was a green or black.
The thicker trace is probably a power trace especially since it's going to a capacitor which can tell you which way around is positive and negative.

0
600017659
600017659

Question 2 years ago on Introduction

Would there be a way to get the signals that are going into the viewcam from the camera and turn them into av?

0
imark77
imark77

Answer 2 years ago

Theoretically it will either be a composite or svideo signal which may or may not like being "y'ed to more than one sink device. And it may or may not be a color output. I believe I saw it mentioned somewhere to use an external monitor as a method to find which pin outputs the video. however if this is an LCD based viewfinder it is going to be a digital? Signal of some sort FYI.

0
devicemodder
devicemodder

Reply 1 year ago

>however if this is an LCD based viewfinder it is going to be a digital?

I have a side flip out screen i pulled from a broken camcorder. this particular one takes composite video.

0
nsteffanov7
nsteffanov7

Reply 11 months ago

The LCD on the broken camcorder I got the CRT from takes YCbCr which is interesting, seems like it'd be harder to drive as it needs a few other things according to the schematic

0
imark77
imark77

Reply 8 weeks ago

Well that's interesting.

1
microcarguy2006
microcarguy2006

1 year ago

My VHS camcorder has got many years left in it yet lol... Would be cool to do this though.

0
imark77
imark77

Reply 8 weeks ago

It is pretty cool but it's also pretty easy to find a donor material if you get my drift ask around for old cameras from family, friends etc.

0
uncleunvoid
uncleunvoid

Question 1 year ago

Would like to get incontact with someone who has executed the above (maybe even the author him/herself.). Please reply to this.Simple questions: Is there a way to miniaturise the electronic board these days? Is there a difference between US and european devices do do the above? I am trying to use a TV camera viewfinder color about 5" Are the connectors or anything different than to camcorders? Cheers.

0
imark77
imark77

Answer 8 weeks ago

Let's see if I understand this question correctly you want to miniaturize the board more? I think if it's a miniature viewfinder you're going to be as tight as the clearances are on the high-voltage side of things anyway. Maybe/unlikely.
Difference between US and Europe would be three 50/60 Hz difference and TV signal formats.

0
nsteffanov7
nsteffanov7

11 months ago

Using a Sony Handycam CRT and the image keeps scrolling, like the Vertical hold is off. Any ideas?

NVM - It turned out I had flipped the video signal and the ground while soldering. It works but it's pretty blurry, I even compared it to the viewfinder of a similar model handycam and it's way blurrier.

NVM yet again - I switched and tried to USB power it and that got rid of the blurriness!

0
RavinduV
RavinduV

Question 1 year ago

When I did the test , it beeped for 3 pins including the thicker trace. What might have gone wrong?

0
devicemodder
devicemodder

Answer 1 year ago

probably other paths in the circuit.

1
conundrum2142
conundrum2142

1 year ago

Hi. Incidentally if anyone has a non working unit please feel free to send it in my direction.
A lot of the time I can fix these and parts are hard to come by especially the (expensive) LSI IC.

Also some recent camcorders eg the miniDVD sort have what seems to be a colour sequential LCD because it has the rainbow effect. These are a lot better than simple B/W units as can be driven at higher speed but these typically can also be used with a -11 to -18V supply in addition to the usual +3.3 and +5 needed.