Introduction: Mini TV / Oscilloscope

Picture of Mini TV / Oscilloscope

Hi, I'm going to show you how to make a tiny TV/Oscilloscope. You will be working with a Cathode Ray tube which requires high volts and high pressure vacuums, so be careful. To build this you need patience.

Please rate my instructable or leave questions. They will be answered.

This is an old instructable I accidentally deleted a while ago and managed to find via a link deep in the interwebs. The TV has since been lost, but I plan on making a new and better one.

Step 1: Get All the Stuff

You will need...

+ A soldering Iron/Gun*
+ Solder*
+ A small phillips screwdriver*
+ A Hot Melt glue gun
+ Hot Melt Glue
+ Scissors

Electronic Items:
+ 3 DPDT switches*
+ Reasonably thin wire*
+ Two nine-volt battery snaps*
+ A Relay*
+ An LM386 audio amplifier IC*
+ A 100k Potentiometer*
+ A 10uf Capacitor*
+ A Small Speaker*
+ Female AV Jacks°

Other Items:
+ An old video camera {circa 1990}
+ A craft box to build it in

*can be bought at radioshack etc.

Step 2: What Are These Dohickys?

Picture of What Are These Dohickys?

Before you get started, you will have to take apart the viewfinder/microphone. Pretty fun actually. Pictures are here to help.

Step 3: Get Out the Important Part

Picture of Get Out the Important Part

Take out the video section of the viewfinder. Don't break any wires or anything and be very careful not to get shocked. Capacitors inside may still hold a small charge. Also, don't break the screen for christ's sake.

Step 4: Identify the Connections

Picture of Identify the Connections

This is frustrating. You have to figure out what is power in and video in. Hook up a nine volt to random wires to find out. If the screen lights up, you have found the power input. Once that is found, add more wires until some garbage appears on the screen, that's video in. Mine came out like this...

Step 5: Build and Connect

Picture of Build and Connect

Have fun. Think, Cut, Solder, Sweat, Get Burned, Yell F*ck, Stomp around, Rest, Build, Freak out when it don't work, Cry, Scream, Pee, Wash Hands, Build, Get it Done, Then realize you forgot batteries.

A pictorial of the layout is below. The wires are obviously not 'connected' to the batteries, the 9v battery snap however, you get the idea.

+ On the LM386, the side with the indentation is top. Very important.
+ The colors of your coil wires may be different. It is trial and error. Go to for more information on coil hookup.
+ Taping wires down makes it easier to move around.

Step 6: Mount

Picture of Mount

Get the glue gun ready and build a thingamabob out of the craft box to make it look nice. It also may be a good idea to cut a hole for the screen...


rbusch (author)2016-10-27

That's pretty sweet! i love those little CRT's. a few month's back i made a Mini CRT Pong game and its a two player (if you don't mind smashing faces together to try and see the screen) :)

RyanS280 (author)2016-08-02

I obtained one of these (20mm) from a Canon Digital8 tape camcorder recently, and a few others over the years, IF you do this, be warned, many of these take more than one input type and voltages, 5v for digital parts, 12v for small flyback+H/V Coils.

Also, most camcorders from the 80's or 90's have an onscreen display generator (batt, tape time, status, etc..) some have them in the viewfinder as was the case for my Canon E708, its viewfinder drive board contains a character generator chip, and takes 8N1 ASCII serial data input 1200bps.

I plan to use two of them for my quadcopters FPV video, the OSD generator in the unit will be connected to an Arduino unit that recieves my telemetry signals, then displays them onscreen

Jfieldcap (author)2016-06-21

Neato! I've never thought that there might be a mini composite CRT in old cameras like this! I've seen plenty in thrift stores and passed them up as "worthless junk", but knowing this...

Electrospark (author)2014-09-10


I just made one and it work's pretty well! :)

Thanks for the information!

Josehf Murchison (author)2013-07-16

I like this.

I never thought of that as a source of a cathode tub.

Have you seen my Instructable, Building a Digital Oscilloscope from a DIY Kit?

aaronXtreme (author)2012-07-21

this rocks

spystealth1 (author)2012-03-03

Wow! I'm pretty sure I found an old video camera just like that in a thrift store.

bmarshall-2 (author)2011-03-26

100k pot for the gain adjust on your LM386, are you sure?! do you mean 1k?

kikazz (author)2010-10-14

I apologize for my rudeness... I should have been a little more thoughtful with my remarks. and hey, im starting to spell bad too. Sorry.

grenadier (author)kikazz2011-01-05

No problem, I used to use IE back then. IE had and still does not have a spellcheck.

kikazz (author)2010-02-07

pleeeeeeeeeeease learn to spell. it really is annoying. thanks

El Mano (author)kikazz2010-04-12

Forgive me, but part of spelling is capitalization. Good job with the punctuation, though.

It's so funny when people post indecipherable garbage. It really reflects their personality.

12V (author)2010-02-05

i took apart a camcorder and found a crt with a 16mm screen and 6 pin base + a psu (2,200v) as well.
for brightness try adjusting the trimpots
e.g. those blue things with a screwdriver.

12V (author)12V2010-02-05

try putting a 4.7-10 uf cap on the output of regulator  (mightprevent/reduce picture shrinkage)

luudvig (author)2009-11-22


uskmrules (author)2009-10-12

 hey can u take a picture of the board where ur power wires and video wires connect to the tv board. i cant find the wires.

dark sponge (author)2008-11-27

You could use 6 rechargeable AA batteries. It would last longer and would supply enough power for the sound and the picture at the same time.

grenadier (author)dark sponge2008-11-29

No; I have used a car battery and the same thing has happened.

ReCreate (author)grenadier2009-10-04

Then the problem is not lack of power....

12V (author)grenadier2009-04-10

can't you use a separate voltage regulator for each circuit. and a will charged battery.

dark sponge (author)grenadier2008-11-30

That's weird...

okura (author)2009-10-03

Unbelievable.....a KID of 13yrs has SO much electronic savvy, so much vocabulary, so many tricks???? ...have seen many child prodigies and have mentored some myself, but this guy beats them all !! Either he's a miracle or a well planned hoax. Wish it isn't the later though...... I wish him good luck and Gods very best!!!! PS: wish there are ( I'm sure there are ) more kids like him around, too!

latobada (author)2007-07-22

i think the fact that because you don't want to take pictures, just takes the instructable down on so many levels. i mean it is quite original, and heck, i probably wouldn't be able to make it. but if you have the means to, and the time (it would be quicker to take a picture and draw-on or even use the box feature on instructables, than to draw it by hand) i think that the final result of would of been much more professional.

On a second note, this is from a point of view of me trying to figure out how this was built, im just going to say that i am having a hard time following instructions, such as in step 5, i have no idea what i am connection, to where, and from where.

Everlong (author)latobada2007-07-22

Hey latobada! I agree with you about the lack of photos, it's kinda hard to figure out whats going on. Basically this hack is not really a mini TV hack at all, its a mini video monitor hack. These old camera viewfinders are simply tiny video monitors that will display a composite video signal (the kind you get out of a DVD player, VCR, or the side of a video camera). They are normally constructed with three wires leading into them, a positive power lead, a common ground, and a positive video lead. All you have to do is figure out which leads are which through trial and error, then hook the positive power lead, and the common ground (the negative lead) to a power source, and then hook up a video source to the positive video lead, and also the common ground lead, and you should get some sort of image on the screen. Also, in step 4 of this instructable, Googfan recommends hooking up a 9v battery to test the leads, this might not be a good idea as in my experience these monitors seem to run on 3v-6v, but you can find out for sure by taking a reading off the original camera output. If the video appears fuzzy or dim, you can normally adjust it by turning the mini POTs the should be somewhere on the driver board, on Googfan's step 6 they are the two little blue things just under the screen. Anyway, here are some photos of an old effort of mine, running off an old motorola phone charger, and displaying the output from my DVD player.

Tazom (author)Everlong2009-07-30

dude! i have almost the same CRT viewfinder and i cant get it to work, can you contact me about which cables and etc etc.!!?!?! PLEASE!

kishida (author)Everlong2007-09-06

Hi, I've also got a b&w; crt viewfinder in my misc. box of stuff and I'd like to use it as a video monitor. It came out of a Sony CCD-F70 camcorder and has 4 leads. How do you figure out which wire is which through trial-and-error? Thanks.

grenadier (author)kishida2008-01-20

srry bout the delay, hook random leads to random battery leads, things should happen. btw, my instructabe got updated

grenadier (author)latobada2007-07-23

I already bult the tv and did not want to re-take it apart to take pics

latobada (author)grenadier2007-07-23

you could of done zoom-ins

grenadier (author)grenadier2007-07-23

also the step 5, you need a knowlage of circuit schematics.

grenadier (author)2008-01-20

yes grnd> -bat ground on vid cable is usually the 'hairy wire'

Aleksaa (author)grenadier2009-07-15

seriously now that it really works or not, and is used as osciloscope?

Aleksaa (author)Aleksaa2009-07-15

just as in the picture, and who I make it just the same as in the picture and work? my viewfinder has only 4 pin.2 are the power and other 2 I do not know

grenadier (author)Aleksaa2009-07-16

yes it should. so you found the power? good. thats tha hard part. one of those other two is video signal in. Cut a composite (yello) video cable in half and strip the wires. Attatch the shield (outer wire) to negative on the tv and power it up. plug the video cable into your xbox or something. now, try touching the center wire of the video cable to one of the two unknown wires. whichever one works is your video in.

aleksa (author)grenadier2009-07-16

i done that and shows static.The viewfinder is from an old vcr blakpount cam....:(

grenadier (author)aleksa2009-07-17

OK, the one that shows static is video in. you need to make sure it is securely connected to get a picture, like soldered. then if it is still staticy, look for potentiometers on the circuit. they look like plastic screws. turn them while the TV is on. if you keep fiddling with them, eventually you should fin the sweet spot and get a picture. one is brightness, one is focus, and one is v-hold. there may be more. even better. is the video signal you are trying to put in NTSC? PAL or SECAM will not work.

aleksa (author)grenadier2009-07-18

you are only 13 and you are a GENIUS...its working...!!!

razieltehawesome (author)2009-03-30

how would you make this just a tv and no oscilloscope?

aleksa (author)razieltehawesome2009-07-16

i done that it shows just static.....damn : (

razieltehawesome (author)2009-04-01

thanks so much I can't wait to get the parts in, this will be both fun and educational on many levels, you had a link about the coils but the link is down, is there any other way I can learn the setup or something similar? I bow to your intellect,

Hmm, the link's down?.

when i click on the link it says "Sorry, no posts matched your criteria."

thats odd. ill post a new link when i find one.

ok cool, what would I need to search to look it up on my own?

"tv oscilliscope"

dark sponge (author)2008-11-30

But that shouldn't happen if you use a bigger battery.

grenadier (author)dark sponge2008-11-30

well id does for some reason.

The 4th Doctor (author)grenadier2009-03-07

I believe its because when the audio circuit is drawing power it steals voltage from the video circuit making it so although the powersource can supply the amperage the tv circuit isent getting the voltage to do so. ohms law ftw!

But that shouln't have happened when he used a car battery. Something else must be going on because it would have to draw tens (or even hundreds) of amps for this to happen with a car battery (which he said he tried).

Its the voltage the battery is capable of supplying the current but its voltage is divided up upon the 2 circuits spreading it thin it is kind of odd though that the video circuit has trouble when its rated for 5 volts maybe its just how much audio fluctuates

About This Instructable




Bio: Physicist
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