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.
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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...
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Electrospark7 months ago


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

Thanks for the information!

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?
aaronXtreme2 years ago
this rocks
spystealth13 years ago
Wow! I'm pretty sure I found an old video camera just like that in a thrift store.
bmarshall-24 years ago
100k pot for the gain adjust on your LM386, are you sure?! do you mean 1k?
kikazz4 years ago
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)  kikazz4 years ago
No problem, I used to use IE back then. IE had and still does not have a spellcheck.
kikazz5 years ago
pleeeeeeeeeeease learn to spell. it really is annoying. thanks
El Mano kikazz5 years ago
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.
12V5 years ago
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 12V5 years ago
try putting a 4.7-10 uf cap on the output of regulator  (mightprevent/reduce picture shrinkage)
luudvig5 years ago
uskmrules5 years ago
 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 sponge6 years ago
Why are you using two 9v batteries? You could just use one. Better yet, use an old 9v wall adapter.

(by the way, I'm 13 too!)
grenadier (author)  dark sponge6 years ago
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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 sponge6 years ago
No; I have used a car battery and the same thing has happened.
Then the problem is not lack of power....
That's weird...
grenadier (author)  dark sponge6 years ago
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But that shouldn't happen if you use a bigger battery.
grenadier (author)  dark sponge6 years ago
well id does for some reason.
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
The amount of current a battery can supply is not based on it's voltage, but it's internal resistance. Bigger batteries (like car batteries) have a lower internal resistance, so they can supply a greater amount of current.
grenadier (author)  dark sponge6 years ago
It seems to go away when i use a switching power adapter. Not a transformer adapter though.
12V grenadier6 years ago
it's because they use voltage regulators.
The maximum current is limited by internal resistance yes but the voltage/resistance determines how much current Does flow in a given situation every battery max's out somewhere but the current it supply's to a given situation is changed by its voltage and the loads resistance Anyways audio fluctuates CRT's seem to get affected from pretty small changes, my TV flashes a bit when i turn stuff on/off i suppose the video circuit probably doesn't even have a filter capacitor I shall leave it at that
12V grenadier6 years ago
can't you use a separate voltage regulator for each circuit. and a will charged battery.
okura5 years ago
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!
latobada7 years ago
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.
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 Everlong5 years ago
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!
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)  kishida7 years ago
srry bout the delay, hook random leads to random battery leads, things should happen. btw, my instructabe got updated
grenadier (author)  latobada7 years ago
I already bult the tv and did not want to re-take it apart to take pics
you could of done zoom-ins
grenadier (author)  grenadier7 years ago
also the step 5, you need a knowlage of circuit schematics.
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