^Potentially... If i remember correctly horizontal is 15 khz and vertical is 60 hz (mains frequency).

For now I will just use it for "oscilloscope music". Check out Jerobeam Fenderson on Youtube. He does phenomenal stuff vectorially drawing graphics with sound. I hooked it up to the sound system yesterday. Coils are 2 and 14 ohm each. Speakers are 6 ohm each. It kind of works but needs some tweaks to display things correctly.
Will post a vid as always, when it is done=)
Also I found RGB bias knobs at the back to make the screen any color. Turned it sweet scope-green for now.

After a recent and rather successful trip to the recycling area, I found and old GE CRT TV (tiny one) with a vcr and a blockbuster batman tape stuck in it . I cannot imagine who would keep something like this until friggin 2019 but thats besides the point...

I was always a big fan of CRTs, and I was wondering how can I hack it into something cool. And by "cool" I mean being able to control the video signal in some manual and interesting way.

Decades ago back in school I have done the classic hookup of sound output to deflector coils to draw Lissajous figures and I tried building a crude scope as well... I want to take this in some sort of NEW direction, maybe somehow control the color?

The other thing I have is an Arduino and I have several programs with TVOut library (I wrote code for pong for example), which works via composite input. It is BW only, but maybe something can be done about it.
Wondering if anyone has any unusual ideas!

This immediately reminds me of youtuber "PhotonicInduction" who does all kinds of very odd things with crazy parts like that!

Alrighty... while the next video is being cut I'll share these, hopefully new insights.

I received my new 2 kg crucible. I chaged the coil to a 5 turn coil. This time, I WEIGHTED the crucible before use so I can see how much graphite is lost. And, it seems, a lot! After an hour runtime a 234 g crucible lost 25 grams of graphite. And I can confirm with absolute certainty that power draw depends on amount of graphite - it was at a healthy 1083 W with newly inserted crucible, and by the end was about 970 w as graphite was lost. I will not be surprized if for my next melt I will start with those 970w. The amount of material in the crucible seems to have insignificant (although measurable) effect on power draw.
So this creates a practical problem. I do not want to pay 15-20$ for a new crucible every ten melts. Also, even bigger problem is that with a tiny crucible it is very inconvenient to remelt things you have casted - you d have to laboriously cut it up in small pieces.
A truly useful crucible should be at least the size of cookie tray ingots, and good for many melts.

So, my next R and D will be devoted to being able to manufacture crucibles with clay/plaster/sand/whatever mixed with graphite. There got to be a recipe somewhere. Or switch to steel container, but I have no idea where to get something with thick walls.
Another idea is two concentric pieces of pipe acting as a heat jacket. Loose graphite can be put between the cylinders and replenished as it burns out - to keep power output consistenly high.
But at that point, I might as well design a regular electric kiln that will not have those ridiculous problems with small impractical crucibles, constant power draw issues due to burning graphite and all other sorts of maintenance that come with the iduction setup.

Anyhoo, the new vid is coming!

Molds: I use 50/50 plaster / sand mix, also 2 plasters for 1 water. Found information suggests that pure plaster cannot stand heat shock very well so sand makes it softer (although weaker) so it doesnt crack. Oven treatment is super neccessary so the mould doesn't explode on contact with hot metal from steam forming throughout. (it dries for couple days too before that but it is not enough)
Pure sand casting doesnt have this issue, but it is a chore to work with. I ve used it in the past for my other propane vids.
Transformer would hum only slighlty louder on overload. The massive fan under it drowns any possible sounds. It is not a part of the system in any way and connects separately to mains power.
The shunt does nothing at the moment. Crappy ebay meter burnt out and i left the shunt until I get a new one. As I explained in the description, to measure DC current just divide power (blue meter) by DC voltage (orange multimeter) (aka 700w/46v=15a dc.) So I have about 15 amps dc going in the induction unit. It can also be calculated the long way by utilizing turn ratios on transformer and ac current on mains, but thats the long way.
The hot metal is yellow to white, and is quite bright. It even shine through thick insulation. It loses brighness quickly when crucible is extracted.

So basically now I am going to wait until i get another different crucible from ebay (also ammeter). If i see increased power with new crucible, it will be conclusive that graphite is responsible for the most power draw. 
Meanwhile I may cut the existing crucible in half and plug a small coil, see how that goes. 
 

Finally!
The dagger didn't turn out pretty but the rest works okay. Hope it answers some questions!

There wasnt much dross, copper was clean, mostly from av cables. Coil has a diam of 12 cm and something like 16 turns.
Here is my youtube channel where I melt some aluminium with my other diy propane kiln (sword and ingots in another one). When I finally get to make an induction video will post that on there too.
/>Also, on unrelated note, the epic power plant tour vid may be of interest to high voltage enthusiasts... but thats a different story...

Hightemp:
Well, the way I see it, power output will determine how quickly you heat things up and WHERE the thermal equilibrium is reached - aka power IN starts being equal power OUT.
It is also determined by losses. Even if energy is pumped in at a slower rate, but you somehow can magically improve insulation, you will reach equilibrium at higher temperatures. The other thing to note is, exponentially more energy is required to raise something to a degree at higher temperatures than at lower temperatures (relative to outside temp that is). That fact was especially evident with my other-other pottery kiln which lights up an LED when SSR is on so it is easy to see the difference.

You can reliably melt about 3 kg s of copper with about 800 W. I will be doing further tests + casting via lost PLA method soon ish, will have real numbers. It is funny how i started thinking like a scrapper a bit - always checking if there is some copper laying around somewhere haha.
peterspaco: I nearly doubled the coil so it covers full crucible. Power stayed nearly the same, even decreased a bit. Frequency has halved. I think the only way to increase output is to change diameter that can't be done currently with my setup.
To kind of summarize it (correct me if i am wrong) but MORE power is drawn if we have:
Lesser coil diameter
More material inside the working volume
Higher frequency
Less turns in the coil

 

Peterspaco:
I might try the thinner insulation, but the one I have is quite amazing. May be losing some efficiency with a thinner one.
Idle current: looks like i forgot to record it with the latest setup. will have to get back with that.
Crucible wrapping is one thing i didnt think of. Will try that next!
I hope to cast bigger things so even a 3kg crucible is too small. I made a whole sword with aluminium when I ran my propane mini kiln!

 

I work at a library and here we have not only SnapCircuits, Mbots, but also Arduino kits that can be checked out home. It may be for a bit older kids, but some do know basics of programming at a rather early age!
Also it is good to teach kids 3d design, it is a real useful skill. Lots of adults seem to have very little spatial awareness which i find kind of funny. Tinkercad for the win!