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LAN_403

Atomic Parts

Fri Aug 08 2008, 02:17AM

Registered Member #1591 Joined: Wed Jul 16 2008, 06:34PM
Location: Livermore Ca
Posts: 14

Here is a simple (early version) of a homemade CRT that I made over the period of several days. It consists of a 250 ml vacuum filtration flask as the target chamber, a modified test tube as the electron gun, phosphor from a fluorescent tube, and a GAMMA regulkated HV supply. Vacuum is supplied from a two statge Yellojacket vacuum pump. The magnetic deflection consists of two solonoids and currently there is no focus anode (yet to come).

I have attached a couple of pictures and a link to a very quick and dirty youtube video of the project. Also linked on the youtube video is Nyle Steiners "Vial" CRT's. All are quite interesting.

Mark

Ultra7

Fri Aug 08 2008, 03:34AM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

thats pretty cool!

Hon1nbo

Fri Aug 08 2008, 04:09AM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040

Nice Job!
and good idea to use a vacuum filtration flask... any idea what the pressure inside of the tube is?

uzzors2k

Fri Aug 08 2008, 10:26AM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

That's incredible! Connect some signal generators to the deflection coils and make some patterns for us. This tops my list of weekend projects.

Myke

Fri Aug 08 2008, 05:47PM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Ooo, really cool. I noticed that in the beginning you just kept the spot in one place which burns the phosphor. You can see that it's burned when you sweep over it because it's not lighting up as well. Just keep the intensity down when it's a dot and you should be fine.

Hazmatt_(The Underdog)

Fri Aug 08 2008, 07:39PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

That's really sweet man! I want to do this too for an educational demo for kids. You just need some amplifiers and you'll have an oscilloscope, hehe.

aonomus

Fri Aug 08 2008, 09:01PM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

Wow, never would have thought of using a filter flask.....

How did you transfer the phosphor coating from fluorescent tube to flask?

reign

Fri Aug 08 2008, 11:26PM

Registered Member #260 Joined: Sun Feb 26 2006, 09:51PM
Location:
Posts: 17

aonomus wrote ...

Wow, never would have thought of using a filter flask.....

How did you transfer the phosphor coating from fluorescent tube to flask?

From what I have read in the past, you can mix the phosphor coating from the fluorescent with water (I think) and leave it sit in the bottom of the flask. When the water evaporates the phosphor is left behind and coats the glass.

I may be incorrect, though. I am just working off of memory here.

Atomic Parts

Sat Aug 09 2008, 04:42AM

Registered Member #1591 Joined: Wed Jul 16 2008, 06:34PM
Location: Livermore Ca
Posts: 14

Thanks all for the comments.

Since I have built the thing, I have noticed a major flaw which has greatly reduced its operability. Sputtering. My glass electron gun became seriously cluttered with copper deposition. Thus, the beam current began to skyrocket and the gun began to get hot. Also, as predicted, the beam intensity slowly dwindled to a very faint dot. The remedy is to build a new gun with an aluminum or stainless steel anode and cathode. That would be about a one day project since the target chamber can be separated from the gun chamber via the homemade flange.

Reign was right. Once the phosphor is collected from the donor tube, just mix it with a little distilled water, get it to settle on your chosen face plate in a uniform manner and let it evaporate.....SLOWLY. Dont try to accelrate the drying process. It will surely flake and look messy. Furthermore, a little goes a long way. What may look like a very opaque to transparant film when wet will dry to a nice solid white facing when dry.

I suspect that if you mix a very VERY small amount of copper salt (copper sulfate?) with the phosphor, it will glow blue as opposed to white. Something to experiment with.

Specific to the vacuum, I guess its hovering around 20-30 microns.

Once I have a stable design, I'll hook up the signal generator and post another video. Right now, I am trying to reduce a jpg to a suitable size for posting.

Mark

aonomus

Sat Aug 09 2008, 05:15AM

Registered Member #1497 Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801

For the electrodes you could try taking the emissive coating off of fluorescent tube filaments and using that to dope the filament that you are using maybe.

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