Homebuilt Cathode Ray Tube
Atomic Parts, Fri Aug 08 2008, 02:17AMHere 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
Re: Homebuilt Cathode Ray Tube
Ultra7, Fri Aug 08 2008, 03:34AM
thats pretty cool!
Ultra7, Fri Aug 08 2008, 03:34AM
thats pretty cool!
Re: Homebuilt Cathode Ray Tube
Hon1nbo, Fri Aug 08 2008, 04:09AM
Nice Job!
and good idea to use a vacuum filtration flask... any idea what the pressure inside of the tube is?
Hon1nbo, Fri Aug 08 2008, 04:09AM
Nice Job!
and good idea to use a vacuum filtration flask... any idea what the pressure inside of the tube is?
Re: Homebuilt Cathode Ray Tube
uzzors2k, Fri Aug 08 2008, 10:26AM
That's incredible! Connect some signal generators to the deflection coils and make some patterns for us. This tops my list of weekend projects.
uzzors2k, Fri Aug 08 2008, 10:26AM
That's incredible! Connect some signal generators to the deflection coils and make some patterns for us. This tops my list of weekend projects.
Re: Homebuilt Cathode Ray Tube
Myke, Fri Aug 08 2008, 05:47PM
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.
Myke, Fri Aug 08 2008, 05:47PM
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.
Re: Homebuilt Cathode Ray Tube
Hazmatt_(The Underdog), Fri Aug 08 2008, 07:39PM
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.
Hazmatt_(The Underdog), Fri Aug 08 2008, 07:39PM
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.
Re: Homebuilt Cathode Ray Tube
aonomus, Fri Aug 08 2008, 09:01PM
Wow, never would have thought of using a filter flask.....
How did you transfer the phosphor coating from fluorescent tube to flask?
aonomus, Fri Aug 08 2008, 09:01PM
Wow, never would have thought of using a filter flask.....
How did you transfer the phosphor coating from fluorescent tube to flask?
Re: Homebuilt Cathode Ray Tube
reign, Fri Aug 08 2008, 11:26PM
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.
reign, Fri Aug 08 2008, 11:26PM
aonomus wrote ...
Wow, never would have thought of using a filter flask.....
How did you transfer the phosphor coating from fluorescent tube to flask?
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.
Re: Homebuilt Cathode Ray Tube
Atomic Parts, Sat Aug 09 2008, 04:42AM
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
Atomic Parts, Sat Aug 09 2008, 04:42AM
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
Re: Homebuilt Cathode Ray Tube
aonomus, Sat Aug 09 2008, 05:15AM
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.
aonomus, Sat Aug 09 2008, 05:15AM
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.
Re: Homebuilt Cathode Ray Tube
Atomic Parts, Sun Aug 10 2008, 06:13PM
Here is a picture of the unit.
Atomic Parts, Sun Aug 10 2008, 06:13PM
Here is a picture of the unit.
Re: Homebuilt Cathode Ray Tube
Hazmatt_(The Underdog), Sun Aug 10 2008, 06:21PM
what kind of electrodes do you have sealed through the glass? and are you using Boro for the rear half of your tube?
I'm just wondering if you've sealed Kovar or Tungsten into Boro, or if you're using a softer glass for the gun component.
Hazmatt_(The Underdog), Sun Aug 10 2008, 06:21PM
what kind of electrodes do you have sealed through the glass? and are you using Boro for the rear half of your tube?
I'm just wondering if you've sealed Kovar or Tungsten into Boro, or if you're using a softer glass for the gun component.
Re: Homebuilt Cathode Ray Tube
Atomic Parts, Sun Aug 10 2008, 07:28PM
The cathode is aluminum and the anode is copper. The vacuum flask and the test tube (inner electron gun) are both boro. The gun housing is made from a softer glass I purchased from a kitchenware store. Its defininately not what you would call high quality. However, due to its 1/4" wall thickness its very suitable for low temperature vacuum use. The electrodes sealed into this gun assembly are indeed tungsten. From one electrode, I have spot welded a stainless steel tig line to the copper anode. I learned a lot from this design and am ready to upgrade.
As of now I have pretty much discarded the entire gun assembly exept for the flange. My new gun will be a bit longer with a biased focusing anode, smaller anode aperature, and all stainless construction.
Mark
Atomic Parts, Sun Aug 10 2008, 07:28PM
The cathode is aluminum and the anode is copper. The vacuum flask and the test tube (inner electron gun) are both boro. The gun housing is made from a softer glass I purchased from a kitchenware store. Its defininately not what you would call high quality. However, due to its 1/4" wall thickness its very suitable for low temperature vacuum use. The electrodes sealed into this gun assembly are indeed tungsten. From one electrode, I have spot welded a stainless steel tig line to the copper anode. I learned a lot from this design and am ready to upgrade.
As of now I have pretty much discarded the entire gun assembly exept for the flange. My new gun will be a bit longer with a biased focusing anode, smaller anode aperature, and all stainless construction.
Mark
Re: Homebuilt Cathode Ray Tube
teslacoolguy, Sun Aug 10 2008, 09:13PM
How did you coat the phosphor to the inside of the flask?
teslacoolguy, Sun Aug 10 2008, 09:13PM
How did you coat the phosphor to the inside of the flask?
Re: Homebuilt Cathode Ray Tube
Mads Barnkob, Sun Aug 10 2008, 09:39PM
Mads Barnkob, Sun Aug 10 2008, 09:39PM
teslacoolguy wrote ...
How did you coat the phosphor to the inside of the flask?
How did you coat the phosphor to the inside of the flask?
reign wrote ...
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.
aonomus wrote ...
Wow, never would have thought of using a filter flask.....
How did you transfer the phosphor coating from fluorescent tube to flask?
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.
Re: Homebuilt Cathode Ray Tube
FastMHz, Wed Sept 03 2008, 09:41PM
This is really neat, good job!
FastMHz, Wed Sept 03 2008, 09:41PM
This is really neat, good job!
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