New to the forum, and I have a CRT question - Page 1
Forum section: electronics / beginners

author: larrybl
author_rank: Regular Contributor
timestamp: August 16, 2014, 07:15:54 pm
content: I've been watching Dave's work for a while. I was bitten by the electronics bug way back when I was a kid and everything was tube based. After 21 years in the Military and the various jobs I have had I have progresses to be the current manager of a digital public safety communications system. Recently I came across a Sony "Super bright" video projector, and proceeded with a tear down. All was as I expected, basically three monochrome crt's but with a twist. I have never seen a liquid cooled crt before. I would like to know more on how they managed to get enough light from a crt to project on to a 4' screen without burning the phosphor out.Thanks for the forum!Larrybl

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 16, 2014, 07:20:07 pm
content: Didn't you answer your own question? Clearly you can't get that kind of brightness out of a CRT unless you have some extraordinary way of keeping the phosphor cool enough to not toast. Are you saying that the liquid is self-contained and not circulated (to cool it down with an external radiator)?

author: Yago
author_rank: Frequent Contributor
timestamp: August 16, 2014, 07:32:49 pm
content: Are you sure you have note misread "liquid coupled"?http://www.curtpalme.com/CRTPrimer_13.shtmIDK, just found that phrase googling.

author: Simon
author_rank: Unknown
timestamp: August 16, 2014, 07:44:38 pm
content: Quote from: Yago on August 16, 2014, 07:32:49 pmIt say's liquid coupled/cooled, it sounds like the liquid helps cool it but then that small amount of liquid will just heat up and without it being cooled it will just boil away

author: larrybl
author_rank: Regular Contributor
timestamp: August 16, 2014, 07:55:24 pm
content: Quote from: Yago on August 16, 2014, 07:32:49 pmThank you for the link. I think mine is older (1978 I think) than those displayed, It was working before I tore it apart. I have replaced it with a Sharp DLP projector, 5 lbs vs 70 lbs and a 100% better picture. I was just surprised at the liquid (Pink, blue-green, and clear). It seems the heat sink part is pressed on to the tube, but closer inspection it appears the fluid is touching the CRT, so removal of the heat sink may be impossible.Thanks for the replies.

author: Simon
author_rank: Unknown
timestamp: August 16, 2014, 08:04:01 pm
content: Well I can't see that the heatsink is in contact with the fluid and it's not much of a heat sink. You would need the liquid to be in contact with an aluminium surface so that it can extract heat and then your aluminium heat sink would need to be quite large to dissipate the heat or be forced air cooled by a fan.The use of a coloured liquid in colour image devices dates back to the early days of colour photography when each colour was "shot" separately with a liquid filter over the lens because it was easier to get colour consistency and quality of transparency with liquid than something solid

author: IanB
author_rank: Super Contributor
timestamp: August 16, 2014, 08:43:02 pm
content: Quote from: larrybl on August 16, 2014, 07:55:24 pmI suspect the liquids are fluorescent and the colors are cyan, magenta, yellow. The advantage of liquids may be that you won't get a single hot spot and burn in since the liquid can continually circulate and mix. Any single bit of the liquid that is glowing brightly will heat up and move away by convection to be replaced by cooler liquid from nearby.

author: larrybl
author_rank: Regular Contributor
timestamp: August 16, 2014, 10:07:42 pm
content: Quote from: IanB on August 16, 2014, 08:43:02 pmInteresting, so the fluid (yes those are the colors) may be fluorescent and assist in increasing the brightness, hence the label Sony Super Bright. If I could get one of those filters off I would like to experiment with it.

author: larrybl
author_rank: Regular Contributor
timestamp: August 16, 2014, 10:12:42 pm
content: The "Yellow" CRT shows some burn in, I didn't notice this in the other two. There is also two small set screws that I removed, but the cover isn't budging.

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 16, 2014, 10:33:46 pm
content: CYM (cyan, yellow, magenta) are SUBTRACTIVE primary colors. You cannot create the spectrum with CYM light. CYM is used for reflective things like full-color printing on paper.RGB (red, green, blue) are ADDITIVE primary colors. RGB is used to create the full spectrum of colors with light.It seems unlikely that the fluid would be involved in generating color (as with flourescence) as it has zero resolution.

author: IanB
author_rank: Super Contributor
timestamp: August 16, 2014, 10:54:54 pm
content: Quote from: Richard Crowley on August 16, 2014, 10:33:46 pmIndeed.QuoteTrue enough.QuoteAnd yet the liquids do appear to be cyan, magenta and yellow. This is surely not a coincidence. I feel rather certain that the liquids are in some way involved with the color generation.For instance, suppose the cyan liquid absorbs or reflects green and blue light and transmits red light? Similarly with the magenta liquid (green) and yellow liquid (blue). Then a sharp image could be projected onto the phosphor behind the filter giving the required contrast and the filter could help with the purity of the color?

author: miguelvp
author_rank: Super Contributor
timestamp: August 16, 2014, 10:59:45 pm
content: Good point IanB. Would that mean those CRT's project pure white?Therefore the filters are used to subtract the unwanted colors?

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 16, 2014, 11:05:31 pm
content: It would be interesting to see what color the phosphors are. You could do a quick-n-dirty test by exposing them to strong light (like sunlight) and then very quickly, observe them in the dark to see what color they fluoresce. Indeed the fluid may serve as an optical filter. But they don't seem very "sharp". The color seems rather "pastel" indicating it isn't all that effective. Or they may have decayed into those colors over years of high-intensity exposure.

author: IanB
author_rank: Super Contributor
timestamp: August 16, 2014, 11:10:28 pm
content: Optical filters don't need to be sharp. Only the image needs to be sharp, and only at the focal plane of the lens (at the CRT phosphor).

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 16, 2014, 11:14:35 pm
content: I meant "sharp" in terms of "frequency response", i.e. the shape of the cutoff above and below the color of interest.

author: larrybl
author_rank: Regular Contributor
timestamp: August 16, 2014, 11:36:21 pm
content: The phosphors all appear white, (I bet with a green trace) I could use a bright light this evening when it is dark to check. It looks like the fluid is mainly for color rather than cooling. I found a reference to a post dated 6/19/2002 at avsforum on how to repair a SD-187 that has leaked, and caused a "fungus" type of appearance in the display. From what I gather, the fluid can be drained, and the front shield removed, but I would have no way to experiment with it.--------------------------------------------------------------------------------------------------Guys -- these SD187 tubes, at least in sony units, are easy to de-fungus. I dont imagine it to be different in any PJ that uses this tube other than the physical removal of the tube from the PJ. It does take some prep and might span several days, but total time should only be about 1-2 hours per tube once removed.The first set I ever did was based off threads here. Until reading the threads I just swapped tubes. Now I wish I had all those tubes I tossed. The following is based in part on those threads and from my personal experience. If this is your first go round, do one tube at a time.______________First round up a razor knife, some black RTV silicone, fish air line tubing, a syringe if available, a Pyrex dish (LARGE), some dish detergent, a green scrubber thingy (NOT the harsh kind; get the soft one so you cant scratch glass!), one bic pen (the cheap Bic Stick type you can pull the ink insert out of) and finally, some coffee filters. I might be leaving a few things out...Remove the bic pen ink tube. Carefully cut the ink tube (not the part you hold onto) so that you have about 3/4 inch of clear hard tubing without ink. Toss the pen carcass. From here on out this 3/4 inch X 1/8" (aprox) tube will be called the bic pen.Attach 1 foot of air-tube to the bic pen tube. Silicone the seam of the tubing/pen and allow to dry overnight. The air tubing (end without the bic pen ) should be able to slip on/off the syringe (obviously without a needle) as-is. A "turkey baster" or similar device will probably work in place of a syringe. Congratulations. You just made the easiest adapter possible to (reasonably) fit these SD-130 and SD-187 tubes, and it will probably work for others.Remove tubes from the PJ. I unsolder the wires from the magnetics so I do not need to remove the magnetics from the tube. You can also slide the magnetics off, but I think there is more risk in doing so. Make yourself a drawing so you dont forget which wires go where.Get a deep pyrex type dish. Remove the two screws (fill holes) from the top of the tube. Make SURE you save the little gasket, else you will be siliconing the screws in place. Pay attention to how tight the screws are. Insert a long thin sewing needle into each each hole where the two screws were until you see the needle in the face of the tube. Remove the needle. Do this several times to clear the fill port so you can easily get the fluid in and out. Set your tube into the pyrex dish. The fill screws should still be removed. Tube may leak fluid- its OKAY! THATS WHAT THE DISH IS THERE FOR!Grab your fish-air-bic-pen-silicone-contraption-hose adapter. Turn the tube sideways in the dish. Place the bic pen end onto one of the screw holes (which ever hole is higher up) and GENTLY blow air into the tube. Forcing air into the tube will build up pressure between the glass front and tube face, resulting in the fluid being rapidly ejected from the fill hole on the bottom. Tilt the tube as needed while blowing into the adapter to remove all fluid.SAVE THE FLUID unless you are going to use new fluid. If you are going to use new fluid, skip down to the ________ line.Now this fluid - argh what a slimy concoction it is... Cut a coffee filter so you have just a small portion of the cone. Paper clip the filter to the side of a glass, preferably something like a mason jar with a lid. I would not reuse the glass for anything else; dispose of it when you are done...Take the adapter you made, using the syringe suck up some fluid from the Pyrex dish and place it carefully into the filter so that your cup catches the filtered fluid. It might take a LONG time for the fluid to pass through the filter. Don't rush it! Be careful- if *ANY* fluid escapes the filter and ends up into the cup unfiltered START OVER. Don't take shortcuts if you are filtering and re-using the fluid unless you are having a lot of fun so far. By the time you finish the few ounces of fluid, I think you will agree you don't want to do this again unless you are making $$.Now that your fluid is filtered - and I am sure visibly clearer- put the cap on it (now you see why I said mason jar) and set aside. We will come back to it later)___________ Skip down to hear if you are using new fluid_____________CAREFUL! Insert a razor knife (The long thin kind) into tube between glass front and tube. Work razor back and forth carefully until the blade is visible inside the tube- then cut all the way around the face of the tube. You will reach a lip on the aluminum frame where the knife can not pass. Pull the glass black and cut the silicone in that portion until you have the glass off. Be careful not to gouge the aluminum or scratch the glass. If you made it this far, and the glass is in one piece, you WILL get the job done! Have faith!Scrub the tube face and glass cover getting it reasonably clean, then dry it with whatever is soft and lint free.Now take your razor knife and remove as much silicone from the glass as possible. Do the same on the tube frame, again being careful not to gouge the frame.Clean the fill holes out again with a needle, then with water. I place tubes into a large freezer bag and the tape the bag to the back of the tube to keep the magnetics dry. Use a sink sprayer to spray the fill holes and frame with as much force as you are comfortable using to make sure the holes are clean. Its important to remove every bit of that silicone along with the dirt from the fill holes. Remember- miss one piece and you will be starting all over.Now that you have the silicone gone and the fill holes are clean, scrub the glass front (both sides) and tube face and allow to dry. Repeat several times. I PROMISE no matter how careful you are you will NOT (no way, no shape, no how!) get the tube face and glass front free from all that crud the first go round. Remember my warning--- miss one piece and you will be starting all over.Make sure everything has been dried. I use a hair dryer so as to not leave lint on the glass.Okay- Now we are ready for the serious stuff.With someones help- apply a 1/4 inch bead evenly, IT MUST BE EVEN, all the way around the metal frame where the OEM silicone was.Important hint: If you get ANY silicone where it doesn't belong --such as a big glob on the tube face --- STOP, let the silicone dry, then remove it and start over. If you try to remove the silicone while it is wet you will make 100 times the mess.Have someone hold the tube face up for you. Carefully center the glass front. PRESS the glass into place on the frame. Make sure you can see the silicone touching the glass 100% along your bead. Its okay if some of the goo comes from the edge of the tube, and a slight bit inside the face wont matter much either, as long as it doesnt extend to where your raster will be. Again, make sure you can see the silicone touching the glass 100% along your bead. It wont hurt to press the glass into place again, but dont try to slide it around or you will mess things up.Sit down and hold your tube ( dont even go there!) face up for about 15 minutes. This will allow the silicone to "skin" and hopefully the glass will not slide all around on the next step.Dont slide the face around to see if the silicone has skimmed! It will slide, and you will have a mess.Place a soft dishcloth on the tube face. Take an old plate and place onto the cloth, again being carefull not to slide things around. Holding the plate in place to keep the glass front on the tube face, carefully set the tube FACE DOWN on something level. If you have goofed and slid the front glass around you will probably end up starting over. Placing the tube face down at this point will allow the weight of the tube to be applied to the face/silicone while the goo cures. Allow the tube to dry face down for at least 24 hours, preferably a couple of days. Dont even think of picking it up before 24 hours has passed. Its better to allow a couple of days, if possible, for the silicone to completely cure.Now that some time has passed, pick your tube up and check your silicone job. If you are satisfied it will not leak and that no silicone extends into any part of the phosphor used for the raster, you are ready to proceed.Hint: Too much silicone around the edges can be carefully trimmed off. Too much inside or not enough? Sorry to say this, but you will need to start over.Wow. Take a deep breath. Okay. the hard parts are over, and Im glad because Im getting tired of typing.Set the cleaned/reassembled tube, into the (wash it first) pyrex dish. Grab your adapter and install in onto your syringe. Dip in your filtered fluid and draw up as much as practical. Insert bic pen of adapter as tight as possible over fill hole ans slowly release the fluid into the tube. If you are holding things properly and both fill holes are open you will spill little to no fluid. Have at it until all filtered fluid is in the tube. You will likely find you have about 1/8" or so of less fluid in the tube then when you started because of what the filter absorbed. Some use distilled water, some glycol, but nonetheless top the tube off with whatever you are comfortable with until you have a small bubble about 1 inch wide remaining. Clean the two screws and put back into the fill holes. Dont forget the gasket. If you lost the gasket or it broke, tighten the screws a few turns, then apply a drop of RTV silicone to the underside of the screw head. Tighten "finger tight" and allow to dry. Now tilt the tube various direction to make sure there are no leaks.IMPORTANT- DONT SHAKE THE TUBE to try to get the micro-bubbles out! You might destroy the tube. the micro bubbles will work out on their own over a few days time once the tube is back in the PJ.Re-install the tube into the PJ. Needless to say you probably need to do a full physical setup, calibration, registration, etc...Smile- You only have two more tubes to go! :-)Enjoy! Hope this helps someone. Maybe Ill take pics of the next one I do.--Kieth

author: Yago
author_rank: Frequent Contributor
timestamp: August 16, 2014, 11:45:25 pm
content: I did read a patent somewhere that it also served to shield xrays (to mixed success).

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 16, 2014, 11:53:35 pm
content: It appears that the cooling/coupling fluid is supposed to be crystal clear, and develops those colors after long exposure. They sell replacement (clear) fluid and people report greatly increasing the image quality of their projectors after replacing the discolored fluid. It appears that the green and blue colors promote growth of algae and they are particularly susceptible to this kind of problem. But the red color apparently kills algae. Be very careful with that fluid if you drain them.

author: larrybl
author_rank: Regular Contributor
timestamp: August 17, 2014, 12:00:41 am
content: Thanks all, I think I have the answer I was looking for, and discovered more than I expected on the subject. Seeing that these are well used up, they will be disposed of. Any recommendations on disposal? Normally the old CRT TV's just get tossed in the dump, That is what I plan for these.

author: SeanB
author_rank: Super Contributor
timestamp: August 17, 2014, 05:57:07 am
content: The cooling is very effective, it just has to handle the 30W or so of heat produced at the front of the CRT from the beam. The front glass is leaded and transfers the heat through to the fluid, which then can circulate around to allow the heat to evenly heat the case and then the forced air cooling will remove it. Those CRT's will burn out in around a half hour with no fluid, and will darken a lot from the bottom of the screen as the fluid leaks out ( as the image is inverted by the lens so the top of the CRT in the projector is actually shown on the bottom of the screen) leaving a burn on the CRT when you take it out.Disposing should be done to a glass recycling place that takes CRT's, but otherwise drop in any Ewaste recycling bin.