LD#13: The care and feeding of laser videodiscs Version: 13 Jul 92 Part 1 Revised: 01 Mar 92 Part 2 Revised: 28 Jul 90 Part 3 Revised: 13 Jul 92 Part 1 of 3: How to avoid needing parts 2 and 3 The following narrative of LD care is in life-cycle order. The part 1 scenario presumes that you have just bought a disc. If it is a factory-new disc, or still in print, and can be exchanged, I do NOT recommend the part 2/3 repair procedures. Exchange the disc. Disclaimer: These are the practices that I follow. The industry at large doesn't seem to have any. These practices are not warranted in any way whatever, and this series of articles was partially intended to provoke discussion and counter-suggestions. Prerequisite: you need to know that the video data for side "X" is on the opposite side of the platter from the label for side "X". Also, LDs play from the inside to the outside. Myth: LDs are indestructable. You can handle them anyway you like. The laser can read right through fingerprints, smudges and scratches. You may even have seen a [scam] demo of a salesdroid *writing* on an LD and then playing it with no apparent damage (and also without turning it over, which avoids testing the damaged side). The myth is false. Apart from the digital sound (if present), LD error correction consists solely of a "drop-out compensator", that can "correct" a lost scan line by re-using the previous one. The laser has a limited tolerance for optical obstructions. If you can see damage (or defects) in the acrylic, there is a strong possibility that you will see video noise (or worse) on the screen. You may even hear it on the analog channels. LDs are more robust than LPs, but for longest life, and most satisfactory viewing, treat them as you would an audiophile LP. LDs are not as robust as CDs. _ _ _ _ _ _ _ _ _ 0. If you live some distance from your LD store, as I do, you might consider opening all purchases and checking them on a store player before heading home. I do this routinely with used discs. If buying a used, remaindered, ex-rental or otherwise "remarketed" disc, check contents when you leave the store. Compare the platter labels (and side count) to the jacket art, and make sure that some sleazy customer has not, for example, switched old all-CLV analog pan&scan platters for the CLV/CAV digital widescreen ones you just paid for. [This scam is rare.] Go home. Make sure you have an adequate supply of inner and outer sleeves, and a clean dust-free work surface. Wash your hands, too. 1. Remove the shrink wrap. Over-tight wrap is the leading cause of "dish" or "cone" warp, where the disc describes a shallow cone when placed on a flat surface. Do not store LDs in their original taut wrap. If the wrap is the traditional taut variety, carefully slice it along an opening in the underlying slip case or box. Peel it off, taking care to avoid ripping any stickers affixed to the wrap. Save the wrap for the moment. If the wrap is the loose slightly oversize variety common on Japanese imports and IMAGE/Kuraray production, consider using it as the outer storage sleeve. Cut carefully and evenly along the top, removing as little plastic as possible. 2. Inspect and play (sample) the disc. Before investing any more work, make sure there are no defects. Remove any stray dust particles or hair with a soft lint-free cloth. I don't recommend compressed or canned air sources, as these emit very cold air which can thermally stress the disc. Also, some can emit liquid propellant, with uncertain results for your media. Inspect the disc surfaces for gross dangerous defects, like severe warp, side-to-side mis-alignment and cracks (linear and starburst). If any - DO NOT PLAY. (Manufacturing and shipping cracks occur in about 1 of 400 titles.) Sample the disc(s). Turn on "DISPLAY" to show the chapter number and time/frame. Play the sides in order, paying some attention to the program content and chapter. (I have seen two mis-labeled sides so far.) If it is extensively chapter-marked, skip thru by chapter. If a generic CLV, play the start of each side, and seek to 11:11, 22:22, ... 66:66 etc. If CAV, play start plus frame 11111, 22222, ... 55555. When one of the seeks takes you to the end of a side (and 66:66 or 55555 surely will), back up and watch the end of the side. Problems are usually the most prominent there. Find a problem? I have a separate article available. #17, "LD: What is a defect?" 3. Transfer stickers. If the wrap bears any distributor sticker, carefully peel it off and apply it to some blank area on the back of the cardboard slipcase or box. If an LDC or Pioneer sticker, make sure to avoid obscuring the LDC, LDCA, PVI or LDV emboss (if any) on the lower left corner of the back cover. Transfer the price tag to the inner sleeve (to be used). If the disc was obtained in trade or replacement, you may not have a receipt for it, and the preserved price tag may be your only record of the disc's value. Discard the shrink wrap. 4. Upgrade the inner sleeve(s), also known as "liners". Unless the disc is a 3M, PDO, recent Technidisc or a Voyager Press / Criterion Collection, the inner sleeve(s) will be the flacid U-shaped unreinforced translucent plastic variety. These provide inadequate protection. They collapse, leaving exposed arcylic rubbing against the cardboard jacket. They often won't go back into the jacket properly and encourage careless handling of the media, not to mention the risk of embossing sleeve creases into the disc in storage. Use poly-lined paper-reinforced rectangular sleeves, with center holes that allow reading the labels on both sides. I order them from Starship Audio-Video, but Radio Shack catalog# 42-132 sleeves will do. Reinforced sleeves are particularly important for multi-platter sets that are in single-slot jackets or boxed. See also step #3. If the disc already had a quality sleeve, but was used or a rental, you might want to replace the sleeve anyway. It may be coated with food oils and salts left by popcorn-eating renters. 5. Disc insertion. Always handle the disc by the outer edge and/or inner (hole) edge. Never touch the data surfaces. Handle the disc with clean, dry hands. Even if potato-chip/popcorn fingers don't touch the data surface, they will touch the inner surfaces of the sleeve, and the sleeve will transfer the oils and abrasive salt crystals to the disc. Insert the sleeve into the jacket with the sleeve opening UP, not facing out the jacket opening. Don't give the disc a chance to roll out onto the ground and crack. 6. Outer sleeve. For ordinary use, I store my discs (in their jackets) in re-sealable polypropylene sleeves or ordinary polyethylene outer sleeves, available at most used LP stores (and LD mail order houses). For transport and loaning, I use a small number of LD-size PVC ziplock bags, obtained from a regional LD sales and rental store. PVC sleeves are on the market under several brand names, such as "LaserShield". I do not recommend the use of PVC (polyvinylchloride) for long-term storage of anything, including LDs. PVC outgasses vinyl chloride over time, which can attack metals and other plastics. The purpose of the poly sleeves is to prevent damage to the jacket artwork and minimize air circulation if you live in a humid climate. In a normal storage cabinet, the insertion resistance is high enough that unprotected, the jacket art and text will eventually be scuffed away. The zip sleeves prevent the disc from sliding out of the sleeve during transport. Holding the jacket in the normal horizontal position insert it in the outer sleeve with the sleeve opening up. As with the inner sleeve, the openings are at right angles to each other, preventing the disc/inner sleeve from sliding out accidentally. 7. Database? If you keep a log of your purchases, or a list of your collection, now is the easiest time to update your records. At a minimum, I suggest: * Write the title and catalog number of each disc on the back of the store receipt, invoice or packing slip. If the retailer name and date do not appear on the slip, write them as well. * Write the platter serial numbers (if any) under each title. Should your collection ever get stolen, these may help in recovery. There may be several sets of numbers stamped, embossed, engraved or mastered into the disc data surface. (I have a separate article available on LD mint marks.) Drop the receipt in a large ziplock baggie (with all the other slips), and store it separately from your collection. 8. Store the disc. Attributes of a reasonable storage cabinet are: * Stable temperature - in particular, never let sunlight fall on the cabinet or the discs. If possible, 10 degrees C is recommended. Acrylic plastic begins relaxing at 60 degrees C, and glasses at 90C. * Low humidity (30% RH) - acrylic plastic is hyrgoscopic, and tends to warp when wet. Water vapor can infiltrate, leading to trouble down the road, particularly if your air is polluted. If you live in a humid climate, and don't have a de-humidified room, at least keep the humidity stable. * Store the discs vertically (not horizontally), and pressing lightly against each other. Make sure that the surface or bookend at each end of the stack presses evenly against the entire face of the end LDs, otherwise, warps are likely. Store 8-inch and 12-inch discs separately. * Save cardboard fillers from LD mail orders. They make great cabinet spacer material to prevent disc stacks from leaning. Leaning can result in warp. * Play (or at least sample) the disc once per year. In addition to catching any decay early, this will probably reorient the disc in the sleeve, preventing the plastic flow of arcylic that can occur over geological time. Keep the discs in storage when not in use. Keep them away from pets, sunlight, radiators, hot/warm audio/video equipment surfaces, teenage mutant ninja turtles and other destructive forces. Don't leave a disc in the player overnight: running, paused or stopped. 9. Playing the disc. Observe the handling precautions listed earlier. If you have an early tray-loading player, where the tray is not fully exposed when open, carefully navigate the disc into the player, avoiding any contact with player caseparts. If you find that you frequently bump the disc into some player part, apply a protective covering to the part. The soft felt-like "loop" side of self-adhesive Velcro(TM) strips may provide the protection you need. If the player has disc support pads in the data region of the disc (and many do), lower the disc vertically onto the pads without sliding or spinning it. Also, periodically inspect the pads for the presence of abrasive debris; vacuum up any found. If stopping play and ejecting the tray are two separate operations on your player, always wait for the disc to completely stop spinning before ejecting. I have seen CDs destroyed by players that dropped the CD, still spinning, onto in-data-area supports. Always remove the disc from the player, return it to its slipcase and store it immediately. The disc is warm and dry after play, and will most benefit from being in a proper storage configuration. Under no circumstances leave a disc in the player for any length of time after play, as plastic flow may cause it to sag and develop warp. END OF PART 1 OF 3 --------------------------------------------------------- re: The care and feeding of laser videodiscs Revised: 28 Jul 90 Part 2 of 3: Correcting warps. re: > .. laserdisc, only it's warped to the extent that my player produces > video noise when the head is in the outer sections of the disc. I > would like to fix the warp myself rather than returning it. What's > the fix for a warped disc, 0. Read these instructions and have all materials handy. 1. Obtain two sheets of optically flat glass, at least 12x12-inches. 1/4-inch plate is ideal, but ordinary window glass will do. Clean them and place them in an ordinary oven at the lowest possible setting. 2. Select the most wrinkle-free LD inner sleeve from your collection. A 3M-style lined paper type with center hole is ideal. Place the sleeve in a warm place, like in the sun. 3. Using a soft, slightly damp, lint-free cloth, wipe all debris from the disc. Wipe radially, from the inside out. 4. Warm the disc up to about 100 degrees F. Playing it for two hours will accomplish this, but only if, a: the disc is still flat enough to play without striking player parts and, b: it will actually play, rather than being rejected by the player. If the disc cannot be played for two hours, fill a sink full of water at 100F. Insert the disc in a jumbo size zip-lock bag and insert it in the water up to, but not beyond, the zip closure. Keep it there for five minutes, dipping up and down to circulate the water. When removing it from the bag, take care to keep it dry. 5. Quickly insert the disc in the warm wrinkle-free sleeve and place the sleeve/disc between the warm sheets of glass. Place the sandwich on a towel on a firm flat surface. Stack a pile of books on top (about 10 pounds). Make sure the bottom book is close to 12x12 itself. Place the stack away from sources of heat and leave it that way for two days. 6. If that fails, replace the book stack with a large pan or pot full of water at 100F. Select a vessel with a flat bottom. If no joy, work up five degrees at a time to higher temperatures, but don't exceed 140F. > ...and is the fix permanent, or will it slowly return to being warped? If the disc is a 3M (Imation) casting, made by the non-thermal "2P" photo-polymer process, it probably will not re-warp. For all other brands... It depends on why it warped in the first place. If it warped due to "trauma", such as over-tight shrink-wrap or exposure to bending stress under high temperature, it may remain flat. On the other hand, if it warped due to release of inherent manufacturing stresses, then it may very well re-warp when warmed up by your player. If you have an old gas-tube laser player, the disc will experience more heat than with a contemporary solid-state laser player, and will be more likely to re-warp. If the disc has "cone" warp, and you have a two-sided player, always playing it in the "cone edge up" configuration may prevent re-warp. Any tendency to sag should cause the disc to resume being flat. Disclaimer: Although I have a couple of discs with "cone" warp, I haven't needed or tried the above techniques personally. These suggestions are supplied without warranty of any kind. Your disc will probably melt and catch fire. I would consult other sources before trying anything. Batteries not included. Your mileage may vary. Simulated TV picture. END OF PART 2 OF 3 --------------------------------------------------------- re: The care and feeding of laser videodiscs Revised: 13 Dec 91 Part 3 of 3: OK, so somebody goofed, and now you have a damaged disc... Step zero: Is the problem in your player? Verify the media problem on another player. If the problem disappears on another machine, yours may need cleaning, adjustment or repair. I don't recommend attempting to clean the player yourself, and I especially don't recommend using "laser lens cleaning" CDs. There have been reports of player destruction from these furry platters. Player adjustment and repair requires a service manual, a $120 test disc (Pioneer GGV-141), an oscilloscope, other test equipment and training. First - do you need to do anything, and if so, where? Remembering the prerequisites from the base article, try to estimate where the media problem would be in the video program. For fingerprints, mild scuffs and scratches (only), play the disc near that region. If the problem is not evident on the screen, think twice about doing anything about it. Do not routinely wash discs until you have some experience with the process from discs that really need it. If you have any old hopeless LDs (e.g. unplayable DiscoVisions), you might want to practice on them. Your dealer may be able to supply some worthless defective discs. Tools needed (but read the instructions before investing): - Large sink with faucet and water stream adjustable to constant lukewarm. - Mild non-abrasive liquid dish soap (e.g. Joy). - Small soft sponge. - Small clean non-abrasive rags. - 12x24-inch (or larger) soft, clean, reasonably lint-free towel. - Peanut oil. - Isopropyl alcohol. - LD player. - Prist Acrylic, Plastic and Glass Cleaner (spray) PPG L555-A1-387A - Prist Plastic Polish (liquid, FedSpec PP-560B) PPG L555B-1A-1187A - Micro-mesh Scratch Removal and Restoration Kit KR-70 - Wet-dry abrasive sheets in grits #600, 1200 and 1500 (local hardware). - A paste wax, such as Johnson's The Prist and Micro-mesh products, intended for acrylic aircraft canopies, may be available from Sporty's Pilot Shop (Ohio, 800-543-8633). I have not used or inspected any of the LD cleaning machines advertised from time to time. I therefore cannot recommend any of them, and several make me suspicious just from their descriptions. There is also a "CD/Laser Disc Repair & Protection System" marketed by "BUNDEE International". It contains three small plastic bottles of fluids containing unidentified "petroleum distillates", plus 4 polishing cloths. It had no apparent effect on a damaged LD I attempted to repair with it. * Locating the problem: If the defect/damage is not visually obvious, you will need to find it. Note the time (in minutes) or the CAV frame number at which the problem occurs. If CAV, also try to figure out if the program was transferred using 3/2 pulldown from film, or 2/2 pulldown from video (or incorrectly from film). If there is field-motion during still frames, it is 2/2. If there are more than 43,200 frames on the side, it has at least some 2/2 material. I have a separate article available on 3/2 pulldown. You can also note the difference in frame counts after running for 10 seconds. If 300, then it is 2/2. If 240, then it is 3/2. 1. The data surface for side "A" is on the opposite side from label "A". 2. LDs play from the inside out, starting at a radius of about 2.1 inches. (Radius is measured from the center of the hole.) 3. Rotation of the data surface with respect to the laser is counter- clockwise. This is only useful information on CAV disks. A single- point source of bright light (e.g. the sun) is useful for visually inspecting CAV disks. 4a. On NTSC CAV, the approximate radius position (R: in inches) of the problem is given by: R = 2.1 + (0.12 * TIME) {if your player has a CAV time mode} R = 2.1 + (FRAME / 12000) {for 3/2 pulldown from 24 fps film} R = 2.1 + (FRAME / 15000) {for 2/2 pulldown from video} The wide radial arms on the disc are the video "vertical interval" (VI). If the problem exhibits itself near the top of the screen, it will be just to the left of one of the VI bands. If near the bottom, then just to right, etc. Each of the small radial arms in between the VIs is a single horizontal scan line. You can see that a pinhead size problem can wipe out most of a video scan line in several frames. 4b. On NTSC CLV, the approximate radius position (R: in inches) of the problem at a known TIME in minutes is given by: R = SQRT ( ( TIME + 9.421 ) / 2.136) ) Since the vertical intervals are not radially aligned on CLV, knowing the screen position of the problem is generally not helpful. Indeed, if the problem affects several frames, it usually scrolls up or down the screen precisely because the frames aren't aligned on CLV. * Smudges, grease, fingerprints and stray platter glue: The first three are common on rental discs, and some used discs. Stray glue is common on 3M discs. ! Do not use any cleaners containing acids, ammonia, or strong petroleum solvents other than those listed here. - For 3M glue, first try water, then isopropyl alcohol, and peanut oil as a last resort. - If any of the smudges are price-sticker type adhesive, pour a 1/4 teaspoon of peanut oil on a small rag, and wipe the affected area. Let it sit for 30 seconds or so, then wipe it off with a dry portion of the rag. Always rub (lightly) and wipe radially. (from center to edge, as if along a bicycle spoke, and not circumferentially along the pit track). Remove residual oil with isopropyl alcohol. - If you are moving debris around that does not want to come off on your rag, it is safer to leave the debris at the outer edge of the disc. - If the smudge is unidentifiable, use a small rag again and try either isopropyl alcohol and/or Prist cleaner spray. Spray the Prist on the rag, not the disc. - Lay the towel out nearby, completely flat. - Soak the sponge with lukewarm water. Infuse with 1/2 teaspoon of soap. Squeeze out enough moisture that the sponge is not dripping. - Start the mild stream of water, typically from a faucet. Adjust to between 70 and 90 degrees F. - Wash, rinse and dry your hands. - With a very dry hand, hold the LD by the center hole at an angle so that the water stream runs away from the disc label. Try to keep the paper disc label dry at all times. Definitely keep all water and soap away from the center hole at all times. - Rinse the affected side once, rotating the disc around your dry hand. Rotate slowly so that the water most runs off, and doesn't run back toward the label as the wet spot rotates through 180 degrees, where the slope is back toward the label. - Wash the disc with the soapy sponge, still holding the disc at an angle. Wipe gently and radially (toward and away from the center, not along the pit track). Rinse as before. Inspect and rewash any particular problem areas. Do not wash the outer edge. - Rinse/wash/rinse the other side of the platter if conditions indicate. - Lay the disc on one half of the towel. Fold over the other half and gently tamp dry. Do not rub. - When all visible moisture is gone, play the disc for at least 20 minutes to force out any moisture that has infiltrated at the outer edge, and to completely dry the surface. The polymethyl methacrylate (PMMA) used to make LDs is hygroscopic (absorbs water), and you do not want any water to migrate and reach the data layer. * Scuffs: Any translucent or cloudy area remaining after the above treatment is apt to have micro-scratches. But try the above treatment first. - Lay the disc on the towel for support. - Use an acrylic liquid cleaner (e.g Prist). Follow the polishing directions, except rub and wipe radially. - Caution: Do not rub for very long in one spot. You want to avoid generating any significant amount of heat. The temperature differential created could mechanically stress, distort or damage the thin data metallization layer. - Rinse, tamp and spin-dry as above. * Scratches: I have used this technique to remove a circumferential scuff mark that had rendered a CAV disc unplayable for several hundred frames. - Try the scuff treatment first, then... - Use the Micro-mesh kit. Follow its directions, which will tell you to vary the direction of rubbing/polishing. With each grit, always begin rubbing/polishing circumfrentially, and end radially. Make each pass (with a shift to a finer grit) cover a slightly larger area, so as to polish out scratches left by the prior (coarser) grit. - Caution: As above, do not heat up the spot being polished. - Rinse, tamp and spin-dry as above. Wax and buff (gently & radially). * Gouges: Follow the scratch instructions, but start with #600, then 1200, then 1500 grits. * Cracks: Due to the risk of self-disassembly, player destruction and personal injury, I can't recommend that you make any attempt to repair a cracked disc. If the disc is broken (in pieces), forget it. The chances of getting the pit tracks properly re-aligned are about zero. "But please, Doctor Disc, this is only cracked and the last copy extant of this antique DiscoVision title." Well, OK. Now I haven't tried this, but this is how I would procede: Obtain a solvent-based adhesive intended for acrylic (or acrylate) plastic. "Weld-On" #4 and/or #16 cement has been suggested to me, available wherever Plexiglass or Acrylite are sold. Note that most hobbyist model glue is intended for styrene plastic, not acrylic. Ideally such a glue would consist of acrylic dissolved in the solvent/carrier. CAUTION: Work in a VERY well-ventilated area. Weld-On #4 contains Methylene Chloride and Trichloroethylene and Acrylic Monomer. Weld-On #16 contains Methylene Chloride, and Methyl Ethyl Ketone. These are dangerous and highly flammable chemicals. NOTE: These chemicals may have a completely different (or no) effect on CDs, which are made of Polycarbonate and not Acrylic. I cannot recommened cyanoacrylate ("super glue"). Although a swell adhesive, it is brittle when set. What you want to accomplish is to dissolve the abutting surfaces of the crack, reforming a homogenous surface. I'm not entirely certain that this is possible. (On acrylic aircraft canopies, the usual practice for crack repair is merely to drill a hole at the tip of the crack to prevent further propagation.) - A glue syringe will make the application job much easier. Available at most hobby shops. - Get an old top-loading LD player for testing the repaired disc. Do not risk large chunks of flying plastic making it impossible to open your current tray-loader. - Mix up a custom solution of glue/solvent. You want it thin enough to penetrate the LD crack by capillary action, but thick enough to leave a very small raised "bead" along the crack. You might try mixing some Weld-On #4 and #16. - Place a drop of the selected glue on a disposable polyethylene surface, like a sandwich bag. Note how long it takes to cure (harden) and how much it shrinks in so doing. You might separately try accelerated curing of other samples, e.g. in the sun. - Slightly bend the disc away from the crack, to open the crack. - Apply the glue mix to the crack. Wipe off the excess (from center to edge), then unbend the disc, causing some glue to be squeezed up out of the crack. Let this "bead" remain. It will shrink, and perhaps disappear, as the solvents evaporate. - Cure. Do not heat the disc above 120 degrees F. Using any kind of oven with volatile solvents is probably unwise. - However long the test drops took to cure, wait twice as long. - Using the "gouge" instructions, polish the bead (if any) flat. Polish the general area of the crack. - Test the disc in an "expendable" LD player. Press "PLAY" on the remote while standing in a concrete bunker down the street. Copyright 1990, 1991, 1992 Robert J. Niland All Rights Reserved Permission is granted for automatic redistribution of this article, via electronic, magnetic and optical media, in an unedited form, through any Usenet newsgroup where the article is posted by the author, through the Internet VIDEOTECH Digest and the Bitnet VIDTEK-L Listserv mailing list. Permission is granted for each Usenet reader, each VIDEOTECH or VIDTEK-L subscriber and each person who received this article from an ftp site authorized by the author or via electronic mail from the author, to retain one electronic copy and to make hardcopy reproductions of this edition of this article for personal non-commercial use, provided that no material changes are made to the article or this copyright statement. All other copying, storage, reproduction or redistribution of this article, in any form, is prohibited without the express written consent of the author, Robert J. Niland. Regards, PO Box 248 Bob Niland Enterprise mailto:name@isp-name.domain Kansas which, due to spam, is: 67441-0248 USA rjn AT access DASH one DOT com Unless otherwise specifically stated expressing personal opinions and NOT speaking for any employer, client or Internet Service Provider.