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For general viewing, subdued lighting but not total darkness is probably best. However, for most dramatic impact, a darkened environment may be preferred. Make the following adjustments under the expected viewing conditions. Tune to a strong channel or play a good quality tape. Turn the brightness, contrast, and color controls all the way down. Center the tint control (NTSC, may not be present on PAL sets). Increase the brightness until a raster is just visible in the darkest (shadow) areas of the picture. Increase the contrast until the desired intensity of highlights is obtained. Since brightness and contrast are not always independent, go back and forth until you get the best picture. Initially adjust the color control for pastel shades rather than highly saturated color. Set the tint control for best flesh tones. Then, increase the color control to obtain the desired degree of color saturation.
All of the service adjustments are accomplished either using controls inside the set (mostly pots on the mainboard and CRT neck boards), or in most newer TVs, mostly via a service menu accessed from the remote or by using a manufacturer specific computer interface. * A Web site with some information on the general objectives of video and color setup procedures for both direct view and projection TVs is: - http://www.Tru-line.com/ (Tru-line Video Technologies) * Where actual pots are present, they may be labeled on the circuit boards or identified by a sticker on the TV's cover. Otherwise, the service manual or Sams' for the set will be required unless their function of the relevant pot is obvious. * For service menus accessed via the remote control, service information is almost a necessity since adjustment procedures vary widely and it is all too easy to totally mess things up - even to the point of inflicting serious and expensive damage to the set. For information on accessing the service menus if used on your model, see the section: "Setup adjustments lost - TV service codes". However, even if the access procedure is known, get the service manual or Sams'! * If a computer interface is required, you can most probably forget about attempting to adjust anything unless you find a friendly shop to provide the adapter and walk you through the procedure. Why would they want to do this? Because they know you there is a good chance that you will have to pay them to unscramble the mess you created!
On a decent TV, you should be able to make out the individual scanning lines. If they are fuzzy, especially in bright areas, then focus may need to be adjusted. The focus pot is usually located on the flyback transformer or on an auxiliary panel nearby. Where there are two adjustment knobs on the flyback transformer, the top one is generally for focus and the bottom one is for G2. The focus wire usually comes from the flyback or the general area or from a terminal on a voltage the multiplier module (if used). It is usually a wire by itself going to the little board on the neck of the CRT. Let the set warm up for at least half an hour. Display a good quality signal. Turn the user color control all the way down and the brightness and contrast controls all the way up. This will be the worst case. Adjust the focus control for best overall sharpness - you may not be able to get it perfect everywhere - center as well as corners. If best focus is at one end of the focus pot's range and still not good enough, there may be a problem in the focus divider, focus pot, or some related component.
The screen should be adjusted with a white pattern (snow from the tuner should do or turn the user COLOR control all the way down to get a black and white picture). Put the set in Service mode (horizontal line) if it has such a switch in the back or inside. If not, just use the raster in a darkened room. Adjust screen for a dim white line (raster). If the line is not white at its dimmest point, you will need to adjust the drive and cutoff controls for R, G, & B. Alternatively, you can use the following procedure: Turn R, G, and B screen (or background) controls down. Now turn color control fully counterclockwise -- off. Now turn up red screen until the screen just shows a red hue. Now turn red gun down until red tint just goes away. Now do the same with the green and blue screen controls. Now adjust the two DRIVE controls for the best black and white picture. That`s all there is to it. I don`t like to work with just a thin "SETUP" line. Cartoons seem to be the best thing to have on while doing the above procedure. You can also use just plain snow (no program) if you prefer. If you can obtain a good b@w pic. when you`re done, the tube is good and the set if most likely functioning properly. Be patient and go slow while watching the large mirror that you are using during this procedure. (LEE)
For slight tweaks, the following is not necessary. However, if someone turned all the internal controls or if you are making significant changes that affect G2 (screen), then following the procedure below is desirable to achieve best performance and maximize life of the CRT. The typical user controls - brightness and contrast can, of course, be set arbitrarily, depending on video content and ambient lighting conditions. Set the user brightness and contrast controls in the middle for the following adjustments and let the set warm up for 20 minutes or so. (From: Jeroen H. Stessen (Jeroen.Stessen@ehv.ce.philips.com)). Now the screen control, that's another matter. It sets the voltage on the second grid of the electron guns, typically between +500 and +1000 V. You will want to use a well-isolated screwdriver for that if it is a naked potentiometer. In the old days there used to be 3 separate potentiometers for 3 G2s, now there is generally only one. Its purpose is to set the cutoff voltage for the guns, i.e. the voltage between K and G1 at which the beam is just off. The higher you set the VG2, the higher VK - VG1 must be to cut off the beam. If you set VG2 too low then your picture will be dark. You can compensate for that with the brightness control, which in effect will lower the VKs. A disadvantage is that you will not get optimum sharpness and peak brightness from your picture tube. If you set VG2 too high then your picture will be bright. You can compensate for that with the brightness control, which in effect will raise the VKs. You might even get retrace lines which can usually not be made to disappear with the brightness control. Another disadvantage is that you will not get optimum LIFETIME from your picture tube. With a too high cutoff voltage the cathode (electron emitting surface) will wear out too soon. You will need to see the picture tube specifications (or possibly the Sams' Photofact or service manual for the set --- sam) in order to find the correct setting for the cutoff voltage. This is measured as VK - VG1 (for each channel RGB) and is typically 130-160 V max. There will be spread between the 3 channels, typically the highest of the 3 measured values will be set against the upper limit. The usual adjustment procedure is as follows: * Use any low-level adjustments to set a black picture with all 3 cathode voltages at the specified level (e.g. 130 V) above the VG1 voltage (may be 0 V or 12 V or 20 V ?). (These are typically called RGB brightness, bias, or background level and are often on the little board on the neck of the CRT but not always --- sam). * Adjust VG2 (screen) until one colour just starts too light up, turn it back down until the screen is just black again. * Now adjust 2 of the 3 low-level black controls until the other 2 colours just light up, and then back to black again. * Select a white picture and use 2 low-level white (RGB drive or gain, also generally on the neck board --- sam) controls to set the proper colour temperature for white to your own taste. * Check your black calibration again, may have to iterate a bit.
Color balance needs adjustment if the highlights and/or shadows of a black and white picture (turn the color control all the way down) are not a perfectly neutral gray. Note: Some TV designs (Zenith uses this in a few models) automatically balance CRT cathode drive by sensing emission from the red, green, and blue guns using a gray scale reference pulse outside the viewable picture. If this is the case with your set, there may be no user OR service adjustments :-(. A color balance problem in this case means either a failure of this circuitry or a CRT where the emission from the 3 cathodes is so unbalanced (usually due to one being much much weaker than the others) that compensation is not possible. To adjust the color balance: Turn the color control all the way down so that you get what should be a B/W picture. Set the user brightness and contrast controls about mid-range. The tint control should not matter (if it does at this point, you have other chroma problems or an 'autocolor' switch is on limiting the range of some controls). Adjust the sub-brightness controls (may be called color screen, background, or the like) so that the dark areas of the picture are just visible and neutral gray. Then, adjust the color gain controls until the brightest areas are neutral white but not so bright that there is 'color bleeding' in the highlights. This should get you close. If something is still shifting after warmup and get some cold-spray or even a little blower and try to locate the component that is drifting. Most likely a transistor or capacitor.
Horizontal position may be set via a switch or jumper, a pot, or (mostly in B/W TVs) a set of rings on the CRT neck. Horizontal size should be set so that there is about 10-15 percent overscan left and right. This will allow ample margin for power line voltage fluctuations, component aging, and the reduction in raster size that may occur with some VCR special effects (fast play) modes. Many sets no longer have any horizontal size adjustments and depend on accurate regulation of the voltage to the horizontal output stage to control horizontal size. There may be a B+ adjustment to perform first. On those that do, the adjustment may either be done by setting the B+ voltage, by a pot, or a width coil in series with the horizontal deflection coils. Modern sets do not generally have any linearity control but you may find this on older models. You will need to go back and forth between size and linearity as these adjustments are usually not independent. Some of the newest sets control all these parameters via settings in non-volatile memory and use service menus accessed via the remote control for nearly all setup adjustments.
Vertical position may be set via a switch or jumper, a pot, or (mostly in B/W TVs) a set of rings on the CRT neck. Vertical size should be set so that there is about 10-15 percent overscan top and bottom. This will allow ample margin for power line voltage fluctuations, component aging, and the reduction in raster size that may occur with some VCR special effects (fast play) modes. Some sets no longer have any vertical size adjustments and depend on the accurate regulation of the voltage to the vertical output stage to control vertical size. On those that do, the adjustment is usually a pot in the vertical output circuitry. If your set has a linearity control, you will need to adjust this in conjunction with the size control as these are usually not independent. Some of the newest sets control all these parameters via settings in non-volatile memory and use service menus accessed via the remote control for nearly all setup.
There may be two controls - amplitude and phase. Pincushion amplitude as its name implies, controls the size of the correction. Pincushion phase affects where on the sides it is applied. Don't expect perfection. If the controls have no effect, there is probably a fault in the pincushion correction circuitry. It is best to make these adjustments with a crosshatch or dot test pattern
This refers to imperfections in the shape of the picture not handled by the pincushion and size adjustments. These types of defects include trapezoidal or keystone shaped raster and jogs or wiggles around the periphery of the raster. Unfortunately, one way these are handled at the factory is to glue little magnets to strategic locations on the CRT and/or rotate little magnets mounted on the yoke frame. Unless you really cannot live with the way it is (assuming there isn't something actually broken), leave these alone! You can end up with worse problems. In any case, carefully mark the position AND orientation of every magnet so that if this happens, you can get back to where you started. If the magnets are on little swivels, some experimenting with them one at a time may result in some improvement. Of course, it is best to obtain a service manual and follow its instructions.
Very simple - nothing is quite perfect. Perfect convergence is not even necessarily possible in theory with the set of adjustments available on a typical TV. It is all a matter of compromises. Consider what you are trying to do: get three electron beams which originate from different electron guns to meet at a single point within a fraction of a mm everywhere on the screen. This while the beams are scanning at an effective writing rate of 20,000 mph across the face of a 27" CRT in a variable magnetic environment manufactured at a price you can afford without a second mortgage!
Purity assures that each of the beams for the 3 primary colors - red, green, and blue - strikes only the proper phosphor dots for that color. A totally red scene will appear pure red and so forth. Symptoms of poor purity are blotches of discoloration on the screen. Objects will change shades of color when the move from one part of the screen to another. Convergence refers to the control of the instantaneous positions of the red, green, and blue spots as they scan across the face of the CRT so that they are as nearly coincident as possible. Symptoms of poor convergence are colored borders on solid objects or visible separate R, G, and B images of fine lines or images, Note: It is probably best to face the set East-West (front-to-back) when performing any purity and convergence adjustments. Since you probably do not know what orientation will eventually be used, this is the best compromise as the earth's magnetic field will be aligned mostly across the CRT. This will minimize the possible rotation of the picture when the unit is moved to its final position but there may be a position shift. Neither of these is that significant so it probably doesn't really matter that much unless you are super fussy. Of course, if you know the final orientation of the TV in your entertainment center - and you don't expect to be redecorating, use that instead. Or, plan to do the final tilt and position adjustments after the set is in position - but this will probably require access to the inside! First, make sure no sources of strong magnetic fields are in the vicinity of the TV - loudspeakers, refrigerator magnets, MRI scanners, etc. A nearby lightning strike or EMP from a nuclear explosion can also affect purity. Cycle power a couple of times to degauss the CRT (1 minute on, 20 minutes off) - see the section: "Degaussing (demagnetizing) a CRT". If the built in degaussing circuits have no effect, use an external manual degaussing coil. Assuming this doesn't help, you will need to set the internal purity and/or convergence adjustments on the CRT. Modern CRTs usually use a combination of a series of magnetized moveable rings on the neck, and yoke position and orientation to set purity and convergence. First, mark the positions of all adjustments - use white paint, 'White out', or a Magic Marker on the ring magnets on the neck of the CRT, the position and tilt of the deflection yoke, and any other controls that you may touch deliberately or by accident. However, if your set is still of the type with a drawer or panel of knobs for these adjustments, don't even think about doing anything without a service manual and follow it to the letter unless the functions of all the knobs is clearly marked (some manufacturers actually do a pretty good job of this). Note: some CRTs do not have any adjustable rings for purity (and static convergence). Either an internal structure in the neck of the CRT or an external 'permalloy' sleeve is permanently magnetized at the factory and there is not way of tweaking it in the field. However, it may be possible to use a normal set of magnet rings in addition to or in place of it to correct for purity or convergence problems due to loss of magnetism due to age or someone waving a 10 pound magnet near the CRT neck!
Purity on modern CRTs is usually set by a combination of a set of ring magnets just behind the deflection yoke on the neck of the CRT and the position of the yoke fore-aft. As always, mark the starting position of all the rings and make sure you are adjusting the correct set if rings! Use the following purity adjustment procedure as a general guide only. Depending on the particular model TV, the following purity adjustment procedure may substitute green for red depending on the arrangement of the guns in the CRT. This description is based on the Sams' Photofact for the RCA CTC111C chassis which uses a slot-mask CRT. The procedures for dot-mask and Trinitron (aperture grille) CRTs will vary slightly. See you service manual! Obtain a white raster (sometimes there is a test point that can be grounded to force this). Then, turn down the bias controls for blue and green so that you have a pure red raster. Let the set warm up for a minimum of 15 minutes. Loosen the deflection yoke clamp and move the yoke as far back as it will go, Adjust the purity magnets to center the red vertical raster on the screen. Move the yoke forward until you have the best overall red purity. Now, move the yoke forward until you have the best overall red purity. Tighten the clamp securely and reinstall the rubber wedges (if you set has these) to stabilize the yoke position. Reset the video adjustments you touched to get a red raster.
In the good old days when TVs were TVs (and not just a picture tube with a little circuit board attached) there were literally drawers full of knobs for setting convergence. One could spend hours and still end up with a less than satisfactory picture. As the technology progressed, the number of electronic adjustments went down drastically so that today there are very few if any. Unless you want a lot of frustration, I would recommend not messing with convergence. You could end up a lot worse. I have no idea what is used for convergence on your set but convergence adjustments are never quite independent of one another. You could find an adjustment that fixes the problem you think you have only to discover some other area of the screen is totally screwed. In addition, there are adjustments for geometry and purity and maybe others that you may accidentally move without even knowing it until you have buttoned up the set. Warning: Accurately mark the original positions - sometimes you will change something that will not have an obvious effect but will be noticeable later on. So it is extremely important to be able to get back to where you started. If only red/green vertical lines are offset, then it is likely that only a single ring needs to be moved - and by just a hair. But, you may accidentally move something else! If you really cannot live with it, make sure you mark everything very carefully so you can get back to your current state. A service manual is essential! Convergence is set using a white crosshatch or dot test pattern. If you do not have a test pattern generator, any static scene (from a camcorder or previously recorded tape, for example) with a lot of fine detail will suffice. Turn the color control all the way down so you have a B/W picture. Static convergence sets the beams to be coincident in the exact center of the screen. This is done using a set of ring magnets behind the purity magnets on the CRT neck. From the Sams' for the RCA CTC111C: "adjust the center set of magnets to converge blue to green at the center of the screen. Adjust the rear set of magnets to converge red to green at the center of the screen." Your set may have a slightly different procedure. Dynamic convergence adjusts for coincidence at the edges and corners. On old tube, hybrid, and early solid state TVs, dynamic convergence was accomplished with electronic adjustments of which there may have been a dozen or more that were not independent. With modern sets, all convergence is done with magnet rings on the neck of the CRT, magnets glued to the CRT, and by tilting the deflection yoke. The clamp in conjunction with rubber wedges or set screws assures that the yoke remains in position. From the Sams' for the RCA CTC111C: "Loosen the screws at the 6 o'clock and 10 o'clock positions to permit the yoke to be tilted vertically. Rock yoke up and down to converge the right and left sides of the screen. Tighten screw at 6 o'clock and loosen screw at 3 o'clock to permit the yoke to be tilted horizontally. Rock yoke from side to side to converge the top and bottom of the screen. Tighten screws at 3 o'clock and 10 o'clock." Many sets simply use the main clamp which locks the yoke to the neck of the CRT in conjunction with rubber wedges between the yoke and the funnel of the CRT to stabilize the yoke position position. Refer to your service manual. (Is this beginning to sound repetitious?) For additional comments on convergence adjustments, see the sections: "Tony's notes on setting convergence on delta gun CRTs" and "Saga and general setup for large CRT TVs".
You have just noticed that the picture on your fancy (or cheap) TV is not quite horizontal - not aligned with the front bezel. Note that often there is some keystoning as well where the top and bottom or left and right edges of the picture are not quite parallel - which you may never have noticed until now. Since this may not be correctable, adjusting tilt may represent a compromise at best between top/bottom or left/right alignment of the picture edges. You may never sleep again knowing that your TV picture is not perfect! BTW, I can sympathize with your unhappiness. Nothing is more annoying than a just noticeable imperfection such as this. However, since TVs always overscan, the only time you will really notice a minor tilt without going out of your way to look for it is if there is text or graphics near the edge of the screen. There are several possible causes for a tilted picture: 1. Set orientation. The horizontal component of the earth's magnetic field affects this slgithly. Therefore, if you rotate the TV you may be able to correct the tilt. Of course, it will probably want to face the wall! Other external magnetic fields can sometimes cause a rotation without any other obvious effects - have you changed the TV's location? Did an MRI scanner move in next door? 2. Need for degaussing. Most of the time, magnetization of the CRT will result in color problems which will be far more obvious than a slight rotation. However, internal or external shields or other metal parts in the set could become magnetized resulting a tilt. More extensive treatment than provided by the built-in degaussing coil may be needed. Even, the normal manual degaussing procedure may not be enough to get close enough to all the affected parts. 3. You just became aware of it but nothing has changed. Don't dismiss this offhand. It is amazing how much we ignore unless it is brought to our attention. Are you a perfectionist? 4. There is an external tilt control which may be misadjusted. Newer Sony monitors have this (don't know about TVs) - a most wonderful addition. Too bad about the stabilizing wires on Trinitron CRTs. A digital control may have lost its memory accidentally. The circuitry could have a problem. 5. There is an internal tilt control that is misadjusted or not functioning. The existance of such a control is becoming more common. 6. The deflection yoke on the CRT has gotten rotated or was not oriented correctly at the time of the set's manufacture. Sometimes, the entire yoke is glued in place in addition to being clamped adding another complication. If the TV was recently bumped or handled roughly, the yoke may have been knocked out of position. But in most cases, the amount of abuse required to do this with the yoke firmly clamped and/or glued would have totally destroyed the set in the process. There is a risk (in addition to the risk of frying yourself on the various voltages present inside as operating TV) of messing up the convergence or purity when fiddling with the yoke or anything around it since the yoke position on the neck of the tube and its tilt may affect purity and convergence. Tape any rubber wedges under the yoke securely in place as these will maintain the proper position and tilt of the yoke while you are messing with it. (Don't assume the existing tape will hold - the adhesive is probably dry and brittle). 7. The CRT may have rotated slightly with respect to the front bezel. Irrespective of the cause of the tilt, sometimes it is possible to loosen the 4 (typical) CRT mounting screws and correct the tilt by slightly rotating the CRT. This may be easier than rotating the yoke. Just make sure to take proper safety precautions when reaching inside!
These tend to be a lot simpler and less critical than for color monitors or TV sets. On a B/W TV you will probably see some of the following adjustments: 1. Position - a pair of rings with tabs on the neck of the CRT. There may be electronic position adjustements as well though this is not that common on small TVs. 2. Width and height (possibly linearity as well) controls. There may be some interaction between size and linearity - a crosshatch test pattern is best for this. Vertical adjustments are almost always pots while horizontal (if they exist) may be pots and/or coils. Size will normally be set for 5-10% overscan to account for line voltage fluctuations and component drift. Confirm aspect ratio with test pattern which includes square boxes. 3. Geometry - some little magnets either on swivels around the yoke or glued to the CRT. If these shifted, the the edges may have gotten messed up - wiggles, dips, concave or convex shapes. There may be a doxen or more each mostly affecting a region around the edge of the raster. However, they will not be totally independent. Check at extremes of brightness/contrast as there may be some slight changes in size and position due to imperfect HV regulation. There may be others as well but without a service manual, there is no way of knowing for sure. Sams' often has folders for B/W TVs. Just mark everything carefully before changing - then you will be able to get back where you started.
TVs require a variety of voltages (at various power levels) to function. The function of the low voltage power supply is to take the AC line input of either 115 VAC 60 Hz (220 VAC 50 Hz or other AC power in Europe and elsewhere) and produce some of these DC voltages. In all cases, the power to the horizontal output transistor of the horizontal deflection system is obtained directly from the low voltage power supply. In some cases, a variety of other DC voltages are derived directly from the AC line by rectification, filtering, and regulation. In other designs, however, most of the low voltages are derived from secondary windings on the flyback (LOPT) transformer of the horizontal deflection system. In still other designs, there is a separate switchmode power supply that provides some or all of these voltages. There are also various (and sometimes convoluted) combinations of any or all of the above. There will always be: 1. A power switch, relay, or triac to enable main power. 2. A set of rectifiers - usually in a bridge configuration - to turn the AC into DC. Small ceramic capacitors are normally placed across the diodes to reduce RF interference. 3. One or more large filter capacitors to smooth the unregulated DC. In the U.S., this is most often a voltage around 150-160 V DC. In countries with 220 VAC power, it will typically be around 300-320 V DC. 4. A discrete, hybrid, or IC regulator to provide stable DC to the horizontal deflection system. Sometimes feedback from a secondary output of the flyback or even the high voltage is used. This regulator may be either a linear or switching type. In some cases, there is no regulator. 5. Zero or more voltage dividers and/or regulators to produce additional voltages directly from the line power. This relatively rare except for startup circuits. These voltages will not be isolated from the line. 6. A degauss control circuit usually including a thermistor or Posistor (a combination of a heater disk and Positive Temperature Coefficient (PTC) thermistor in a single package). When power is turned on, a relatively high AC current is applied to the degauss coil wrapped around the periphery of the CRT. The PTC thermister heats up, increases in resistance, and smoothly decreases the current to nearly zero over a couple of seconds. 7. A startup circuit for booting the horizontal deflection if various voltages to run the TV are derived from the flyback. This may be an IC or discrete multivibrator or something else running off a non-isolated voltage or the standby power supply. 8. A standby power supply for the microcontroller and remote sensor. Usually, this is a separate low voltage power supply using a small power transformer for line isolation. Always use an isolation transformer when working on a TV but this is especially important - for your safety - when dealing with the non-isolated line operated power supply. Read and follow the information in the section: "Safety guidelines".
The partial schematic below is similar to those found in the majority of
TVs sold in countries with 110 to 120 VAC power. Many parts are not shown
including the power switch or relay, RFI bypass capacitors across the
rectifier diodes, and RFI line filter.
Bypass resistor
Line fuse Main bridge Fusable +----/\/\-----+
_ rectifier resistor | +-----+ |
H o--_ --+------|>|---+---/\/\--+---+---| REG |---+---+---o B+
| | | +-----+ |
| +---|>|---+ C1 _|_ Main | _|_ Regulator
115 VAC | | 400 uF --- filter | --- output
+--|---|<|---+ 200 V | cap | | capacitor
| | | | |
+-> N o---------+---|<|---+---------+----------+----------+---o Non-isolated
| return
+-> G - Power line earth ground via building wiring
* The line fuse is typically 2 to 4 A, usually a normal fast blow type. Even
so, it may not blow as a result of faults down the line - the fusable
resistor or regulator may fail first.
* The main bridge rectifier is often composed of 4 discrete diodes (similar to
1N400Xs) but may also be a single unit. Failures - usually shorted diodes -
are common.
* The main filter capacitor can range in size from 200 to 800 uF or more
at 200 to 250 V. THIS CAN BE LETHAL! A typical TV may continue to work
at normal line voltage without any noticeable degradation in performance
(hum bars, hum in sound, or shutdown) even if this capacitor is reduced
in value by 75%. Its uF value is therefore not critical.
* The regulator is often an IC or hybrid module. Failures resulting in no
or reduced output, or no regulation are common.
* The regulator output capacitor is needed for the B+ regulator to function
properly. If this capacitor is reduced in value or develops a high ESR,
regulation may fail resulting in instability, oscillation, or excessive
B+ and shutdown.
* The regulator bypass resistor reduces the amount of current control needed
of the regulator. Caution: even if the regulator has been pulled, the B+
line will have substantial voltage as a result of this resistor.
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