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This may be a slight drift - like someone is messing with the fine tuning or such a substantial change in tuning frequency that the channels go by as though you are surfing. Possible causes depend on tuner type: 1. Quartz tuner (10 button direct access digital synthesizer) - For a slight drift, a component is probably changing value, possibly the crystal in the reference oscillator. For gross changes - flipping through channels - it is more likely to be a digital control problem - the microcontroller is misdirecting the synthesizer to change frequency. 2. Varactor tuner (buttons but not direct channel access) - If only a single pushbutton selection is the problem, the the varactor tuning diode for that button is probably changing capacitance. If all channels in a band (Vl, Vh, U) are having a problem, it is more likely to be a drifting D/A or faulty AFT (Automatic Fine Tuning) circuit or power supply. 3. Turret or switch tuner (Knobs) - A component like a capacitor is changing value. You will have to get in there with a heat gun or cold spray and track it down the old fashioned way. At least, the problem is almost certainly localized to the tuner box (and possibly the controller if applicable). As noted, gradual slight changes in tuning are likely due to frequency determining components drifting. Uncontrolled channel surfing is probably a logic problem. For the quartz tuner, this could still be marginal connections causing the microprocessor to misdirect the synthesizer to change channels. For the latter case, particularly, the cause may still be bad connections resulting in loss of channel memory and/or erratic behavior.
When a bright scene comes, the screen flashes and there is a lot of noise in the sound. When a dark scene comes, there is no flash or noise. Changing channel does not help. The noise persists even when the sound is muted. (The following is from: Lattuca@Midwest.net (Sam Lattuca)) When the video detector level is adjusted too high, you will get noise in the sound while screen contains a lot of white information (i.e. letters) but won't when only dark scenes are present. The video level adjust is usually a small coil normally located near the IF section. Since your set is several years old, this wouldn't be uncommon. It can be adjusted while watching the picture and listening to the sound.
(From: Mr. Caldwell (jcaldwel@iquest.net)). On virtually all newer televisions and in particular Mitsubishi televisions there is a problem with interference being emitted by the switched mode power supply. The common symptom of this 'fault' is snake like dotted 'S' lines on channels 2-6. It doesn't matter if it's cable, antenna or satellite(channel 3/4), this symptom can occur. The common cause of this interference being allowed into the tuner is cabling. The super cheap 'suitable for garbage tie' cable that comes with even the most expensive VCR's is the culprit in most cases. The second is a set of rabbit ears the least common is an open or high resistance to ground connection (usually at a connector) on the incoming cable line. To fix this there is only one reliable solution. All cabling must be hand made RG-6 cable. Make as follows: * Strip the outer sheath of the cable to expose the braid and *fold the braid* away from the end so that it covers the unstripped outer braid. * Strip the inner conductor to it's proper length. * Install a good quality RG-6 connector *over the folded* braid. * Crimp with the proper RG-6 attachment to the cable crimpers, don't use a set of pliers or other -crushing- device. If the cable company doesn't water proof the outside connectors, Radio Shack sells a 'sealing tape' just for this purpose. Most cable companies use self sealing 'o-ring' connectors. (From: Jeroen H. Stessen (Jeroen.Stessen@ehv.ce.philips.com)). There is also interference from internal microprocessors and digital text generators (on-screen display, close captioning, teletext). And with 100 Hz digital television there is a wealth of sources ... Using only high quality shielded cable as described above seems like really good advise, FWIW I'd like to second that. I wish that everyone would take antenna cables as seriously as you. Generally, double-braided cable (using copper foil for second shield) and coaxially constructed connectors are recommended. But I think that the hand-mountable F-type connectors (Radio Shack) would be equally good, though less robust, if mounted properly. As far as antennas go, a decent rooftop antenna should always be better than whatever rabbit ear construction you might think of. In this case, distance counts too, the antenna WILL pick up interference.
So you bought a high performance TV and a set of $20.00 rabbit ears and there are lines on channels 2-6. Go buy a set of rabbit ears that has *only* a coax connector on the back, throw the cable supplied with it in the bin for 'twist ties'. Also buy an inexpensive surge suppressor that has a cable protector, enough RG-6 cable and connectors for two cables. * Make one cable long enough to get the antenna away from the set (12ft) and the other to connect the antenna to the surge suppressor. * Connect the long cable to the set and the other end to the surge suppressor. * Find an outlet away from the set and plug the surge suppressor in (pick the most sane order for all of this.) * Connect the shorter cable to the surge suppressor and connect the other end to the antenna. You're done and if you thought carefully you would have put the antenna near your easy chair so you can adjust the picture or put the antenna where you'll get the best reception and prevent interference. The surge suppressor was needed to ground the other end of the coax so as not to make the outer shield an antenna for the interference from the TV's power supply. This method can also help allevate 'dead spots' when using rabbit ears.
(From: Isaac Bergen (isaac.bergen@sympatico.ca)). Could be interference. If the pattern slowly moves up the screen, the problem is from the 60 Hz power. A line of dots or thin lines usually means corona discharge (arcing) from a nearby power line (especially on humid days). Could also be from a bad filter capacitor in the TV's power supply. A "checkered" pattern could be from a digital type noise source like a computer, etc. If you move the TV to another room and the interference changes, that's probably it. EM or RFI hell? -------------- "About a mile from my home there are four TV (channels 2, 4, 9 and 14) and several broadcast FM transmitters, all working with powers in the 100+ Kw ERP class. Radio reception is a nightmare, mostly (I think) because of IM products in overloaded front end stages. In most bands there are several regions at a spacing of about 100 Khz, each 30 to 40 Khz wide with a harsh buzz stronger than anything else." (From: Don Klipstein (don@Misty.com)). If the buzz is of a frequency like the power line frequency or a harmonic thereof, then the nearby transmitters may not be the culprit. Instead, nearby corona on a high voltage power line, a nearby neon sign, or a nearby light dimmer may be the offender. Although the noise from these is usually broad-band, the noise could get concentrated into bands spaced 100 KHz apart if something resonant around 100 KHz is involved in the noise production. I would try temporarily turning off all fluorescent lights, neon signs, lights with dimmers, etc. and asking your neighbors to do the same to see if any of these is the offender. I have often found light dimmers to be major RF noise sources. Possibly, an RF noise filter for the AC power for your receiver may help things. If you isolate a single offending appliance, it may help to plug it into an RF noise filter. If you use any filters with either the offending appliance or the receiver, try all combinations of plug reversal to see what works best. Both leads of any offending appliance may not equally spew noise, and both lines in the filter may not equally block noise. Both lines of the receiver's power cord may not equally bring noise into the receiver, if this is the route the noise takes.
First check that any muting control is not activated. This might be a button on the remote or set itself. If you have a headphone jack, it may have dirty contacts as plugging in a headphone usually mutes the speaker. If the set is mono or only one channel of a stereo set is out, then check for bad connections to the loudspeaker. Test the loudspeaker by disconnecting one of the wires (with the power off!) and measuring its resistance with an ohmmeter (it should be less than 100 ohms - probably less than 8 ohms). Or momentarily touch a 1.5 volt battery to the speaker terminals - you should get a click or pop from the speaker. Next, trace back from the speaker output terminals to the circuit board and look for bad solder connections or a loose or dirty connector. If these tests do not reveal anything, you probably need a scope (or audio signal tracer) and schematic. Or at least the part number off of the chip. Is the final amp a chip also or just a transistor? Have you tested the transistor? If there is little or no buzz from the speaker, that would indicate a problem fairly near the output. If the tuner/if were bad, I would expect some noise/humm pickup from the low level audio stages. Get the part number off of the chip. If it is in a socket, check the contacts for corrosion or looseness.
Assuming you are not attempting to play it at ear shattering levels, this may be due to an alignment problem in the IF/audio demodulator, a bad audio IC or other circuitry, bad connection, or a defective speaker. If your TV has an earphone or audio line out jack, try this to see if it is clear. If so, then your problem is in the final audio amp or speaker(s). If only one channel of a stereo TV is affected, it is almost certainly the audio amp or speaker for that channel. Interchange connection to the two speakers temporarily and see if the problem moves. If the problem is at all intermittent - try gently whacking the TV - then it is likely a bad connection - either a cold solder joint or a dirty or tired IC socket. The audio amplifiers in newer TVs are almost always ICs and replacements are usually readily available. If the IC is in a socket, remove the IC, clean the pins and socket contacts and reinstall it. Sometimes, the contacts on old socket lose their springiness and do not provide solid connections. Such a socket will need to be replaced. If the set uses discrete transistors, it s also possible for one of these to become noisy. If your TV is fairly old - 10 years or so - this may be an alignment problem requiring tweaking of a coil in the sound IF. See your service manual. It may be possible to have similar problems with newer TVs but this is relatively rare.
Do you actually mean buzz - low frequency as in 60 Hz? Or, do you really mean high pitched whine. If the latter, see the section: "High pitched whine or squeal from TV with no other symptoms". Or, it may be a combination of both effects. Is the buzz through the speaker or from the inside of the set? * If it is the speaker, then it is a problem with the audio circuitry. This could be a design issue - very common or an actual fault (if it wasn't there before). It could also be interference caused by fluorescent lights or appliances like vacuum cleaners with universal motors or body massagers with vibrator interrupters (which generate sparks). Where the source of the problem cannot be located or eliminated, consider using a (HiFi) VCR for the tuner with an external stereo amplifier and the disable the internal speaker. * There is a slight possibility that the AC power in your house has some harmonic content - the waveform is not sinusoidal. This might be the case if you try to run on the same circuit as an active dimmer or something else with thyristor control. Proximity to heavy industry could also cause this. Relocating the offending device to another branch circuit may help. You could also try a line conditioner (not just surge suppressor) which includes filtering. Or, use a HiFi VCR as your audio source (see above). Else, petition to have that metal foundry move out of the neighborhood :-). * However, a buzzing that only occurs when the picture has sharply defined text or graphics, may be an overload problem at the source - some TVs simply handle it better than others. If it is a fault in the TV, an adjustment to the tuner or IF may be needed. (From: Paul Weber (webpa@aol.com)). Not to disparage proponents of the evil demon theory, but the phenomenon is more commonly known as "sync buzz". It is caused by poor performance in the TV's audio circuitry. It can usually be fixed by (1) reducing the signal strength and/or (2) tweaking the sound IF coil. Unfortunately, some of the latest TV receivers have no sound IF coil to adjust. If your TV has a sound IF coil, it can be done by ear, if you don't care about sound quality. However,I'd recommend taking it so a competent shop and describing the symptoms. Use the term "sync buzz in the audio," and they'll know what you mean. Be advised that it can't be cured in some TVs due to poor design. * If it is from inside the set (and not from the speaker), it is in the deflection (probably vertical) or power supply. Either of these can vary in severity with picture content due to the differing current requirements based on brightness. It could be a power supply transformer, deflection yoke, or other magnetic component. Even ferrite beads have been caught buzzing when no one was looking :-). Any of these parts could vibrate if not anchored securely or as they loosen up with age. Some hot-melt glue, RTV silicone, or even a strategically wedged toothpick may help. A new part may or may not quiet it down - the replacement could be worse! See the section: "Reducing/eliminating yoke noise". * Some TVs are simply poorly designed. You cannot infer the severity of this annoyance from any specifications available to the consumer. It is strictly a design (e.g. cost) issue. The size of the TV is not a strong indicator of the severity of the problem but there will be some relationship as the power levels are higher for larger sets. The best you can do is audition various TVs very carefully to find one that you are satisfied with. BTW, when I got my new super-duper RCA Colortrak in 1980, it had a similar annoying buzz - even had a repair guy out who behaved as though this was to be expected. I did get used to it and am not even aware of it today - and still use that set. Additional comments: (From: Karen (kclark9835@aol.com)). Also for some audio buzz problems especially in the older units don't overlook the possibility of a misaligned trap. or a touch-up of the sound discriminator may prove helpful. (From: Alan (algba@ix.netcom.com)). If the buzz is coming from the speaker suspect a bad saw filter in the if circuit (very common). If it is coming from elsewhere in the set it could be the flyback transformer, line input choke, or most common on those sets - the deflection yoke. I have repaired many of these yoke by using a wooden shim and some silicone rubber. In the collar of the yoke just ahead of the lock down clamp, there are some metal strips under the plastic. These are magnet that are used for convergence correction at the top and bottom of the picture. If you disturb them too much it will throw off the convergence.
First, make sure it is not coming from the loudspeaker itself. If it is, then we are looking at an unusual electronic interference problem rather than simply mechanical vibration. If it is a new set and think the sounds will drive you insane, returning it for a refund or replacement may be best alternative. However, you may get used to it in time. I don't know about returning a set to a store that doesn't take refunds (I won't even ask about that!). In most cases, this sound, while annoying, does not indicate an impending failure (at least not to the set - perhaps to your mental health) or signify anything about the expected reliability of the set though this is not always the case. Intermittent or poor connections in the deflection or power supply subsystems can also result in similar sounds. However, it is more likely that some part is just vibrating in response to a high frequency electric current. There are several parts inside the TV that can potentially make this noise. These include the horizontal flyback transformer, deflection yoke, other transformers, even ferrite beads in the horizontal deflection circuits. In addition, transformers or chokes in the switching power supply if this is distinct from the horizontal deflection circuitry. You have several options before resorting to a 12 pound hammer: * As much as you would like to dunk the TV in sound deadening insulation, this should be avoided as it will interfere with with proper cooling. However, the interior of the entertainment center cabinet can be lined with a non-flammable sound absorbing material, perhaps acoustic ceiling tiles. Hopefully, not a lot of sound energy is coming from the front of the set. * Move the TV out of a corner if that is where it is located - the corner will focus sound energy into the room. * Anything soft like carpeting, drapes, etc. will do a good job of absorbing sound energy in this band. Here is your justification for purchasing those antique Persian rugs you always wanted :-). If you are desperate and want to check the inside of the set: * Using appropriate safety precautions, you can try prodding the various suspect parts (flyback, deflection yoke, other transformers), even lowly ferrite beads, with an insulated tool such as a dry wooden stick. Listen through a cardboard tube to try to localizing the source. If the sounds changes, you know what part to go after. * Once you have located the guilty party, some careful repositioning, a strategically wedged wooden toothpick, or a dab of RTV silicone or hot-melt glue may keep it quiet. Where the yoke is the guilty party, see the section: "Reducing/eliminating yoke noise". * It is possible to coat the flyback transformer, but this is used mostly when there a loose core or windings and you are getting not only the 15,735 Hz horizontal (NTSC) but also various subharmonics of this. This is probably acceptable but may increase the temperature of the flyback. * A replacement flyback (or whatever part) may cure the problem unless it is a design flaw or manufacturing quality problem. However, the replacement part could be noisier. You really do not want to replace the yoke (aside from the cost) as convergence and other service adjustments would need to be performed. Other transformers can be replaced. Note that the deflection frequency - just over 15 KHz for NTSC and PAL - is on the border of audible for adults but will likely be loud to younger people possibly to the point of being terribly annoying - or worse. If you are over 40 (men more so than women), you may not be able to hear the fundamental at all (at least you can look forward to silence in the future!). So, even sending the TV back for repair may be hopeless if the technician cannot hear what you are complaining about! BTW, if you have a really old tube type TV, the power tubes (damper and horizontal output) can also whine but these sets are few and far between these days :-).
(From: Terry DeWick (dewickt@esper.com)). Carefully look under vertical core next to plastic liner, on top and bottom is a plate called the astigmatism shunt, it has come loose. Work RTV, epoxy, or service cement onto it to glue it down and noise should quit. (From: TVman (tvman@newwave.net)). I have fixed a total of 27 of these sets with noisy yokes by removing the yokes and using motor armature spray sealant. If you carefully mark the EXACT position of everything (yoke, purity magnets), and slide the yoke off the CRT, then once the yoke has been sealed with motor armature spray sealant and has dried thoroughly, put the yoke back EXACTLY where it was, there should be no problems. The only thing I have had to do was set the purity on one set, but it was off a little to begin with.
Many TVs actually run their switchmode power supplies even when off to power the standby stuff like the remote control receiver, real time clock or timer, and channel memory. Depending on the design of the regulator, the power supply may be running at a low chopper frequency due to the light load. Some people, dogs, and rodents are then annoyed. It could also be an indication of a fault like a bad capacitor or loosened transformer core if this symptom just developed - your hearing isn't likely improving :-(. There is so much running nowadays in 'off' electronics!
You press VOLUME UP and the channel changes or a setup menu appears all by itself just at the climax of your mystery story. Before you break out the screwdriver (or 12 pound hammer), cover up the IR remote sensor. Some types of electronic ballasted fluorescent lights may confuse the remote control receiver. Someone or something may be sitting on the remote hand unit or it may be defective and continuously issuing a bad command. Or, the kids across the street may have nothing better to do than to drive your TV (and you) nuts with their remote! There is also a slight chance power line interference (from a light dimmer or external sources) may result in similar symptoms. See the section: "Wiring transmitted interference". Assuming this is not the source of the problem: Check for bad connections - see if gently whacking the TV makes any difference or triggers the errant behavior. Bad connections in the power supply, system controller, or tuner, may result in this sort of behavior. See the section: "TV and Monitor Manufacturing Quality and Cold Solder Joints". See the sections and separate documents on problems with RCA/GE/Proscan and Sony TVs if yours is made by one of these companies. A microcontroller or other electronic problem is also possible. If the symptoms only develop after the set warms up, it may be heat related (though simple bad connections are more likely). Use 'circuit chiller' or a heat gun to identify the bad part.
The power that comes from the wall outlet is supposed to be a nice sinusoid
at 60 Hz (in the U.S.) and it probably is coming out of the power plant.
However, equipment using electric motors (e.g., vacuum cleaners), fluorescent
lamps, lamp dimmers or motor speed controls (shop tools), and other high power
devices, may result in a variety of effects.
While TVs normally include some line filtering, the noise immunity varies.
Therefore, if the waveform is distorted enough, some effects may show up even
on a high quality TV.
Symptoms will usually be one or two areas of noise moving slowly up the screen.
The source is probably local - in your house and probably on the same branch
circuit - but could also be several miles away.
* The rate will be the difference between the power line frequency (60 Hz in
the U.S.) and the scan rate (59.94 Hz for NTSC). This results in a drift of
about 16 seconds for a complete cycle (8 seconds if the inteference is at
120 Hz).
- A single bar would indicate interference at the power line frequency.
- A pair of bars would indicate interference at twice the power line
frequency.
Either of these are possible.
* Try to locate the problem device by turning off all suspect equipment to see
if the problem disappears.
* The best solution is to replace or repair the offending device. In the
case of a light dimmer, for example, models are available that do a better
job of suppressing interference than the typical $3 home center special.
Appliances are supposed to include adequate noise suppression but this is
not always the case.
If the source is in the next county, this option presents some significant
difficulties :-).
* Plugging the TV into another outlet may isolate it from the offending device
enough to eliminate or greatly reduce the interference.
* The use of a line filter may help. A surge suppressor is NOT a line filter.
* Similar symptoms could also be produced by a defective power supply in the
TV or other fault. The surest way of eliminating this possibility is to try
the TV at another location.
If you have eliminated other possibilities such as electromagnetic interference from nearby equipment or a faulty video cable or problems with the video input (e.g., cable or VCR) - then noisy or fluctuating AC power may be a possibility. However, most modern TVs usually have well regulated power supplies so this is less common than it used to be. Then again, your TV may just be overly sensitive. It is also possible that some fault in its power supply regulator has resulted in it becoming more sensitive to small power fluctuations that are unavoidable. One way to determine if the problem is likely to be related to AC power is to run the TV on clean power in the same location connected to the same video input. For example, running it on an Uninterruptible Power Source (UPS) with the line cord pulled from the wall socket would be an excellent test. The output of the UPS's inverter should be free of any power line noise. If the TV's image has now settled down: 1. Large appliances like air conditioners, refrigerator, or washing machines on the same circuit might cause significant power dips and spikes as they cycle. Plugging a table lamp into the same outlet may permit you to see any obvious fluctuations in power. What else is on the same circuit? Depending on how your house or apartment is wired, the same feed from the service panel may be supplying power to widely separated areas. 2. For some unfathomable reason, your TV may just be more sensitive to something about the power from the circuit in that room. There may be nothing actually wrong, just different. While unlikely, a light dimmer on the same circuit could be producing line-conducted interference. If you have a multimeter, you could at least compare the voltages between the location where it has problems and the one where it is happy. Perhaps, the TV is sensitive to being on a slightly different voltage. This might only be a problem if some circuitry in the the TV is marginal in some respect to begin with, however. 3. There could be a bad connection somewhere on the circuit. If your house has aluminum wiring, this is a definite possibility. Try a table lamp since its brightness should fluctuate as well. This should be checked out by a competent electrician as it represents a real fire hazard. An electrician may be able to pinpoint the cause but many do not have the training or experience to deal with problems of this sort. Certainly, if you find any power line fluctuations not accounted for by major appliances, on the same circuit this should be checked by an electrician.
You have sent the TV for repair and now three times, it blows something the instant anything is connected to it in your house. Other A/V equipment operates fine. Assuming all the other stuff is plugged into the same outlet asn is 115 VAC equipment and that thsi happens instantly when the TV is connected: Next time they bring it back, measure the voltage between the A/V connector shields and the shields on your cables - I wouldn't be surprised to find some substantial fraction of 115 VAC between them. This would mean that there is an internal short in the TV (their problem - any competent service center will routinely check for signal-AC ground shorts) resulting in a connection between the non-isolated AC ground and the signal ground. When you connect your equipment, you complete a path which results in a short circuit. Depending on the design of the TV and where the fault lies, much more than a simple fuse may be destroyed. This is similar to connecting a scope probe ground to a live chassis TV - see the section: "Safety guidelines".
You turn on your TV and 5-10 seconds later, the display is shaking or vibrating for a second or so. It used to only occur when first turned on, but now, the problem occurs 3 times in 30 seconds. Of course, many variations on this general theme are possible. Some possibilities: 1. External interference - did you change anything or move your A/V setup recently? Do you have a computer monitor nearby? 2. Defective circuitry in TV - power supply regulation, deflection, or bad internal connections are possible. 3. Defective video cable (unlikely) - wiggle the cables to be see if you can induce the problem. Note that many of the sources of electromagnetic interference that are problems with computer monitors like transformers and power lines will not cause noticeable shaking, wiggling, or jiggling on a TV because the power line and vertical scan are at almost exactly the same frequency and any such movement would be very slow.
When the set is first turned on, it works fine for about 20-30 seconds, then the picture goes away - all but about 1 inch of picture all around the outer edge of the screen. The square ring of picture that is left, is dim but otherwise normal. (The following from: (jack haney) jhaney@pacifier.com)) If this is a newer set, this sounds very much like a "closed caption" box for a captioning system not being used in your area. Newer Mitsubishis do much the same thing. If the wrong caption type is selected inadvertantly, all you'll see is a large black box on screen taking up about all but an inch each way.Try turning off all closed caption. The first time I saw this I looked like a damn fool in front of a customer, took me 30 minutes to figure it out.
"I noted the advertsing programs put in bright several frames of overshooting white signals in purpose of attracting attention which I do not want also it gets on my nerves sometimes. *flash* *flash* Ughhh! Is there a way to cutoff the "overload" or tone down that?" (From: Jeroen H. Stessen (Jeroen.Stessen@ehv.ce.philips.com)). Technically, the TV takes care of its own overload protection. Or at least it *should*, on some TV's you will certainly observe the line transformer going into saturation for a while. Other than that there is not much you can do, each TV should represent its input signals with as much fidelity as possible. Change channels? (I already suggested not watching :-). --- sam).
"I've seen this sort of thing on a TV I bought a couple of years ago. I only see it when Proctor & Gamble ads are on. The newer TVs are required to have Closed Caption decoding (CCD). My TV has an OFF-ON button for CCD. It also has a button labeled CH1-CH2. When pushed in I get the verbal text on the screen like I should. When the button is out, I get the funny codes from Proctor & Gamble." (From: Tim (jollyrgr@mc.net)). The code you are seeing is Closed Caption 2. My Zenith has CC 1, 2, 3, 4, as well as Text 1, 2, 3, and 4. I have seen CC 1 which is the normal closed captions. CC 2 is used for commercial logging/identification. There should be a way to completely turn off the captions. The TV, as you state, has a switch for turning off the captions and should solve your problem.Go to [Next] segment
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