TV SOUND SECTION PROBLEMS AND SOLUTIONS

Weak or distorted audio:
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 isrelatively rare.



Picture fine, no audio :

First check that any muting control is not activated. This might bea button on the remote or set itself. If you have a headphone jack, itmay have dirty contacts as plugging in a headphone usually mutesthe speaker. If the set is mono or only one channel of a stereo set is out, thencheck for bad connections to the loudspeaker. Test the loudspeaker bydisconnecting one of the wires (with the power off!) and measuring itsresistance with an ohmmeter (it should be less than 100 ohms - probablyless than 8 ohms). Or momentarily touch a 1.5 volt battery to the speakerterminals - you should get a click or pop from the speaker. Next, trace back from the speaker output terminals to the circuit boardand look for bad solder connections or a loose or dirty connector. If these tests do not reveal anything, you probably need a scope (oraudio signal tracer) and schematic. Or at least the part number off ofthe chip. Is the final amp a chip also or just a transistor? Have youtested 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 werebad, 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.



Weak or distorted audio:
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 itis 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 theAudio amp or speaker for that channel. Interchange connection to the two Weak or distorted audio 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 itis 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 theaudio 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 - thenit is likely a bad connection - either a cold solder joint or a dirtyor 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 theseto 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.

Buzzing TV :
Do you actually mean buzz - low frequency as in 60 Hz? Or, do youreally mean high pitched whine. If the latter, see the section:High pitched whine or squeal from inside TV. Is the buzz through the speaker or from the inside of the set? If it is the speaker, then it is a design issue with the audio circuitry.However, a buzzing that only occurs when the picture has sharply definedtext or graphics, may be an overload problem at the source - some TVssimply handle it better than others. If it is from inside the set, it is in the deflection or power supply. There is a slight possibility that the AC power in your house has someharmonic 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. In neither case can you infer the severity of this annoyance from specs.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. Possibly running on a slightly different line voltage may change it butthat is not really an option. You could try a line conditioner (notjust surge suppressor) which includes filtering. I suspect it won't make must difference. If it is in the audio circuits - from the speakers or line out - thenconsider using a (HiFi) VCR for the tuner with an external stereo ampand the internal speaker disabled. If it is noise from the TV, then the best you can do is audition variousTVs 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 ton be expected. I did get used to it and am not even aware of it today – and still use that set.



High pitched whine or squeal from TV with no other symptoms :
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. There are several parts inside the TV that can potentially make this noise - the horizontal flyback transformer and to a lesser extent, the deflection yoke would be my first candidates. In addition, transformers or chokes in the switching power supply if this is distinct from the horizontal deflection circuitry. I don't know about returning a set to a store that doesn't take refunds (I won't even ask about that!) but assuming that this sound level is normal for the particular model here are a couple of suggestions: You do not want to coat the TV as this may interfere with proper cooling, but the interior of the entertainment center cabinet could be lined with a non-flammable sounds 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 cornerwill focus sound energy into the room. Anything soft like carpeting, drapes, etc. will do a good job ofabsorbing sound energy in this band. If you are desperate and want to check the inside of the set: It is possible to coat the flyback transformer, but this is used mostlywhen there a loose core or windings and you are getting not only the15,735 Hz horizontal (NTSC) but also various subharmonics of this. This improbably acceptable but may increase the temperature of the flyback. Using appropriate safety precautions, you can try prodding the varioussuspect parts (flyback, deflection yoke, other transformers) with aninsulated tool such as a dry wooden stick. Listen through a cardboardtube to try to localizing the source. If the sounds changes, youknow what part to go after. Sometimes a replacement flyback willcure the problem unless it is a design flaw. You do not want to replacethe yoke as convergence and other adjustments would need to be performed. Other transformers can be replaced. Note that the deflection frequency - just over 15 KHz for NTSC and PAL - ison 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!

REFERENCE :
http://www.stedmundsbury.gov.uk/sebc/play/tvprobs.cfm
http://www.epanorama.net/links/repair.html#tv