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Very loud 'Buzz' when picture is lighter on TV


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Old 03-10-2009, 09:43
jonparadise
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We just moved house, and moved our Freeview Receiver/HD TV setup with us.

Unfortunately we had virtually no TV at all for the first couple of weeks as the signal was too poor. We called a man out and the areal connection was duff, so it's now really strong.

Now we have another problem!

The picture is now perfect, but whenever the picture is 'lighter' in colour and especially when a lot of white is displayed, there is a very loud buzz.

Any idea what could be causing this?

If it makes any difference, if we connect the signal to the TV internal Freeview receiver, there is no noise at all.
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Old 03-10-2009, 09:48
jono t
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Sounds like you have a duff scart lead to your settop box, change the scart and see if this is the problem.
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Old 03-10-2009, 11:10
platelet
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If you try googling "sync buzz" you'll find a lot on it.

how are you connecting the external tuner to the tv (scart, hdmi, rf)?
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Old 03-10-2009, 16:05
John Currie
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The OP stated "if we connect the signal to the TV internal Freeview receiver"
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Old 03-10-2009, 17:38
chrisjr
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Can we just clarify something here. If I am reading this right then this is your set up

1/ You have a TV with built in Freeview
2/ You have an external box of some kind also with Freeview
3/ You have the box connected via a SCART lead to the TV
4/ You have the aerial plugged into the external box
5/ You don't have any aerial connection to the TV

If you watch Freeview via the external box you get a buzz on white pictures. If you plug the aerial into the telly no buzz. Right so far?

OK two very simple solutions.

1/ Buy a better fully screened SCART lead
2/ Buy an aerial lead to go from the RF/Aerial/Antenna OUT (whatever it is called) on the external box to the aerial in on the TV. Use the TV to watch Freeview most of the time and the box for recording (I assume it's a recorder as why else use it if the telly does Freeview?).

The noise is caused by unscreened cables in the SCART lead. It is the video signal flowing up one set of wires causing interference into the audio wires. A proper fully screened cable prevents this by having individual screens round each wire which in effect blocks signals from one wire getting into the wires around it.

The alternative may be that a screen has detached it self from the pin in the SCART plug and is no longer working as a screen. Either way a new lead will sort it. Just don't let the likes of Comet or Currys rip you off by selling you some 100 quid gold plated rubbish that earns then 99quid profit! You can get a perfectly good lead for 10 to 20 quid absolute top.
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Old 04-10-2009, 22:52
John Robinson
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This is interesting. It reminds me of our having the same problem many years ago, but with a stand-alone TV - no scart cables.

Could that have been down to something else?
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Old 04-10-2009, 23:18
chrisjr
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This is interesting. It reminds me of our having the same problem many years ago, but with a stand-alone TV - no scart cables.

Could that have been down to something else?
Poor design in the telly probably.

The noise was probably caused by the video circuits generating all kinds of spurious signals that got into the audio circuits. Either by some component radiating garbage through the air to another component (transformers are prime suspects for this). Or by the video circuits introducing crap onto the power supply which finds it's way into the audio stage.
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Old 05-10-2009, 09:30
Chris Frost
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This is interesting. It reminds me of our having the same problem many years ago, but with a stand-alone TV - no scart cables.

Could that have been down to something else?
If it was a CRT TV then it was probably coming from the electronics that drive the tube.

Almost all CRT TVs suffered from image shrink as the picture gets brighter. This is because of poor regulation of the power supply - it just can't keep with the demand for power when the picture contained a lot of light colours and the contrast was set high. Turning down the contrast control helps.
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Old 05-10-2009, 17:23
CheekyTV
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I had this buzzin noise on an old CRT TV a few years ago..had a TV repair man come out to have a look he said that it could be a copper coil that has come lose and that there isn't much you can do about it because it molded to a circuit board..etc...when he took the back off the TV he showed me what he meant...he got his pen out and put it on this copper looking coil and the noise stopped...took the pen away and the buzzin came back..had a new flat screen to replace it..no buzzin now although some flat screen buzz even more than CRTs..Acoustic Solutions LCDs are terrible for it..it is deffinately associated to the backlight I dont think they have it right somehow!..lol
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Old 05-10-2009, 21:45
John Robinson
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Thanks, chrisjr and Chris Frost.
Very enlightening.
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Old 06-10-2009, 13:23
jackthom
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This is interesting. It reminds me of our having the same problem many years ago, but with a stand-alone TV - no scart cables.

Could that have been down to something else?
Many old sets used to suffer from "intercarrier buzz" due to a sort of crosstalk between the vision and sound circuits.

This was often worse on a white screen when vertical syncs were more likely to break through onto the FM audio carrier.

Mistuning and drifting on sets without AFC produced similar problems.

The things we used to put up with in the past. I still remember when the majority of black and white sets had no DC restoration and the screen never went to black, just a murky grey on night shots.

Apologies for rambling on a bit.
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