Buzzing Toshiba

[MichaelJS]

I have a Toshiba model CX35F70 that is about 10 years old.

Recently when the picture contains light coloured elements there is a noticeable buzz coming from the TV, escalating in volume as the picture gets whiter. As this is winter in the snow belt of Canada I am getting lots of pictures featuring white.

It is greatly diminished or absent with darker scenes.

It persists even if the volume is reduced to minimum or muted.

I have been searching the 'net to determine what the problem may be to no avail.

One technician suggested it may be a loose shadow mask that vibrates when there is a high energy picture like a white background.

I want to know what may be happening so I can determine my next course of action. If it is a tube replacement is there enough value left in the TV absent Colour Stream inputs or is it now time to look to replace this unit?

Thank you for your assistance and guidance.

[red16v]

In laymans terms. As the crt is 'pushed' to show a high brightness picture so more current is demanded by the electrons beams landing on the front of the crt. In a well designed tv set this increase in current demand should be well provided for by the design of the tv. However as the tv ages so do the electronic components within it. As the components 'age' so they become 'tired' and less able to supply the current demanded by the bright pictures. Things inside like electronic 'coils' within the set become 'loosened up' and can actually vibrate - as the current through them increases so the amount of vibration can increase - to the extent sometimes that you can hear it buzzing. All this is quite normal as the tv ages (and 10 years is reasonabley old for a modern tv). The buzzing you can hear is being caused by the internal electronic components inside showing their age - that is why the volume of the noise is not affected by the volume control because it's the inside of the tv itself causing your problem. It is nothing to do with the shadow mask and there is nothing wrong with your crt (except of course that at 10 years old it will not be producing as brighter and clear picture as it did when it was new). You could spend a fair bit of cash having many internal components changed but it is definitely not worth it on a tv set of this age. Your simplest and cheapest solution in the long term is to buy a new tv set. Apologies if my explanation seems a little 'curt' but I did say it was in laymans terms. Regards, yt.

[MichaelJS]

Cheers for the response and thank you. I appreciate the layman's terms as well.

My research has lead to a possibly bad cap that can be replaced, is this a potential fix?

[Laurel&Hardy]

You could try it but don't be surprised if it doesn't work. The transformers and other wound components make the noise and it's probably the main switched mode transformer that's the culprit. As red says components do age and loosen up, especially inside a TV and this is part of the reason for the noise that you hear. It's concievable that a short or open circuit cap could cause the transformer to make this noise, but you would see many other side effects besides simply hearing the noise. One thing it definitely isn't is the shadow mask inside the CRT.

By all means try it though.

[red16v]

Hi, Yes I agree with 'L&H' it could be a lone capacitor. I repair tvs for a living (as well as many other things!) so if you want to try replacing the capacitor have a go but, as already pointed out don't be disappointed if it's not the cure. (BTW how did you decide it may be a particular capacitor ?) Regards, yt.

[MichaelJS]

VIa a Google.ca search I came accross this addy...

http://www.u-view-circuits.co.uk/upd...oshiba_92.html


from another UK site that suggested a cause and cure.

Cheers.