Another question for you experts here.

My daughter has a 20-year old Samsung 14" TV, model CI-338GA. Even after 
all this time it still produces a crisp picture, and isn't ready for 
scrapping yet.

But recently, after about 20 minutes from switch-on, the region around 
the LOPT has started to emit a very loud high-pitched screeching noise, 
making it impossible to continue viewing. When I switch off, remove the 
back cover, and switch on again, this doesn't happen -- it runs for 
hours without a peep. As soon as I replace the cover, the screeching 
returns after about 20 minutes.

At first I suspected that the cover, which is a tight fit, was somehow 
applying pressure to the printed circuit board and distorting it, but 
this isn't the case.

I even tried removing the cover when the screeching was in full swing, 
but the noise continued.

This is driving me nuts. Ideas anyone?

-- 
Ian

"Ian"  wrote in message 
news:pgSVKQJHZswIFw9U@ntlworld.com...
> Another question for you experts here.
>
> My daughter has a 20-year old Samsung 14" TV, model CI-338GA. Even after 
> all this time it still produces a crisp picture, and isn't ready for 
> scrapping yet.
>
> But recently, after about 20 minutes from switch-on, the region around the 
> LOPT has started to emit a very loud high-pitched screeching noise, making 
> it impossible to continue viewing. When I switch off, remove the back 
> cover, and switch on again, this doesn't happen -- it runs for hours 
> without a peep. As soon as I replace the cover, the screeching returns 
> after about 20 minutes.
>
> At first I suspected that the cover, which is a tight fit, was somehow 
> applying pressure to the printed circuit board and distorting it, but this 
> isn't the case.
>
> I even tried removing the cover when the screeching was in full swing, but 
> the noise continued.
>
> This is driving me nuts. Ideas anyone?

Common occurrence on many chassis, the LOPTX or other wound
components in the line output or PSU mechanically vibrating at
high AF
You are on the right lines, try to damp the vibration by lightly
touching each inductor with an insulated tool in order to identify
which one(s) are causing the whistle, then the options are to
either wrap cable ties around the ferrite core to hold the parts together
or use glue to damp them or both.
One consolation is that as you get older this won't be so much of
a problem, when I was young I could always hear the 15,625
from a 625 line set and 10,125 from a 405 set was almost painful.


-- 
Graham.

%Profound_observation%

"Graham."  wrote in message 
news:g9ujhd$4n5$1@registered.motzarella.org...
>
> "Ian"  wrote in message 
> news:pgSVKQJHZswIFw9U@ntlworld.com...
>> Another question for you experts here.
>>
>> My daughter has a 20-year old Samsung 14" TV, model CI-338GA. Even after 
>> all this time it still produces a crisp picture, and isn't ready for 
>> scrapping yet.
>>
>> But recently, after about 20 minutes from switch-on, the region around 
>> the LOPT has started to emit a very loud high-pitched screeching noise, 
>> making it impossible to continue viewing. When I switch off, remove the 
>> back cover, and switch on again, this doesn't happen -- it runs for hours 
>> without a peep. As soon as I replace the cover, the screeching returns 
>> after about 20 minutes.
>>
>> At first I suspected that the cover, which is a tight fit, was somehow 
>> applying pressure to the printed circuit board and distorting it, but 
>> this isn't the case.
>>
>> I even tried removing the cover when the screeching was in full swing, 
>> but the noise continued.
>>
>> This is driving me nuts. Ideas anyone?
>
> Common occurrence on many chassis, the LOPTX or other wound
> components in the line output or PSU mechanically vibrating at
> high AF
> You are on the right lines, try to damp the vibration by lightly
> touching each inductor with an insulated tool in order to identify
> which one(s) are causing the whistle, then the options are to
> either wrap cable ties around the ferrite core to hold the parts together
> or use glue to damp them or both.
> One consolation is that as you get older this won't be so much of
> a problem, when I was young I could always hear the 15,625
> from a 625 line set and 10,125 from a 405 set was almost painful.
>
>
> -- 
> Graham.
>
> %Profound_observation%

we had the same problem with I Philips TV almost from new, the engineer came 
out (still in warranty) and rubbed some Vaseline on it, that cured it 
instantly,
he said it was because it was hot and dry and a bit of lube will sort it 
out, it has been perfect for the last 5 years.


-- 
The Glory Hornet

"TGH" <what@no.invalid> wrote in message 
news:6ig83nFqje72U1@mid.individual.net...
>
>
> "Graham."  wrote in message 
> news:g9ujhd$4n5$1@registered.motzarella.org...
>>
>> "Ian"  wrote in message 
>> news:pgSVKQJHZswIFw9U@ntlworld.com...
>>> Another question for you experts here.
>>>
>>> My daughter has a 20-year old Samsung 14" TV, model CI-338GA. Even after 
>>> all this time it still produces a crisp picture, and isn't ready for 
>>> scrapping yet.
>>>
>>> But recently, after about 20 minutes from switch-on, the region around 
>>> the LOPT has started to emit a very loud high-pitched screeching noise, 
>>> making it impossible to continue viewing. When I switch off, remove the 
>>> back cover, and switch on again, this doesn't happen -- it runs for 
>>> hours without a peep. As soon as I replace the cover, the screeching 
>>> returns after about 20 minutes.
>>>
>>> At first I suspected that the cover, which is a tight fit, was somehow 
>>> applying pressure to the printed circuit board and distorting it, but 
>>> this isn't the case.
>>>
>>> I even tried removing the cover when the screeching was in full swing, 
>>> but the noise continued.
>>>
>>> This is driving me nuts. Ideas anyone?
>>
>> Common occurrence on many chassis, the LOPTX or other wound
>> components in the line output or PSU mechanically vibrating at
>> high AF
>> You are on the right lines, try to damp the vibration by lightly
>> touching each inductor with an insulated tool in order to identify
>> which one(s) are causing the whistle, then the options are to
>> either wrap cable ties around the ferrite core to hold the parts together
>> or use glue to damp them or both.
>> One consolation is that as you get older this won't be so much of
>> a problem, when I was young I could always hear the 15,625
>> from a 625 line set and 10,125 from a 405 set was almost painful.
>>
>>
>> -- 
>> Graham.
>>
>> %Profound_observation%
>
> we had the same problem with I Philips TV almost from new, the engineer 
> came out (still in warranty) and rubbed some Vaseline on it, that cured it 
> instantly,
> he said it was because it was hot and dry and a bit of lube will sort it 
> out, it has been perfect for the last 5 years.
>
>

That sounds to me like he used silicone grease to address a different
problem, that of a hissing sound caused by the 25KV or more EHT
"brushing". The only thing is, that it is cold damp condition that usually
cause this.


-- 
Graham.

%Profound_observation%

Can't help with the OP's problem, but I'm reminded of an old joke ...

Did you hear about the Irish couple who didn't know the difference
between Vaseline and putty?

Terrible business!

All their windows fell out!

On Sat, 6 Sep 2008 21:39:28 +0100, "TGH" <what@no.invalid> wrote:
> 
> the engineer came 
> out (still in warranty) and rubbed some Vaseline on it

Well, its obviously something which resonates at, a frequency  related to 
the  scanning frequency, say half or maybe less, excited by the  powerful 
oscillations.

Unfortunately, these sort of problems , especially in such a dangerous area 
to poke about in while its running are impossible to find sometimes. I can 
recall one such  noise on an old Decca set  was fixed by wedging a piece of 
carefully whittled polystyrene under the centre of the pcb and the case. 
Probably not good for the fire hazard side of things though.

I'm loathe to suggest  using epoxy on the wound components in case it is 
going to make it worse I would say though the 20 years is good, and maybe 
its time for a change?
Brian

-- 
Brian Gaff....Note, this account does not accept Bcc: email.
 graphics are great, but the blind can't hear them
Email: briang1@blueyonder.co.uk
______________________________________________________________________________________________________________


"Ian"  wrote in message 
news:pgSVKQJHZswIFw9U@ntlworld.com...
> Another question for you experts here.
>
> My daughter has a 20-year old Samsung 14" TV, model CI-338GA. Even after 
> all this time it still produces a crisp picture, and isn't ready for 
> scrapping yet.
>
> But recently, after about 20 minutes from switch-on, the region around the 
> LOPT has started to emit a very loud high-pitched screeching noise, making 
> it impossible to continue viewing. When I switch off, remove the back 
> cover, and switch on again, this doesn't happen -- it runs for hours 
> without a peep. As soon as I replace the cover, the screeching returns 
> after about 20 minutes.
>
> At first I suspected that the cover, which is a tight fit, was somehow 
> applying pressure to the printed circuit board and distorting it, but this 
> isn't the case.
>
> I even tried removing the cover when the screeching was in full swing, but 
> the noise continued.
>
> This is driving me nuts. Ideas anyone?
>
> -- 
> Ian

"Brian Gaff"  wrote in message 
news:%8Lwk.54282$E41.27852@text.news.virginmedia.com...
> Well, its obviously something which resonates at, a frequency  related to 
> the  scanning frequency, say half or maybe less, excited by the  powerful 
> oscillations.
>
> Unfortunately, these sort of problems , especially in such a dangerous 
> area to poke about in while its running are impossible to find sometimes. 
> I can recall one such  noise on an old Decca set  was fixed by wedging a 
> piece of carefully whittled polystyrene under the centre of the pcb and 
> the case. Probably not good for the fire hazard side of things though.
>
> I'm loathe to suggest  using epoxy on the wound components in case it is 
> going to make it worse I would say though the 20 years is good, and maybe 
> its time for a change?
> Brian


When I was in the TV trade we used to use great dollops
of the Radiospares equivalent of Evo-Stick.
Come to think of it, I wonder how inflammable that stuff was
when cured?
-- 
Graham.

%Profound_observation%

Graham. wrote:
> "Ian"  wrote in message 
> news:pgSVKQJHZswIFw9U@ntlworld.com...
>> Another question for you experts here.
>>
>> My daughter has a 20-year old Samsung 14" TV, model CI-338GA. Even after 
>> all this time it still produces a crisp picture, and isn't ready for 
>> scrapping yet.
>>
>> But recently, after about 20 minutes from switch-on, the region around the 
>> LOPT has started to emit a very loud high-pitched screeching noise, making 
>> it impossible to continue viewing. When I switch off, remove the back 
>> cover, and switch on again, this doesn't happen -- it runs for hours 
>> without a peep. As soon as I replace the cover, the screeching returns 
>> after about 20 minutes.
>>
>> At first I suspected that the cover, which is a tight fit, was somehow 
>> applying pressure to the printed circuit board and distorting it, but this 
>> isn't the case.
>>
>> I even tried removing the cover when the screeching was in full swing, but 
>> the noise continued.
>>
>> This is driving me nuts. Ideas anyone?
> 
> Common occurrence on many chassis, the LOPTX or other wound
> components in the line output or PSU mechanically vibrating at
> high AF
> You are on the right lines, try to damp the vibration by lightly
> touching each inductor with an insulated tool in order to identify
> which one(s) are causing the whistle, then the options are to
> either wrap cable ties around the ferrite core to hold the parts together
> or use glue to damp them or both.
> 

It will be much easier to deal with the problem if you can find out 
exactly where the noise is coming from before you start. Obviously, this 
is an area where extremely high and dangerous voltages abound, so this 
needs to be done in a safe manner.

You will need an insulated tube (a sheet of A4 paper rolled up and held 
with tape or rubber bands is fine.) If the chassis is particularly deep, 
you may need a longer tube - use 2 sheets of paper!

If necessary, move the TV so that you have completely free access to the 
  chassis. Wait for the noise to start, then remove the cover.

With the tube to your ear, and keeping your hand as far up the tube as 
possible, use the other end as a stethoscope, moving it around to find 
out exactly where the noise is coming from (this technique can produce 
extremely accurate results if you keep the far end of the tube close to 
the components.)

The beauty of using a paper tube, rather than a piece of plastic waste 
pipe, or similar, is that you can push it against the problem area, when 
you find it, with no fear of causing physical damage. You can then use 
your eyes to see what you've found.

Incidentally, your description of what happens with and without the 
cover points to a temperature related problem of some kind.

Terry

Transformer T402 is the listed suspect. It may be that no amount of
wedging will solve the problem but it is always worth a try.
Failing electrolytic caps around the PSU and line stages can also be a
cause of this sort of thing

"TGH" <what@no.invalid> wrote in message 
news:6ig83nFqje72U1@mid.individual.net...
> we had the same problem with I Philips TV almost from new, the engineer 
> came out (still in warranty) and rubbed some Vaseline on it, that cured it 
> instantly,
> he said it was because it was hot and dry and a bit of lube will sort it 
> out, it has been perfect for the last 5 years.

Rubbing flammable petroleum jelly on the anything inside a television would 
be highly dangerous.
It must have been something else he used.

-- 

Brian Gregory. (In the UK)
ng@bgdsv.co.uk
To email me remove the letter vee.

"Brian Gregory [UK]"  wrote in message 
news:GfidnU_GGoQpclbVnZ2dnUVZ8sGdnZ2d@pipex.net...
> "TGH" <what@no.invalid> wrote in message 
> news:6ig83nFqje72U1@mid.individual.net...
>> we had the same problem with I Philips TV almost from new, the engineer 
>> came out (still in warranty) and rubbed some Vaseline on it, that cured 
>> it instantly,
>> he said it was because it was hot and dry and a bit of lube will sort it 
>> out, it has been perfect for the last 5 years.
>
> Rubbing flammable petroleum jelly on the anything inside a television 
> would be highly dangerous.
> It must have been something else he used.
> Brian Gregory. (In the UK)
>
>
KY Jelly?

Steve Terry

"Steve Terry"  wrote in message 
news:gahgm7$gl3$1@news.albasani.net...
> "Brian Gregory [UK]"  wrote in message 
> news:GfidnU_GGoQpclbVnZ2dnUVZ8sGdnZ2d@pipex.net...
>> "TGH" <what@no.invalid> wrote in message 
>> news:6ig83nFqje72U1@mid.individual.net...
>>> we had the same problem with I Philips TV almost from new, the engineer 
>>> came out (still in warranty) and rubbed some Vaseline on it, that cured 
>>> it instantly,
>>> he said it was because it was hot and dry and a bit of lube will sort it 
>>> out, it has been perfect for the last 5 years.
>>
>> Rubbing flammable petroleum jelly on the anything inside a television 
>> would be highly dangerous.
>> It must have been something else he used.
>> Brian Gregory. (In the UK)
>>
>>
> KY Jelly?

On the EHT nipple?


-- 
Graham.

%Profound_observation%

>>> Rubbing flammable petroleum jelly on the anything inside a television 
>>> would be highly dangerous.
>>> It must have been something else he used.
>>> Brian Gregory. (In the UK)
>>>
>>>
>> KY Jelly?
>
>On the EHT nipple?

TVs don't have knobs anymore?

-- 
Jimjonbobillyjo

From: Ian 
Date: Sat, 6 Sep 2008   Time: 19:04:55

>Another question for you experts here.
>
>My daughter has a 20-year old Samsung 14" TV, model CI-338GA. Even 
>after all this time it still produces a crisp picture, and isn't ready 
>for scrapping yet.
>
>But recently, after about 20 minutes from switch-on, the region around 
>the LOPT has started to emit a very loud high-pitched screeching noise, 
>making it impossible to continue viewing.

Thanks to everyone for the helpful hints on what to do to kill the 
screech. I thought about using Vaseline, but then decided this may be a 
bit risky. I have now finally made it to Maplins to get some silicone 
grease PTFE, sprayed it liberally around the whole of the EHT area, and 
bingo! Success! Looks like the TV is good for another 20 years.
-- 
Ian