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'[EE] Reparing my CRT monitor'
2008\07\20@090041 by Dennis Crawley

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Hi,

I have a few problems with my 12 years old monitor.

There is a noise of about 15Khz. When I drop down the resolution to 800x600
the noise stops.
As well as 1 hour after switched on.

Brigth is at maximum,
Kellyx JD144C-NON INTERLACED - 14"

I will apreciate some links or forums.

Regards,
Dennis


2008\07\20@095021 by Herbert Graf

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On Sun, 2008-07-20 at 10:02 -0300, Dennis Crawley wrote:
> Hi,
>
> I have a few problems with my 12 years old monitor.
>
> There is a noise of about 15Khz. When I drop down the resolution to 800x600
> the noise stops.
> As well as 1 hour after switched on.
>
> Brigth is at maximum,
> Kellyx JD144C-NON INTERLACED - 14"
>
> I will apreciate some links or forums.

Well, one solution is to wait until your ears can't hear 15kHz
anymore... :)

Unfortunately this sort of thing can be a little tricky to find. Usually
it's the result of a winding getting it's self loose someone. It could
also be a coil coming loose from it's physical mounting point.

Best course of action would be to see if you can isolate the component
the noise is coming from, then it's just a matter of replacing it,
although repairing it could also be an option.

TTYL

2008\07\20@101841 by Dave Lagzdin

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2008/7/20 Dennis Crawley <spam_OUTdennis.crawleyTakeThisOuTspamusa.net>:

> Hi,
>
> I have a few problems with my 12 years old monitor.
>
> There is a noise of about 15Khz. When I drop down the resolution to 800x600
> the noise stops.
> As well as 1 hour after switched on.
>

So if you shoot some cold spray on the warm offending component it might
stop?

I could suggest the old auto mechanics trick of pressing a wooden stick
against the suspect device and the other
end against his ear but I'm not sure how 15Khz propagates thru a stick, and
envision some "Einstein" with a fresh wet twig betwixt the flyback and his
ear- nevermind :)...
D


,

2008\07\20@120535 by Herbert Graf

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On Sun, 2008-07-20 at 10:18 -0400, Dave Lagzdin wrote:
> 2008/7/20 Dennis Crawley <.....dennis.crawleyKILLspamspam@spam@usa.net>:
>
> > Hi,
> >
> > I have a few problems with my 12 years old monitor.
> >
> > There is a noise of about 15Khz. When I drop down the resolution to
> 800x600
> > the noise stops.
> > As well as 1 hour after switched on.
> >
>
> So if you shoot some cold spray on the warm offending component it
> might
> stop?

That might very well work, didn't think of that. Couldn't hurt trying.

> I could suggest the old auto mechanics trick of pressing a wooden
> stick
> against the suspect device and the other
> end against his ear but I'm not sure how 15Khz propagates thru a
> stick, and
> envision some "Einstein" with a fresh wet twig betwixt the flyback and
> his
> ear- nevermind :)...

Ya, I have my doubts that wood would work well, that said, something
harder might work. I'd suggest a metal rod, but the conductive side has
issues there. Perhaps a glass rod?

TTYL

2008\07\20@121944 by John Coppens

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On Sun, 20 Jul 2008 10:02:56 -0300
"Dennis Crawley" <dennis.crawleyspamKILLspamusa.net> wrote:

> There is a noise of about 15Khz. When I drop down the resolution to
> 800x600 the noise stops.
> As well as 1 hour after switched on.

I don't know if it has ever been done, but a good first step is clean the
monitor inside (use pressured air if you have a compressor). Sometimes,
dust provides a discharge path for the high voltage (though mostly it
manifests itself on the screen then).

If the noise really comes from the high voltage circuit, it could be an
indication that the flyback transformer is about to give up. And near
that transformer, there are a couple of capacitors that I've known to
start generating noise.

Judging from the age, I don't think the power supply is switched, so that
shouldn't be the source.

John

2008\07\20@133927 by Richard Seriani, Sr.

picon face

----- Original Message -----
From: "John Coppens" <.....johnKILLspamspam.....jcoppens.com>
To: "Microcontroller discussion list - Public." <EraseMEpiclistspam_OUTspamTakeThisOuTmit.edu>
Sent: Sunday, July 20, 2008 12:19 PM
Subject: Re: [EE] Reparing my CRT monitor


{Quote hidden}

**
High voltage discharge will not manifest itself as a 15kHz noise. Instead,
it will be an arcing, snap, or sizzle.

Using compressed air from an air compressor is normally NOT a good idea.
Unless you regulate the pressure down to a rather low level, you take the
chance of causing damage to some of the very flimsy boards/connectors used
in many monitors.
More importantly, some compressors discharge a small amout of oil with the
air. This will create an environment where the buildup of dust will increase
drastically causing, among other problems, excessive heat buildup.
If you must blow the dust out (seldom an issue unless used in a dirty
environment), use a can of clean compressed air or an attachment on your
vacuum cleaner hose, with the hose attached the discharge side of the vacuum
cleaner (DO NOT try to suck the dust out!). If you must try brushing extreme
buildup, do so VERY gently with a soft brush (like a makeup brush), to
avaoid damage.
**

> If the noise really comes from the high voltage circuit, it could be an
> indication that the flyback transformer is about to give up. And near
> that transformer, there are a couple of capacitors that I've known to
> start generating noise.
>
**
>From your stement that changing resolution makes the sound come and go, it
makes sense that the problem is in the horizontal frequency
generation/horizontal deflection section. Afer all, one of the things that
changes with different resolutions is the horizontal scanning frequency.

Check around the horizontal output section for one or more small iron-core
coils. These are notorious for having loose cores. Pressing on the coil with
a non-conductive tool may make the offending sound go away. If so,
replacement may not be an option (monitor parts are sometimes difficult to
come by, as well as generally expensive), but you can desolder it and apply
a bit of RTV or hot glue (use a type that cools to a soft consistency) to
the base of the coil (where the core is usually inserted). Sometimes, this
will do the trick.
**

Good luck,
Richard

> Judging from the age, I don't think the power supply is switched, so that
> shouldn't be the source.
**
Even if this unit uses an SMPS (and they were in wide use in 1996), there
would have to be a short, or near short, to cause the frequency to get low
enough to be audible by humans, so, that is not likely to be the source of
the noise.
**
>
> John
> --


2008\07\20@155824 by olin piclist

face picon face
Dennis Crawley wrote:
> I have a few problems with my 12 years old monitor.
> ...
> Brigth is at maximum,
> ... 14"

Get a new one.  That old dinosaur isn't worth bothering with.  14" was
pretty small even in 1996.  You'll find monitors are a lot cheaper now 12
years later.  Trying to fix one is a waste, especially since your cathode
coating has worn out.  You can probably replace it with a 19" LCD for what
you paid for the klunker back then.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\20@171025 by Apptech

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> There is a noise of about 15Khz. When I drop down the
> resolution to 800x600
> the noise stops.
> As well as 1 hour after switched on.
>
> Brigth is at maximum,

Just as a possible add on to the other suggestions.
Most CRT HV units have a non user-adjustable focus
adjustment knob on them and some have two knobs with the
second altering brightness by altering voltage.

In old monitors, adjusting the focus control is usually
beneficial. Adjusting the brightness control to bring the
usual adjustment pot back from its maximum position and/or
give you more brightness is also often useful.

it *MAY* be that, if the latter option is available in your
case, that it will also affect the sound output that you
mention, as eg the load offered by the pot may be reduced.
May well not help but arguably worth trying.

In situations where the above help the monitor is usually
well on its way to dying and these are stop-gap measures
which may give it slightly more life.



       Russell


2008\07\20@171822 by Dennis Crawley

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Thanks for the inputs, gentlemen.
I'll give a chance to this dinosaur, just because I don't need a new one.
How can we disposal the old electronics with out polluting?... but this
would be a [TECH] subject.

I'll make some comments as soon as I have some time to work on it this week.

Best regards for all
Dennis.



2008\07\20@185731 by Tamas Rudnai

face picon face
> How can we disposal the old electronics with out polluting?... but this
> would be a [TECH] subject.

It depends who is 'we' I guess. Myself removing all usable components for
home projects (LCDs from calcs, big bold FETs from mother boards etc) then
the rest goes to the recycle area where they collect electronic waste. What
'they' do it with I have no idea, so I do not know what 'we', humans doing
with those to be honest.

Tamas



On Sun, Jul 20, 2008 at 10:08 PM, Dennis Crawley <@spam@dennis.crawleyKILLspamspamusa.net>
wrote:

{Quote hidden}

> -

2008\07\20@191614 by Apptech

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>> How can we disposal the old electronics with out
>> polluting?... but this
>> would be a [TECH] subject.

Previously much electronic equipment here was compacted
somewhat and shipped to, I think, China. I was told more
recently that that market was no longer economic.



       Russell


2008\07\20@192017 by Jinx

face picon face
> How can we disposal the old electronics with out polluting?... but this
> would be a [TECH] subject.

Dennis, I do what Tamas does - strip appliances for anything useable
or interesting and pile the remainder. I think this still does just qualify
for [EE] as a lot of us are dumpster divers and would like to get rid of
waste responsibly (or at least think about it)

This company has been advertising on NZ radio lately

http://www.rcn.co.nz/ewaste.php

"RCN Envirocare certifies that all electronic scrap it receives
is handled in a manner compliant with environmental standards.
RCN's reporting provides a complete audit trail"

Is there a company or scheme like that near you ?

2008\07\20@203407 by Carl Denk

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Here in Lorain County, northern Ohio, USA, the county has regular
collections where you bring the pieces to a central location. Then items
are picked up (several truck loads twice a year), taken to a contractor
in Cleveland who pieces together computers (several hundred were
returned to local schools and government last year), sends other items
to recyclers that reclaim the metals and parts. TV CRT tubes are sent to
South America (Argentina I think?) where new electron guns are installed
and the tubes become replacements and possibly installed in new sets. It
is guaranteed that noting is landfilled.

Jinx wrote:
{Quote hidden}

2008\07\20@204058 by Carl Denk

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The China recycling is really bad! The items are stripped in really poor
conditions by humans of all ages. Items that need to be burned to get at
the metals are burnt in open fires, with offensive (dangerous) fumes
spreading for miles. Last week there was a program on the Current
channel (Directv channel 366) showing the conditions, it was really bad,
and small children were there inhaling the fumes.

Apptech wrote:
{Quote hidden}

2008\07\20@213504 by Jinx

face picon face
> The China recycling is really bad !

That's certainly a recommendation for searching out a recycler
who does make some effort to recover materials without just
transferring the pollution to another part of the world. Even if
waste ended up in a controlled or secure landfill (possibly)

2008\07\20@215455 by Apptech

face
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> The China recycling is really bad! The items are stripped
> in really poor
> conditions by humans of all ages. Items that need to be
> burned to get at
> the metals are burnt in open fires, with offensive
> (dangerous) fumes
> spreading for miles. Last week there was a program on the
> Current
> channel (Directv channel 366) showing the conditions, it
> was really bad,
> and small children were there inhaling the fumes.

Consistent with what bob Blick was reporting a while ago in
other '3rd world' recycling schemes.

I've seen photos of African lead acid battery recycling
furnaces and processing plants and they are horrendously
fearsome. I would literally not want to come within hundreds
of metres of one when it was operating.


           Russell



2008\07\20@222516 by Carl Denk

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All those ocean containers going one direction with goods, return with
stuff for this type recycling, and then the seafood that is harvested
from downstream from the recycling operations. I just learned of an
aquaculture operation raising shrimp in Northern Ohio. They are raised
in clean fresh water.

Jinx wrote:
>> The China recycling is really bad !
>>    
>
> That's certainly a recommendation for searching out a recycler
> who does make some effort to recover materials without just
> transferring the pollution to another part of the world. Even if
> waste ended up in a controlled or secure landfill (possibly)
>
>  

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