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From: kony on 29 Jan 2010 21:57
On Fri, 29 Jan 2010 03:27:26 +0100, "I.C. Koets"
<Nospam(a)please.com> wrote:

>My monitor (a DEC 21" CRT, older than dirt) has started to give sharp,
>static-discharge type audible ticks, which are accompanied by short
>distortions of picture and dimming. The picture distortion lasts for a
>refresh cycle, the dimming can take a few cycles to disappear.
>
>When I power off the screen, I hear a number of these ticks happening,
> one after the other, tapering off.
>
>Where do I begin to look for a solution? Google has not been much help.
>
>Thanks!


As others suggested it seems to be an arc in a high voltage
area. If it were newer, or LCD monitors much more
expensive, I might think repair a more viable option.
"Older than dirt" on the other hand, you have to look at
what lifespan it would have remaining if you fix this fault,
and the next one, and so on, and what you ultimately end up
with after all these repairs - an old heap that takes up
half the desk and costs quite a bit to use in electricity.

Maybe such monitors never should have been made, but one way
or the other eventually it will go to a landfill and/or be
recycled, and IMO, that time is now. Be glad that it lasted
so long, now you have the option of an LED backlit, LCD
display which will hopefully have a longer lifespan than the
predecessor LCDs with CCFL backlighting.
From: Strobe on 30 Jan 2010 07:13
On Thu, 28 Jan 2010 21:01:30 -0600, philo <philo(a)privacy.net> wrote:

>I.C. Koets wrote:
>> My monitor (a DEC 21" CRT, older than dirt) has started to give sharp,
>> static-discharge type audible ticks, which are accompanied by short
>> distortions of picture and dimming. The picture distortion lasts for a
>> refresh cycle, the dimming can take a few cycles to disappear.
>>
>> When I power off the screen, I hear a number of these ticks happening,
>> one after the other, tapering off.
>>
>> Where do I begin to look for a solution? Google has not been much help.
>>
>> Thanks!
>
>
>
>That's a hi-voltage breakdown
>
>
>My advice is not to fool with it as the high-voltage is dangerous.
>
>OK
>
>now that you've insisted to ignore caution
>you will need to open the monitor and observe where it's arcing
>{turning the lights off in the room will help}
>
>
>
>Now with the monitor off you can spray down the area with corona dope or
>other suitable insulation.
>
>
>NOTE: even with the power off and the unit unplugged...hi-voltage will
>be retained!!!!
>
>
>So you should not really fool with it

That's a big and heavy monitor.
For anyone who plans to flirt with death, I recommend placing it face down
on a firm cushion to remove the case screws.

Due to electrostatic cling, the high voltage parts may be encrusted with
airborne crud; simply cleaning this off may be enough.

And do not turn it on with the case off unless you're prepared to leave it
unplugged for a day before you go near it again.
When working on a radar display, I once got hit with 5 Kv - fortunately in one
finger and out my thumb, not through my chest - and it's not something I'd ever
like to repeat.

There's more than extra high voltage waiting to bite you.
That big tube - as well as being a big EHT capacitor - is also loaded with
vacuum. Sharp bits of glass can fly if it implodes.
Be VERY careful.
Don't work on that stuff alone - you want someone nearby able to dial 911.
From: John Corliss on 30 Jan 2010 07:51
larry moe 'n curly wrote:
> John Corliss wrote:
>>
>> CRTs, especially old ones, should be recycled at this point. They're not
>> worth trying to save when they go out.
>
> The best way to recycle electronics is by repairing it and keeping it
> in operation. Other recycling is a joke and dumps lots of hazardous
> waste into the environment, contrary to what the recycling industry
> would like us to believe otherwise.

Do you have any sources for your claims?

> Most monitor repairs are simple and cheap to people who know how to
> solder and operate a volt-ohm meter.

I disagree. Keeping a CRT in operation is like trying to keep accessing
the internet with a Pentium-90. Sure, you can do it, but the experience
sucks. Not only that, but you will eventually destroy your eyes after
years of putting up with the continual flickering, no matter how fast
the refresh rate, of a CRT monitor. I know this from personal experience.

>> Working on a CRT, as others in this thread have warned you, can get you
>> killed if you touch a high voltage capacitor for instance. Not only
>> that, but if you actually succeed in turning on a CRT with it's cover
>> off, you will be exposing yourself to dangerous radiation. Seriously.
>
> You're right about the shock hazard but are completely wrong about the
> radiation, unless you're referring to ancient color monitors
> containing high voltage rectifiers consisting of vacuum tubes rather
> than silicon diodes, and no way will the PLASTIC cover of a monitor
> (usually the only cover there is) provide any protection against
> radiation. Where did you get your gross misinformation about the
> radiation, and why do you believe it?

Some of the CRTs I've taken apart have shielding built into the plastic
cover along with a big warning on the back of the cover that this will
happen.

--
John Corliss
From: Paul on 30 Jan 2010 12:26
John Corliss wrote:
> larry moe 'n curly wrote:
>> John Corliss wrote:
>>>
>>> CRTs, especially old ones, should be recycled at this point. They're not
>>> worth trying to save when they go out.
>>
>> The best way to recycle electronics is by repairing it and keeping it
>> in operation. Other recycling is a joke and dumps lots of hazardous
>> waste into the environment, contrary to what the recycling industry
>> would like us to believe otherwise.
>
> Do you have any sources for your claims?

If you want to see the ugliness, check the Basel Network site.

http://www.ban.org/photogallery/index.html

Right now, as I speak, containers will be leaving the west coast
of Canada, destined for places like China or India. Even when
you deposit your electronics at a so-called "local recycler", there
is no guarantee they won't be loaded into a container and labeled
as "working electronics" headed to another country. With lax
enforcement, and not enough staff to search every container, they
can do what they want. (I believe that was highlighted on an
investigative journalism program on local TV here.)

Here is a beauty. Monitors stacked 4 meters high in Hong Kong.

http://www.ban.org/photogallery/china_guiyu_2008/pages/hongkong_smuggling_depot.html

These are places where your e-waste ends up.

http://www.greenpeace.org/raw/image_full/india/photosvideos/photos/map-of-asia-showing-where-e-wa.gif

There may be laws in place, but without enforcement, it is pretty
hard to stop it.

Paul
From: I.C. Koets on 1 Feb 2010 17:21
Thank you all for your contributions, I reply to this one because it
seems the most useful.

I am interested in repairing the old 30-kg machine because thus far I
have not seen a single LCD that gets close to it in picture quality
and motion representation. People say that LCD's have come a long way,
but they still don't match the performance of these old machines. I am
frankly surprised that people accept the image quality in exchange for
a bit of desk space.


larry moe 'n curly wrote:
>
> Try Googleing "monitor repair" because there's a lot of information
> about this, including from the great electronics repair FAQ:
>
> http://www.repairFAQ.org (especially read its safety information!)
>
Thanks, that (and the other links) looks useful. I will have a good
browse through it.

I do have a small amount of high voltage experience, and some
technical background, so I'm familiar with the dangers.

> #3: Glass breakage may be more a hazard than electric shock. CRT
> monitors have almost all their weight centered about 2" from the
> front of the screen, meaning they can easily fall forward, so don't
> set the monitor upright on a soft surface, like a bed. One person
> did that and his monitor fell to the floor and broke the glass, but
> fortunately the cabinet and the laminated safety shield on the
> front prevented any violent implosion/explosion from shooting out
> shards. If you work on the monitor, either place it on a hard,
> perfectly horizontal tabletop with a pillow in front to catch the
> monitor if it falls forward, or set the monitor face-down on some
> padding.
>
>
> #4: Do not unplug the big suction cup on the side of the CRT
> because that's a high voltage (30,000 volts) connection and retains
> high voltage forever (and even if you discharge it, the charge
> comes back). Actually the shock harzard from this isn't that bad,
> but when people get shocked they often jerk their hand, either
> voluntarily or involuntarily, and cut it up or hit the CRT and
> possibly break glass (see implosion/explosion warning above).

The 'suction cup', which does not appear to be sucked on, looks like
the prime suspect for the discharges - so far. I suspect the clamps
underneath it might be arcing to the Aquadag outside.

> #5: It's possible to get a shock of a few hundred volts from other
> parts of the monitor, such as some big capacitors in the main
> power supply and horizontal output section (also a power supply),
> but those capacitors almost always discharge to zero in a few
> seconds. If they don't, then the shock is probably more dangerous
> than the higher voltage one from the CRT.
>
> #6: There is NO radiation hazard, and anybody who says otherwise
> either thinks your monitor was made before 1972 or is a complete
> idiot.

Misinformed more than idiot. It's one of those popular truths that
does not stand up to scrutiny.


> The ticking sound may be from a short in a coil, such as the one
> around the neck of the CRT, and maybe it can be fixed by coating it
> with some oil-based varnish, after blowing it off with air or some
> electronic parts cleaner (auto parts stores, electronic supplies,
> Radio Shack -- get the stuff that does not leave an oily film, as
> tuner cleaner often does). Let any parts cleaner dry for a couple
> of hours, in a warm room, before varnishing. If the bad coil is
> the flyback transformer (the chunk of plastic with the thick cable
> going to that suction cup on the CRT), then you should probably
> junk the monitor, unless you just happen to have an identical
> monitor (same chassis; doesn't have to be same brand or model) with
> a completely different and expensive defect with it.
>
> Never overlook bad solder joints, which are often around heavy
> components (like that flyback transformer), hot components (big
> resistors, big transistors, or anything attached to a heatsink),
> and connectors. Those joints may be bluish or dull from heat, have
> hairline cracks (invisible except under magnification), or were
> bad from the beginning because their wire leads were dirty (each
> joint may look like a ball).
>
> Look for burn marks and dark areas on the circuit board. Resistors
> can turn brown or even crack open from heat. Electrolytic
> capacitors, which are aluminum cylinders covered with plastic
> shrink wrap, sometimes bulge or rupture on top or leak on top or
> bottom, but they can go bad without showing any physical signs.
>
> If you don't feel like repairing the monitor, at least try to give
> it to somebody who'll give it a try because most repairs aren't
> that difficult, and it would be a shame to waste something that may
> need just a simple, cheap fix. Out of 12-15 junked CRT monitors
> I've found on the sidewalk, I was able to repair all but one of
> them (a real stinker -- literally like burning plastic), and I'm no
> expert.

A good clean might be in order, but that's one of the riskier
operations. How long does it take for the capacitors to drain on their
own enough for safety?

The odd thing is that there are more discharges with the power off
than during operation. Is that a hint to look for any part?
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