Any value in cleaning inside old monitor?

Inside the circuit board was quite dusty and rather sooty. The
CRT tube and anything neary was very sooty.

----> Is there any merit in cleaning (hoovering or gently wiping)
this dirt? <----

MY THINKING: I figured that the reason why the soot was attracted
to the CRT tube was because the high voltage attracted the soot on
account of the hold being able to hold a charge (or maybe because
the soot was conductive or something like that).

Then I thought maybe the soot was allowing some of the high
voltage on the tube to leak away and that way reduce the picture
quality.

As you can see I have no real idea at all about the facts of this,
so I'm asking you specialists.

Sam

PS: I did clean the inside and I reckon picture looks a bit
sharper. But maybe I am completely deluding myself! Or maybe I
leant on one of the sharpness controls while I was cleaning!

At the voltages that can be running around in the back of a crt,
cleaning out accumulated "crud" is a damn good idea, since, as you say,
some of it may well be (semi)conductive.

Even if it's inert, it'll have a negative impact 'cause it's acting as a
blanket, keeping components hotter than they would be if running in
"free air" conditions.

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Just make sure you know where the high-voltage connector is, and how
to discharge it, these things can hold a lethal charge long after you
unplug them... IIRC you want to clean around the high-voltage power
supply, lead, and tube connector with isopropyl.

If you have a source of compressed air, it's a good idea to blow out
all the dust (outdoors, of course). That way, you will get all the
dirt in the nooks and crannies.

Beachcomber

I've always used a vaccum cleaner with the hose on the exhaust side
with the crevice tool attached. I even restrict the air output with my
hand or finger over the port to get more air velocity.

Good response! Keep hands away though! Make sure to use a long
handled feather duster as well as compressed air.

It doesn't need to be discharged if he leaves the damned connector
alone, aside from cleaning it off with air or a duster! It is best NOT
to discharge it. The connector is usually well sealed, and one
doesn't want to break that seal. Also, the flyback current limit
resistor can be damaged, though should be designed well enough to take
it.

Unplugging the AC line cord is one thing, but there is no need to
unplug an anode wire that is not already leaking!

He can merely use a duster brush, and compressed air for the entire
job. The goal is to reduce leakage form corona and reduce heat from
dust blanketing. No need to douse the damned OLD thing with a
solvent!

Which is typically really all that is needed.

Probably true, but if it's as grubby inside as the OP indicated, he
might have some (cooking) grease fallout in there, and might want to
properly clean around the HV parts, using care not to zap himself...

Try the dust removal thing first.

A high voltage shock from a CRT will definitely get your attention but
"lethal?" Only if your reaction the the shock causes you to fall out the
window or come into contact with something that's REALLY potentially lethal:
the line cord.

That's not to say that you don't take precautions. Getting a shock when
working on electronics is proof you haven't been as careful as you should
have been.

I tried to post much the same point but it didn't appear. The most dangerous
area of a TV or monitor is the mains smoothing capacitor, which is indeed
potentially lethal. I have never heard of a fatality from the CRT anode, and
it shouldn't be particularly hazardous to a healthy heart. The biggest
danger from the CRT anode is, as you say, secondary injury caused by reflex
action from the shock.

Dave

I wouldn't use any solvent, some solvents will disolve the aquadag (graphite
coating) off the back of the tube and you don't want that dripping all over
the EHT circuits. Better just blow the loose dust out, and maybe give it a
light and careful brushing (with a plastic handled brush if you're afraid
of the EHT).

Chris

Not only does it have the chance of getting onto circuitry, it also
changes the capacitance of the tube wall, changing the circuit for the
CRT drive elements as well.

Isopropyl will strip that stuff off? Who'da thunk it?

I think so, at least on some brands of tube. Can't remember for sure what
solvent I was using but I think it was isopropanol. It was a scrap set
anyway so I didn't mind too much.

Chris

One minor worry with compressed air if it comes from a compressor (as
opposed to a compressed air can) is condensation in the air hose, the water
droplets can be forced under components where they take a while to dry out!
If the air line doesn't have a condensation filter - blast it out for a few
seconds before pointing it inside the equipment.

Sound advice.

Thank you all for your advice.

All this now makes me think that my TV (which uses a 19 inch glass
tube) would also show an improved oicture if it too had the dust
cleaned out of it.

Is this correct? Or does a TV differ in some way from a PC monitor
when it comes to getting visible improvements from dusting?

Let's take a survey.... How many of the professional techs, engineers,
and scientists who read this group actually do periodic cleaning of inside
of their monitors and TVs?

If you're obsessive-compulsive and have nothing better to do, by all
means clean the insides of your CRT equipment. But it's probably more
likely that something will get messed accidentally, than any significant
improvement in either performance or life span.

The high voltage area of modern CRT equipment is generally enclosed and
or sealed with HV grease or adhesive. It's not like old all-tube-type
TVs where everything collected an inch of dust if you turned your back. :)

Yes, dust does collect. And yes in principle that may affect something
eventually. But if there are no symptoms, leave it alone. It's not
likely that a gradually degradation in performance is dust related.
My approach about these things is that "if it ain't broke, don't
fix it". :) Seriously, if you're in a dusty dirty shop floor, then
there may be some benefit. But if it's a home or office environment,
don't you have better things to worry about than to clean the insides
of your 34,153 electronic gadgets????

For the record, I do not clean inside electronic equipment unless there is
a reason to go inside. My TV is 26 years old and I've repaired it twice
over that span due to defective chokes (probably a parts problem from the
supplier at the time of manufacture). Other TVs in the house are all more
than 15 years old and except one set of cracked solder joints, havne't
needed repair since I acquired them. I generally keep computer monitors
for 8 or 10 years without problems.

Let the flame wars begin... NOW! ;-)

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Nope.

Neither will show a better picture by cleaning them out, it's nonsense!
Cleaning the optics in a RPTV may cure image issues if dust has worked its
way onto the mirror etc, but a direct view monitor or TV will be unaffected.

Dave

<snip>

No war from me, I agree totally!

Dave

Have you actually cleaned inside one of your monitors/TV in order to
see how noticeable (or not) the change in picture quality is?

It might be wrong to dismiss cleaning if you haven't seen the
benefits on your own CRTs. Once you have tried then you could say it
is or is not worth the effort.

I've cleaned a lot of them, but never for the sole
purpose of seeing if it affects picture quality.
It does not. But there is the possibility of
damaging something. If there is some other reason for
opening the monitor up, and if you are careful, you
might as well clean it while you are there.

Unless your monitor is in a "hostile" environment where
it can pick up a LOT of dust/lint/dirt/whatever, leave
the damn cover on it and clean the outside only. In a normal
residential setting, the best you can hope for is that you do
not damage the monitor/TV in the process.

Ed

Sure it does. The collection of dust, and much of that moistened at
some point makes for a leaky anode supply and feed wire at the very
least. That makes for poor or shifted focus settings, and other
problems that less than your average video afficianado won't notice.

Tis better to blow the stuff off with an air compressor. That's what I did
as a TV bench tech. No contact with things then and less liklihood to bump
a component and damage it/its solder joint.

b.

I performed the above, and everything was set right again. There was a
lot of dust on the fans and quite a bit had caked up inside the power
supply (yes, I even opened up the ps).

I won't wait so long the next time....

But, no; to answer your question, I rarely clean the inside of my
monitors (unless I have to get inside to address some issue).

jak

Most folks rarely notice their focus shifting as well. One has to be
video oriented to notice such things.

This is why I bought the one monitor in the world I could find that
has the highest video bandwidth out there at 185Mhz (now the bastards
are up to 210MHz!). Nice, tight, crisp and clean, CRTs are STILL the
king!

Thank you - I stand corrected.

Ed

It has always been the detriment of TVs (CRTs). Even in the tube
type days. They would be fine when new, but after building up dust,
they start to sing, and circuit settings and calibrations get shifted.

A circuit works until changed, and this stuff certainly does that.
They work after changes as well, but noticeably differently in many
cases.

Just to back the pro cleaning side, when I made my living from servicing
monitors (and before that TVs) every once in a while I'd get one on the
bench with the safety shutdown tripping because of a buildup of crap around
the anode connector or other HV parts, but then I've also had nearly as many
repairs in that people had damaged cleaning the inside when they didn't know
what they were doing!