Question about CRT's - Page 1
Forum section: electronics / repair

author: Bashstreet
author_rank: Frequent Contributor
timestamp: December 03, 2017, 12:37:34 am
content: I am salvaging some components from a crt tv and i noticed a "device" in circuit board that has quite a bit of black "dust" it's appearance is of fine carbon powder.What causes such dust ?What is it made of ?

author: Nusa
author_rank: Super Contributor
timestamp: December 03, 2017, 01:21:45 am
content: Too vague. I think we need pictures of what you're talking about.

author: drussell
author_rank: Super Contributor
timestamp: December 03, 2017, 01:32:17 am
content: Any fine dust in the area (which could come from all sorts of things, obviously) is attracted the various high voltage components in a CRT chassis, especially things like the flyback and the CRT itself.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: December 03, 2017, 01:43:57 am
content: Quote from: drussell on December 03, 2017, 01:32:17 amYes i digged around a bit and indeed the device that is most dusty is called flyback transformer.I just wonder why the dust is so dark and has appearance of carbon powder.First i thought maybe the CRT itself causes some kind of carbonation effect.

author: coppice
author_rank: Super Contributor
timestamp: December 03, 2017, 01:53:46 am
content: Quote from: Bashstreet on December 03, 2017, 01:43:57 amMaybe the colour you see reflects where the CRT has been. Its usually just like the grey dust you see when you empty a vacuum cleaner. In other words its just the same dust that is settling everywhere else in the building. It just accumulates heavily where electrostatic forces push it.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 03, 2017, 01:56:35 am
content: The "dust" is particulates from the environment which were attracted to things that have a high voltage charge. The principle forms the basis for electrostatic filters. I have such a gadget filtering the air in my HVAC.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: December 03, 2017, 02:07:50 am
content: Quote from: coppice on December 03, 2017, 01:53:46 amI suppose that would be logical but none of electronic equipment i have in house (that i have repaired opened etc) has such dust.It is always grayish "normal" dust.Now this dust is different it is more dense and finer and is very dark almost black soot like. (not literal soot as there is no burning etc in the set)I would assume it must have something to do with the higher voltages and its effects on dust

author: coppice
author_rank: Super Contributor
timestamp: December 03, 2017, 02:28:33 am
content: Quote from: Bashstreet on December 03, 2017, 02:07:50 amThe dust around those high voltage points is usually denser than the general dust build up due to convection and gravity, as the electrostatic forces pack the particles together.I wonder if you are looking at areas which have operated at high temperatures. That affects the look of accumulated dust, and may darken it.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: December 03, 2017, 02:53:27 am
content: Quote from: coppice on December 03, 2017, 02:28:33 amI do not think flyback transformer as such gets very hot but crt's can get quite warm if not hot .It could be that the "dark" dust is indeed just normal dust but very compacted effect may be helped by the higher voltages/warm hot case.It makes sense to me.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 03, 2017, 06:47:26 am
content: Black dust is probably a sign of a sooty environment (using candles?), or any other kind of dust of that color. Grinding dust, say.The source need not be obvious. After a lifetime of exposure to fresh outdoor air in forest-fire country, I can imagine the accumulated dust being on the dark side. (Someone living in such an area might confirm that suspicion, just speculating.) It needn't be very dusty for very long, nor visibly dusty at all (to any extent that you can see by eye), for visible dust to collect on such things.Tim

author: james_s
author_rank: Super Contributor
timestamp: December 05, 2017, 12:37:01 am
content: One of the places I lived was near downtown and electronics collected a black dust from Diesel exhaust so it may be that. Another common cause are wood stoves and fireplaces. Either way it's nothing really to worry about, I just wash it off. Depending on what these are, many types of CRTs are getting difficult to source and many types are worth saving or finding a home for.

author: Bashstreet
author_rank: Frequent Contributor
timestamp: December 05, 2017, 02:11:20 am
content: Ok lets get this straight i do not use candles nor i live in "sooty" area etc.Reasonable explanation has been already given lets not keep

author: Bashstreet
author_rank: Frequent Contributor
timestamp: December 05, 2017, 03:51:08 pm
content: Thx everyone for ideas

author: Nusa
author_rank: Super Contributor
timestamp: December 05, 2017, 04:29:19 pm
content: Any smokers in your house?

author: Bashstreet
author_rank: Frequent Contributor
timestamp: December 05, 2017, 04:50:39 pm
content: Quote from: Nusa on December 05, 2017, 04:29:19 pmNo.Feasible most likely reason(s) have already been found