cleaning backs of monitor tubes

PrairieDillo

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Last night I was wiping down the back of a tube when I got to that thick black tar looking stuff. After wiping it started to come off. It's different from the layer of dust that most monitors pickup.

Is that stuff from the factory or is it just caked on dust/grime/grease?

I'm just curious if it was a factory spray/coating or just dirt. I've seen it on many monitors but not all.
 
There is an intentional conductive coating on the back of the picture tube - and it will be present on all modern tubes. It's called the aquadag, and it essentially allows the glass of the tube to act as a large capacitor. It's connected to the chassis by way of a spring strap that goes along the bell of the picture tube, which has a wire that connects to the neckboard. Don't scrub it all off...

-Ian
 
Hehe. Yeah, you really shouldn't scrub any of it off... but if you already removed a little, it should still be fine. In the realm of very old tubes (like used in 50's TV sets), sometimes the aquadag coating simply flakes off with age. Some coating missing works OK, but a lot/all the coating missing causes problems. A while back, someone figured out that a graphite spray, intended as a slip-coating, worked as a replacement for completely flaked-off tubes. I think it was called "Lubriplate" or something similar.

-Ian
 
I'm glad I read this 'cause I was going to scrub my monitor down spotless soon.

Generally speaking, it's OK to hose it down. Most modern aquadag isn't water soluble like the old stuff was. I usually take filty/nasty monitors outside on a sunny day, spray them with simple green or something, then hose off the crud and let them air dry. Just, you know, don't go nuts scrubbing away at that coating.

-Ian
 
Oh, ok. So that built-up crusty stuff that looks like asbestos can go? I can rub it off with my fingers.

Yeah. That's just crud and dust that got attracted to the tube from static. The aquadag coating is under that, it looks a bit like dark grey spray paint. It's on there pretty good, but serious scrubbing will take it off.

My procedure for cleaning nasty monitors is:

-Disconnect and remove chassis
-put duct tape over the anode connection on the picture tube (reduces the amount of water that gets in there, don't want the connection to corrode)
-spray back of the tube with Simple Green, let it sit for a minute, then wash it off with the hose
- let the tube sit and dry, you can remove the tape before it bakes to the glass
- after the tube is dry, clean the area right around the anode connection with alcohol or Windex, to ensure it's really clean. Crud here can cause a discharge path.

Similarly, I'll hose down the chassis quick too. This gets the majority of the crud off. Then put it in the dishwasher (top rack, coil up the wires so they don't get caught in anything), and clean with usual dish soap, no heated dry. After that's done, shake out as much water as you can. Set the oven to 150/175 (basically, as low as it will go), and put the chassis on a foil-covered cookie sheet. Let it "bake" for a half hour/45 minutes or so, until it's nice and dry.

You probably don't want to run dishes through along with a monitor chassis. I have put various monitors through the dishwasher over the years, primarily G07's and 4900's. Obviously, clean them, then recap/rebuild. If the width coil on a G07 isn't broken already, might want to desolder it first - they're pretty brittle. If the monitor isn't that dirty, washing it probably isn't worth the effort, I've only done it on ones that were so filthy I couldn't see the components on the board. It's very hard to rebuild/recap a monitor that dirty.

-Ian
 
Thanks, I think I'll do that to my monitor if it ever stops raining. The chassis isn't dirty at all since it came from somewhere else.
 
What the hell do y'all clean it with? I've squirted the backs of lots of monitor like G07's and 4900's with Windex and wiped them down without ever having this issue...
 
Great info guys. Yeah I only whipped edges of that layer off before I was like... this has to be a manufacturer coating.
 
after working at a local oil change shop i too cringe at the smell of simple green, it works very well, but the scent is undeniable.

I remember reading about a special coating or dust that was applied to the tube by the manufacturer a while ago, so i just leave my tubes the way i get them (unless there's soda or puke or cobwebs).
 
What the hell do y'all clean it with? I've squirted the backs of lots of monitor like G07's and 4900's with Windex and wiped them down without ever having this issue...

I've had a few where it would just wipe right off once dampened with anything.
Most don't though.

And just to clarify where the graphite coating is......
 

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