The outer coating on my 10BP4 is peeling away. I have not gotten far enough along in the restoration to power up yet. Is this peeling an issue? What could I re-coat with?
Thanks,
Bill B.

Not an issue, it is a conductive coating mostly of graphite in an emulsion.
The coating is for the capacitance filtering of the HV.
If it bothers you so much, you can use a paint that has lots of aluminum in it.
Like rustoleum aluminum paint. follow safe procedures when using flamible paint.

That's a suggestion I hadn't heard before. I don't see why it wouldn't work. You can buy a special spray paint for this but it's expensive.

Thanks guys. I'll go with the alum paint. I kinda figured the coating was conductive since the tube sits on copper grounding strips mounted on the chassis.
Bill B.

In my experience the external dag (deflocculated Acheson graphite) coating on the kine needs to be present and grounded in many television sets, as electrostatic radiation of horizontal sweep signals can raise havoc with other circuitry, causing sync instability, undesireable images on the screen, etc. But in some sets I found that it didn't seem to matter much that the coating had all flaked away. I suppose that the "doorknob" capacitor found in the doghouses of most sets would sufficiently filter any such trash, but I guess not in some cases....

The conductive coating used to be available through General Cement--in both aerosol and brush-on forms, IIRC. Not sure where one would get the stuff now.... :dunno:

They used to make an aquadag spray can... Not sure if they still do, but that's what I'd go for if available. I bet Hawkeye has a contact for aquadag, but that would be for use in a spray gun.

Charles

http://search.yahoo.com/search?p=EMI+Shielding+spray+paint&fr=yfp-t-501&toggle=1&cop=mss&ei=UTF-8

I've stopped loose aquadag from falling off just by brushing water over the tube and letting it dry. It's water based, so wetting it seems to cause it to re-adhere to the glass.

I've stopped loose aquadag from falling off just by brushing water over the tube and letting it dry. It's water based, so wetting it seems to cause it to re-adhere to the glass.

Ayep! Yes indeed!

But you have to get it before the pieces are entirely lost. AMHIK.

But if you are going to be a scrub nurse for a kinescope you'd best have a jumper between the anode connection and what is left of the outer coating. :thmbsp:

Otherwise at least post vids of your activities, discoveries and resultant observations. :D

Edit; Soapbox time here: There is never any such thing as a fully-discharged kine!!!! Read this and heed it if you will. Glass can retain residual charges through a process of adsorption. Thus a successfully-discharged CRT can sometimes self-recharge to bite you when you thought it was finally laid to peace in the emf department.

I used to blame this phenomenom on my own forgetfulness.

The latest that shares this info I have is http://www.repairfaq.org/sam/crtfaq.htm

Read it as you may FYI--be such as it is. It at least tells me that God or Fate is not out to kill me whenever I handle an old kine.

Like firearms the CRT should never be assumed--or even mildly considered--an "unloaded" device.

The outer coating on my 10BP4 is peeling away. I have not gotten far enough along in the restoration to power up yet. Is this peeling an issue? What could I re-coat with?
Thanks,
Bill B.

http://www.waleapparatus.com/catalog.asp?prodid=548677&showprevnext=1

Here's a product (Slip-Plate) that fills the bill and the price is right. The last can I bought, 12 oz. aerosol, cost $6.28 - purchased two years ago, at W. W. Grainger (Grainger's) in South San Francisco. They have 425 branches in the U.S. so there should be one near you.

The basic ingredient is graphite in acetone and petroleum solvents.

This is from the label: "Graphite is electrically conductive and may cause short circuits or other electrical malfunctions." Perfect!

I've heard that the bulk of the customers for this product are farmers who spray it on surfaces that typically gum up on harvesting equipment.

With careful removal of the old dag and appropriate masking of your tube and careful application it will come out looking factory fresh. I use a paper towel cardboard over the neck and cut a nice circle of Contact paper over the anode socket to closely duplicate the original dag coverage.

Roger

BTW, the Slip-Plate can describes the finish color as "dark gray." Trust me, it's the same color as the finish they put on at the tube factory.

Roger

Here's a product (Slip-Plate) that fills the bill and the price is right.

Interesting! Is that really a paint-like product in that it will adhere to surfaces without rubbing off easily? The graphite sprays that I've seen are basically powdered graphite suspended in a 'carrier' solution that evaporates. ...Which is great for lubricating small mechanisms, but if you were to just spray it on a large flat surface like the outside of a CRT, the graphite would probably rub off at the slightest touch, and end up everywhere.

Excellent question Whirled One. The answer is that it is definitely in the "paint" category. It's not a can of Pledge. The solvents evaporate and it leaves a very nice coating which I find virtually indistinguishable from the original. I just presume that others have had the same experience I have had with old RCA's roundies shedding their Aquadag like autumn leaves. Perhaps RCA had a prepping problem.

Roger

Since I was not in a rush, I placed an order with Grainger's and got the Slip Plate. With shipping and sales tax, it came to just over $12. I scrubbed the 10BP4, removing all the loose stuff. The Slip Plate went on easily, just like paint, and I can't see any difference at all from the original coating. I have not not yet put my set back together, but this old roundie looks like it just came from the factory. Thanks for the suggestions.
Bill B.

Before putting it back together, please measure the resistance across opposite sides of the 10BP4 with a VOM. Should be pretty close to 0? Let us know the results. Thanks.

I would like to revive this thread, wherein, last spring, I put in my two cents worth about a less pricey solution to our flaking Aquadag. It's Slip-Plate, available in an aerosol can from any W.W. Grainger location.

In the last post from the end of May, Kirk suggested some resistance checks across the Slip-Plate coating. That seemed appropriate to me and now I've finally gotten around to it. This would be a bit of testing to see whether we can have confidence that the Slip-Plate is electrically suitable as a substitute for the Acheson Industry's Aquadag – which I believe is now a bit more pricey than Bailey's Irish Cream.

We know the Slip-Plate's color looks exactly the same as 'dag after application. It's adhesion and resistance to abrasion appears to be as good or better. 'Dag's carrier is water, Slip-Plate's is acetone, etc. Could it be that for the inside of a CRT, the water base is required? Could the water base be a poor choice for the outside? – but was mistakenly used at the factory – or that it was good enough for five years but not fifty.

The Slip-Plate's label says it’s "electrically conductive." But its web site does not put a number on that electrical conductivity. My online research didn't come up with any easy protocol for measuring that. I'm not a paint chemist – let alone a "coating applications engineer with NASA." Needless to say, I'm not a capacitor designer either. But let's not forget that we're dealing with glass bottles – not a space shuttle. Perhaps others can comment about the downside of trying to use a CRT with most of its 'dag missing. I do know that a peeling CRT is much less shabby with the smart new coat of graphite – pulverized pencil lead.

Anyway, I had a nice test surface – the funnel and face plate portion (all that was left, thank you UPS) of a 10BP4. I proceeded to knock off the big flakes. Methylene chloride paint solvent with some steel wool easily finished that job (of course, avoid skin contact or breathing the fumes). It was now clean as a whistle. I sprayed on a new coating of Slip-Plate. Nothing critical, just about the way you'd put some cheap spray paint on a kitchen chair. (When I do a working CRT, I do take the time to try to duplicate the factory masking of the neck, the anode area, and a couple inches back from the face plate.)

With no phosphor to protect, I did the major drying in the sun, with a little oven baking just to make sure all the solvent was driven out. For convenience, I used a little ancient digital auto-ranging RS multimeter to measure the resistances. (checked it against my big VTVM as a basic calibration check.)

I measured my fresh paint job against the existing good 'dag on various 10" and 12" roundies. Basically, the Slip-Plate was "in the middle of the ballpark." The range among what appeared to be factory coatings was about what you would expect from different factory setups where coating thickness is, perhaps, not that carefully controlled. There was expected variance depending on the separation between the probes. There was also variance in different locations (with same probe separation) on the same tube.

One of the CRT's I tested was a new 12KP4 (base has RCA "stencil font" logo) and its 'dag also tested right in the neighborhood – about the same as the Slip-Plate job.

My conclusion is that the Slip-Plate material is a good substitute for those of us who are on a budget – most of us – maybe all of us now.

I would welcome any comments about your own experience or your own musings – whether you are a NASA engineer or not.

Roger

I should have done this first.

My Sylvania Characteristics of Cathode Ray Tubes from 1959 shows a coating capacitance of 500 uuf min. to 2500 uuf max. for a 10BP4. It wants 750 – 3000 for a 12LP4.

I got out the old Heathkit IT-11 cap checker. I measured from the 2nd anode button to the outer coating of my freshly Slip-Plate coated neckless 10BP4

The reading was 900 uuf.

The reading on my new RCA 12KP4 is 1100. The Sylvania reference is 500 – 2500 for the 12KP4.

How thick is the Slip-Plate coating that I sprayed on? It was enough so that I could no longer see the glass underneath.

Would someone care to confirm these results for us?


Roger

This is probably too late to be of help but aquadag is still available. You can find some resellers if you google it.

I also found out the hard way that Krylon Flat Black spray paint is highly conductive. Nearly as good as Aquadag and much less expensive.

I got a great rebuild from Hawkeye but the coating was brushed on so thin I can see the glass between the bristle marks and I touched a spot and it flaked off far too easily. Never had time to call Scotty about it and it's been over a year now.
Now if only we can find a clear liquid to glue the safety glass back on. I keep worrying that the safety glass could crack much easier if bumped hard than if it were glued on properly.

Do you know how the safetyglass was removed? Was it glued over the whole surface? I use a number of different optical coupling compounds, epoxies and glues in my work. Maybe I could suggest something, but I don't know how the glass was attached originally.

would have been a liquid poured in between the glass and CRT, covering the entire viewing surface, forming to a crystal-clear, rubber-like sheet about 1/8" thick.
I had removed the glass by lightly heating the center area with a hair dryer. The outer areas were seperated because the material was rotted by some white mold-like substance. Thanks for thinking about it.

would have been a liquid poured in between the glass and CRT, covering the entire viewing surface, forming to a crystal-clear, rubber-like sheet about 1/8" thick.
I had removed the glass by lightly heating the center area with a hair dryer. The outer areas were seperated because the material was rotted by some white mold-like substance. Thanks for thinking about it.

I would have recommended RTV-615, but the price has gone through the roof. Sylgard 184 would work, but will still cost about $100 assuming no mistakes. I've not used Sylgard 527. but it sounds like it would work and be less expensive. It would be a very soft layer.

The problem is that 1/8" over 10" diameter is 644 ml of material. The Sylgard 184 0.5kg kit would provide about 485 ml since it has a density of 1.03 You'd want at least 20% more than 644 ml to work with. So, you'd need to buy two kits.

The 527 is much less expensive, but less rigid. Over such an area I don't know that it would be an issue.

After mixing either of them you would need to vacuum degas them to get the bubbles out. Silicones are pretty permeable to oxygen and if you don't degas it some of the oxygen may form bubbles when it cures even though you didn't see any to start with. On the other hand, often small bubbles will dissappear during the cure if you degassed it to begin with. They just get disolved into the silicone.

You would have the safety glass face down on a soft surface that keeps it from rocking. If it wouldn't be distracting, the easiest thing would be to superglue three 1/8" thick disks around the outer edge to act as spacers. Pour the silicone into the center without entrapping bubbles. Then slowly lower the CRT touching the center first in only one spot. Being care to not wiggle about continue lowering it letting the contact spread slowly outward displacing the air. Done carefully, there will be no bubbles. It's important to have only one contact spot to start with.

The cure of these materials is inhibited by contaminates. Vinyl tape, anything with plasticizers, oils etc. will cause them to not cure.

Acrylic resins would be less expensive but are quite hard and shrink a lot during the cure, which might damage the CRT.

They probably used some heat curing or melting polymer that would be difficult to work with, without the proper equipment.

It's important to try a small sample of the encapsulant to see how it cures and applies.

It cures slowly so you have time to take things apart if it doesn't look good and you only lose the cost of the silicone. It's a bit difficult to clean up in such a case. The safest solvent would be 200 proof ethanol or denatured ethanol.

No guarantees.

There are special primers to increase the adhesion to glass. I wouldn't recommend it because you might need to take it apart later.

Oh, and when you pump on it to degas it, it's like soap. It really foams up before collapsing into a clear pool. You need a large container to start with or else be extremely patient. The latter is probably required. It might work without degassing, but for my applications I can't risk that.

http://www.ellsworth.com/display/productdetail.html?productid=263&Tab=Vendors

http://www.ellsworth.com/display/productdetail.html?productid=216&Tab=Vendors

After thinking more about it I believe the layer may be as thin as 1/16". I would measure a piece I saved if I go about this process. Another member here is likely to know the exact thickness.
Again, Thank you very much.

I have a housekeeping comment. Although I wasn't the original poster to this thread, I think the thread is straying from the original topic. This very valuable discussion of "cataract surgery" on color CRT's of a certain vintage should attract more response if a moderator or jeyurkon or JB5Pro could move it, with an appropriate title, over to the AK Early Color Television forum.

Roger

I have a housekeeping comment. Although I wasn't the original poster to this thread, I think the thread is straying from the original topic. This very valuable discussion of "cataract surgery" on color CRT's of a certain vintage should attract more response if a moderator or jeyurkon or JB5Pro could move it, with an appropriate title, over to the AK Early Color Television forum.

Roger

Sorry, I'm new at this. I didn't see where JB5Pro said what type of CRT he has. Do only color CRTs have safety glass applied this way?

I agree that we strayed from the thread. Guess I should have started a new one. I'd be happy to move it, but I have to figure out how to do that first.

John

I agree, interesting information. There were bw tubes made that way, mostly in the sixties, but it was more common with color. There is a good thread out there detailing all the methods of repairing cataracts on those bonded tubes. I recall speculation in the past regarding what was originally used and how it was done. It would seem that cost would be the stumbling block here.

I was speaking of a 21FJP22 which is a color CRT.
Thank you

No apology necessary. Believe me, JB5pro, I know how easy it is to stray. We do it all the time in ordinary conversation. That's how most of us process with our brains - one thing leads to another. That's especially true of those of us who have been around long enough to accumulate a bit in our brains (along with a garage full of old TV's). But, that's another topic - and now, I'm trying not to stray too far.

With forum posts, I try to keep in mind those who might want to look something up - whether tomorrow - or long after we're gone from the scene. Isn't that what makes this forum so valuable? My own rule is that if what I have to say doesn't speak directly to something in the title, then it probably belongs under a new title - or added onto some other existing thread. Now, it's time for me to do as I say.

But does "straying" deserve a thread of its own? Probably not. Now, I'll have to do a search on "straying" just to see if such a thread exists and whether I've missed anything.

Meanwhile, anyone have any more info about the flaking aquadag problem?

After thinking more about it I believe the layer may be as thin as 1/16". I would measure a piece I saved if I go about this process. Another member here is likely to know the exact thickness.
Again, Thank you very much.


JB5pro, I glued two 8" diamter watch glasses together to see how it would work. If you like me to send them to you to look at just send me a private mail with your addess.
John

Speaking of 10BP4 tubes, how abundant are these tubes to get?

Steve

They are fairly easy to come by, given there age. A huge list of sets used them. If you need one, I think Harry Poster usually has them for sale.

Tractor Supply sells an equiv. product called:
EZ-Slide Graphite Based Coating Paint.
A 12.8 oz. aerosol can sells for <$7.
Mega Power Graphite All Purpose Lubricant is available
at auto stores, also a aerosol can spray.