Can adhesive aluminum foil tape replace aquadag on a crt - Page 1
Forum section: electronics / repair

author: c32
author_rank: Newbie
timestamp: April 29, 2019, 09:02:33 pm
content: While cleaning a CRT I discovered that it had some black paint on it and assumed it was some kind of dirt so I cleaned up a portion of it, but then I found on the internet that it was a conductive layer needed for the CRT grounding.My question is whether I can use some cheap eBay aluminum foil tape or do I need the real deal, if so can I get it anywhere cheap?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 29, 2019, 09:08:42 pm
content: Yeah, probably. Make sure it makes electrical connection to ground (the adhesive may not be conductive). Probably just cover some area under the spring thing that touches it.Tim

author: Gyro
author_rank: Super Contributor
timestamp: April 29, 2019, 09:15:04 pm
content: How much (what proportion) did you remove, and is the grounding spring still in contact with what's left?The internal and external coatings, together with the glass, form a reservoir capacitor for the EHT. If you haven't removed more than a small portion and the remainder is still well grounded, then a small reduction in capacitance won't make any significant difference.P.S. Be careful of sharp foil edges anywhere near the EHT connector cap - grounded sharp points too near the EHT connection can generate corona discharge nearly as well as sharp points on the EHT connection itself.

author: c32
author_rank: Newbie
timestamp: April 29, 2019, 09:53:26 pm
content: I think a little less than one third, I only removed some on the top. The dag cable is connected to some wipe contacts on the bottom of the crt and this part is intact with the original aquadag.Also could that be related to the amount of static charge/discharge noise when the screen is turned on or off because I think it increasedFrom reading a bit on the internet I think it would normally discharge through the aquadag but if there is less of it it will also discharge through the air and cause more of this noise and a bit of a shock if you touch the screen and ground when turning it off

author: pbarton
author_rank: Frequent Contributor
timestamp: April 29, 2019, 10:00:31 pm
content: Painting your tube with Aquadag, skip to 1:24:49

author: c32
author_rank: Newbie
timestamp: April 29, 2019, 10:06:45 pm
content: QuoteThat's amazing!Coincidentally that's exactly the video i watched and realized that black stuff was put there intentionally and called "aquadag"I really like how there are still people rebuilding and repairing CRTs

author: c32
author_rank: Newbie
timestamp: April 29, 2019, 10:13:01 pm
content: Actually reading at the comments he quit this 52 year-old business because there wasn't enough interest in fixing old crt TVs, to became "an athletic trainer and coach" (?)"Avitt plans to donate his tube rebuilding equipment to the Early Television Museum in Ohio, and has volunteered to instruct others in its operation if there's sufficient interest. "

author: james_s
author_rank: Super Contributor
timestamp: April 30, 2019, 02:26:21 am
content: I've had the aquadag flake off a tube before, I used some carbon paint sold for shielding electric guitars, it seems to be pretty much the same stuff.

author: Gyro
author_rank: Super Contributor
timestamp: April 30, 2019, 08:52:46 am
content: Quote from: c32 on April 29, 2019, 09:53:26 pm"a little less than one third" falls nicely into my 'not sure' range! If you'd said 50% I'd say too much, if you'd said 25% I'd say it's fine. So it's a bit less than a third then it'sprobablyfine.It sounds as if the grounding of the remaining aquadag is nicely intact - you'd see internal sparks to the spring or hear a loud crack otherwise. I think the reason for a little more static sound at turn on and off could possibly be because the lower capacitance allows the EHT to rise and drop faster, the same with the increased static feel on the screen (you always get a fair amount anyway). It could just as easily be that you have now 'fixated' on it because of what you did, whereas before, you simply weren't listening or conscious of it. You don't normally go feeling for static day-to-day. To me, CRT TVs always seemed to make a bit more static sound after a good cleaning anyway.The real test of insufficient EHT capacitance is sudden picture size changes when scenes change on the program, especially going from a dark to light scene - there is always a little but if it is now excessive and distracting then you probably need to do something.I would go for James's suggestion of carbon paint if you really do need to do anything. Aquadag is a fairly high resistance coating anyway. Thinking overnight, Aluminium tape might be a bad idea - if it eventually curled up with the heat and fell down into the electronics, you would have real problems! Otherwise, I'd leave it alone, it won't cause any damage to the circuit.