protecting dielectric lens on antenna that needs new paint job - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: November 19, 2019, 03:48:56 am
content: I want to make some horn antennas I have not look like they were pulled out of a scrap dump circa 1960.They have flaky paint over copper, the problem is that they are not open horns but ones with plastic dielectric lens (the kind that look like a topographical map) on the cover. The caps are glued into place and I don't want to disturb them.I am worried that paint stripper will end up fogging/destroying the lens (the new non methylene chloride goo type).What is a mask I can apply over the top to protect them? I was thinking that I would carefully paint the paint stripper on with a rag, but I am worried about fumes.Is masking tape enough? I thought to drip candle wax on it too. Maybe just smearing it with vasoline (I don't think it will effect the plastic).I am more worried about this because I think it might be precisely set during manufacture and I don't want the glue to absorb stuff that causes it to shift over time etc.

author: station240
author_rank: Unknown
timestamp: November 21, 2019, 09:39:40 pm
content: Sounds like you need paint stripper that is safe around plastic.Brake fluid is one liquid that will remove acrylic paint, but not damage some common plastics. Works be getting between the paint and surface and dislodging it.Best to test it on a small area first (eg apply one drop), see how it behaves on the paint/glue/plastic, just to be careful.

author: coppercone2
author_rank: Super Contributor
timestamp: November 21, 2019, 10:59:08 pm
content: Quote from: station240 on November 21, 2019, 09:39:40 pmehh I just got impatient and went with it, the ordeal was a pain in the ass and required numerous reapplications (the only reason I did not go with the die grinder and a strip brush is because I was worried about work hardening the metal) but in the end even after alot of scraping, it still got the treatment (however brisk and gentle).in most cases the primer and paint came off,but in some regions that were flat there appeared to be a layer that did not remove (bondo I think). No idea why, but the threaded plates that were 'welded' to the horn were actually glued to the horn (as I noticed the die grinder made the nasty paint covered 'bevel' disintegrate into what looked like bondo. I think someone just slathered bondo on a steel triangle with a hole in it and slapped it on the antenna, then maybe wiped their tools on the body of the antenna.Not really impressed for what these things used to costThe lens was not really effected, i did clean it up with a few minutes of scratch-x 2.0 from maquires to make it look newer though. I think the masking tape greatly reduced chemical exposure, but it was seriously almost nothing because like 2 minutes or less with scratch-x 2.0 plastic polish made it look great, and it looked oxidized to begin with because its ancient.Anyway, the other horn I actually found out, the dielectric lens was not even adhered into the device, the glue went bad and it was just 'press fit'. And it appears Sylvania did not have great quality control (they had streaks of glue running into the horn body when I removed the lens).Should I be using a special glue to glue it back in, or is standard clear epoxy good enough? I was going to leave it so the glue drips out rather then in this time...