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Advent 400 table radio de-yellowing

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I decided we needed to change up to a better radio in the kitchen and I had the Advent 400 powered receiver but still needed to find the matching speaker. Now the unit I have has been in storage almost 20 years and the white plastic casing has yellowed like an early Apple computer - pretty nasty. I have read that some people have had luck with re-finishing so I went at it slowly with sandpaper - 600, 1000 and then 1600 grit wet sanding and then two steps of polishing with my automotive polisher, clamped in the vise so I could manage the delicate plastic. It came out nice but if you look closely at the pic of the back, you can see the yellowed colour of the un-restored back panel. I found a speaker nearby (yay!) on line and had it sent up and, since this was also yellowed, I proceeded with the same sanding and polishing process to get a matching look. It looks great and sounds even better. Thanks to this Forum I also feel confident that there is still communication and support for older electronics, including some good info on changing components, like capacitors if the volume falls off or if a speaker needs new suspension. Analogue is always fix-able.



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Welcome bhart

Nice work! As you discovered, no amount of bleaching or cleaning will remove the yellow. The only way to restore the original white finish is what you did: a painstaking process of sanding and polishing. Your work came out great!

I have seen white painted 400s and to my eye they look wrong. I took a radical approach in refinishing mine: Spray on a black pebble finish and replace the scratched and flaking faceplate with a new, slightly different looking reproduction. Here's the story: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/8443-advent-400-table-radio/&tab=comments#comment-103448-Kent



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Thanks JKent,

Yes, your's was one of the postings I found early on in my searches. Painting was in the back of my mind if the polishing did not turn out. Plastic surface finish is quite sensitive to heat, especially from a 8" polishing wheel. I have owned a number of black cars over the years to help me perfect my technique.

I did end up with a bit shinier surface on the receiver than the speaker, with the speaker being closer to original. If I have to service the amp, I'll try and re-sand with 1600 and then go a bit easier on the polishing to get the correct look. Right now, it's fine for me. 

Had the speaker apart while cleaning up and the cone suspension is fine. No whizzer cone and the speaker is original and a 'made in Canada' unit. I flipped the blackout paper to the better side, pushed out a small dent in the grill and cleaned up the rubber surround with automotive rubber protector to get a clean look. All the internal stiffening Masonite bits are still firmly attached and the foam is 100%. Very well built unit.

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  • 4 months later...

Sorry to necro bump this. Haven't been on in a while and just read this thread. These old electronics yellow because of a fire retardant added to the plastic. Yellowed plastics actually can be restored using a process called "retrobrighting". It's a pretty popular process in the vintage video game and computer crowd. Short version, you coat the yellowed plastic in a highly concentrated peroxide and expose to uv light(the sun works well). Most plastics can be restored to a new, or close to new appearance. Here's a couple pics of a game system i did to give you an idea of how well it works:



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Thanks for the tip.

I’ll have to research that and give it a try (although I do like the look of the black pebble finish)

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