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Post by elorens on Sept 15, 2021 21:57:44 GMT 12
I'm tidying up this radio, recently acquired from the Tip Shop. I have hit a couple of snags on which I'd like some advice, please. First, the clear plastic window in front of the tuning dial is no longer clear, in fact it is quite seriously yellowed. I have tried headlight restorer without success. I'm thinking that I will have to cut a fresh piece of clear acrylic sheet and try to make this fit, but does anyone have any better ideas? Second, the tuning mechanism consists of a flexible metal strip, wound on a plastic drum driven by the tuning knob. The far end of the strip drives a little carriage holding the red tuning indicator needle, as shown in the image. The problem is that the action is very sticky indeed: having pulled the indicator to the right hand end of its travel, it is then very difficult to push it back in the other direction. Has anyone worked on a mechanism like this, and can you suggest any ways of making it work sweetly? Thanks! Lawrence --   |
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Post by Richard on Sept 16, 2021 9:01:38 GMT 12
I've heard that hydrogen peroxide can clear yellowed plastic? maybe someone has done it ?
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Post by Radiotech on Sept 16, 2021 23:04:24 GMT 12
Hydrogen peroxide can be used to remove the yellowing from ABS plastics which have 'faded' as a result of them being made
with Bromine as a flame retardant.
When exposed to UV light, the Bromine molecules destabilize and leech to the surface, turning the plastic yellow or muddy brown.
The plastic window won't be ABS, more likely to be polycarbonate.
Have you tried using the headlight cleaner on the inside of the window?
If that doesn't work, then cutting a new piece of acrylic is probably your best option.
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Post by elorens on Sept 16, 2021 23:21:02 GMT 12
Hydrogen peroxide can be used to remove the yellowing from ABS plastics which have 'faded' as a result of them being made with Bromine as a flame retardant. When exposed to UV light, the Bromine molecules destabilize and leech to the surface, turning the plastic yellow or muddy brown. The plastic window won't be ABS, more likely to be polycarbonate. Have you tried using the headlight cleaner on the inside of the window? If that doesn't work, then cutting a new piece of acrylic is probably your best option. Thanks for this. Yes, I tried the headlight cleaner on both inside and outside, and no improvement. There's a big difference between the window which was exposed, and the edges which had been covered, which are still quite clear. |
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Steve
Society Members
vintageradio.co.nz
Posts: 732
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Post by Steve on Sept 19, 2021 11:25:17 GMT 12
Yep, the retrobright (see some of the videos by The 8-Bit Guy on youtube for some fantastic results) process won't work on the dial window - and if you can't clean it with headlight cleaner (or half a lemon dipped in baking soda - this works on headlights as well I'm told) then you'll need to replace it or live with it because the problem is molecular, not a surface issue.
As to the mechanism - clean the parts well with IPA or something similar to get rid of any old grease or anything causing it to bind - then use a dry-film lubricant like graphite on the metal guide to allow the cursor to slide freely. I use an old CRC product called Dry Glide - which is not cheap but a can should last forever for radio work. Maybe something like a soft pencil would also work?
Cheers, Steve
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Post by elorens on Sept 19, 2021 19:12:34 GMT 12
Yep, the retrobright (see some of the videos by The 8-Bit Guy on youtube for some fantastic results) process won't work on the dial window - and if you can't clean it with headlight cleaner (or half a lemon dipped in baking soda - this works on headlights as well I'm told) then you'll need to replace it or live with it because the problem is molecular, not a surface issue. As to the mechanism - clean the parts well with IPA or something similar to get rid of any old grease or anything causing it to bind - then use a dry-film lubricant like graphite on the metal guide to allow the cursor to slide freely. I use an old CRC product called Dry Glide - which is not cheap but a can should last forever for radio work. Maybe something like a soft pencil would also work? Cheers, Steve Thanks for the tips, Steve. Will try to find that Dry Glide product. Cheers, Lawrence |
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Post by elorens on Oct 13, 2021 8:46:47 GMT 12
Update: job done. New acrylic window fitted, dial slider track cleaned and dry lubricated with graphite, and extent of slider movement constrained slightly. Works fine now and dial calibration is spot on. Replaced battery springs. Works a treat on all bands. Great little radio! Thanks again for the advice.
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