Retr0brite problems

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jonb
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Retr0brite problems

Postby jonb » Wed Jul 19, 2017 1:48 pm

Hi

I'm experimenting with Retr0brite as I have lots of beige plastic to restore, but it's not going terribly well.

I saw some yootoob vids; one of then demonstrated using a hydrogen peroxide cream as-is, because it is already thick enough to stay where painted, and the oxygen bleaching agent you are supposed to add is a catalyst (accelerator, so not necessary if you don't mind hanging around a bit).

I got me some generic "creme peroxide" (12% / 40 vol) and mixed a little with a small amount of Vanish carpet cleaner, which contains some of the oxygen based bleaching agent. Then I took a single key cap that was yellowed and put it in a little tray. I painted it with the mixture and put it into a UV eraser that is used for clearing down EPROM chips. It's been in there all day, but so far I can discern no improvement in the yellowing, despite periodically recoating the key cap.

I must be doing something wrong - anyone got an idea what it might be?

Cheers
JonB

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1024MAK
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Re: Retr0brite problems

Postby 1024MAK » Wed Jul 19, 2017 2:22 pm

Are you sure that the wavelength of the EPROM's UV light is suitable for this? There are various "bands" of UV light.

Normally when Retr0briting, users report either using sunlight or a sun bed UV lamp (as used for tanning skin).

In electronics, the UV lamp used for EPROMs is a different wavelength to the UV lamp used for developing photosensitive PCBs, both of which are different wavelengths to sun bed UV lights.

Mark
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jonb
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Re: Retr0brite problems

Postby jonb » Wed Jul 19, 2017 3:24 pm

That never occurred to me... I probably need a bit more patience, too.

Here is the result - the 7 key was the test subject. Prior to the experiment it looked like the 4 and 8 keys.

IMG_0969.JPG


I need to get a tanning lamp as I don't trust the lousy UK weather. Expensive.

More thoughts (for which I would appreciate your comments!)
  • I saw a video where liquid peroxide was used in a translucent plastic box to avoid drying / streaking but in liquid form it's expensive.
  • If you really don't need an oxygen catalyst, a liquid bath of peroxide (handled carefully) could be reused several times. One of my concerns with the creme based approach is wastage.
  • Another video I saw showed a small bath suspended over a counterfeit note detector (UV lamp used in banks and shops), being moved back and forth by some motorised Lego Technic contraption. It was being used to Retr0brite key caps and ensure even coverage (of the UV light).
Last edited by jonb on Wed Jul 19, 2017 3:39 pm, edited 1 time in total.

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topcat96
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Re: Retr0brite problems

Postby topcat96 » Wed Jul 19, 2017 3:30 pm

UV eraser lights have wavelengths shorter than 400 nanometres.

Sunlight is usually defined as having wavelengths in the range of 400–700 nanometres (nm).

It's been widely reported that UV Eprom eraser lights just aren't strong enough to kickstart the Retrobright process. Recommended to get a cheap tanning lamp instead.
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jonb
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Re: Retr0brite problems

Postby jonb » Wed Jul 19, 2017 3:42 pm

I'm coming to that conclusion...

Are the LED UV lights of any use for this, or should I stick to the fluorescent tubes?

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topcat96
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Re: Retr0brite problems

Postby topcat96 » Wed Jul 19, 2017 3:47 pm

jonb wrote:I'm coming to that conclusion...

Are the LED UV lights of any use for this, or should I stick to the fluorescent tubes?


Stick to fluorescent tubes. Tried and tested, good results - you can't go wrong with them.
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1024MAK
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Re: Retr0brite problems

Postby 1024MAK » Wed Jul 19, 2017 6:21 pm

UV LEDs: Keep in mind that a lot of things are advertised as having UV LEDs, but the UV LEDs only output light in the visible part of the Spectrum, so don't actually output any UV light...

Where as proper UV tubes do output UV light.

The key is to look at the specifications. If the seller/supplier does not give the power output at a specified frequency/ wavelength, don't buy it.

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jonb
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Re: Retr0brite problems

Postby jonb » Mon Jul 24, 2017 12:21 pm

Well, I bought one of these: http://www.philips.co.uk/c-p/HB175_01/facial-tanner

It uses 4x15w Philips Cleo Compact tubes:
  • Power consumption : 15W
  • UVA 2.3W
  • UVB 1%
  • UVA mw/cm squared : 25

No indication of the specific wavelengths emitted but from what's been said I should be OK.

Full details http://prolight.info/pdf_specs/Philips_Cleo_range.pdf (although this is a consumer level spec).

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jonb
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Re: Retr0brite problems

Postby jonb » Mon Jul 24, 2017 12:35 pm

So the next question / proposal...

To apply Retr0brite to a set of key caps, they need to be held in position somehow. I thought it might be interesting to remove all the keys from the switches, lay cling film over the switch stems, then reattach the keys with the cling film still in place. The stems should poke through the cling film, and they'll hold the keys in position for peroxide and UV application. The cling film would prevent the peroxide from getting to the switches or PCB, and can be folded over for that fetching "prevent the gunk from drying" effect.

Any comments on this? A bit risky, perhaps? Or worth it?

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1024MAK
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Re: Retr0brite problems

Postby 1024MAK » Mon Jul 24, 2017 3:26 pm

Hmm, not keen on that idea. You only need a hole or tear in the cling film and the peroxide could then drip into the switches and then onto the PCB :twisted:

And of course, if (as they should be) the caps are a tight fit on the switch stems, pushing the two together may well break the cling film. So I suggest a "dry" run first :wink:

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topcat96
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Re: Retr0brite problems

Postby topcat96 » Mon Jul 24, 2017 4:28 pm

Best to remove the keys and place them into a tub of retrobrite solution and weigh them down a little so they are fully immersed.
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