hp-15C faceplate

[Flare]

Please see the attached image of my 1985 15C.
I did some research but I reckoned you guys would know best.

What has happened to the faceplate where it is white/grey?

I have read there is a clearcoat, has this been scratched away allowing the aluminium to oxidise? The white parts seem to be raised but I can't get it off with IPA.

I was thinking of following the guide in post 10 of this thread:
https://www.hpmuseum.org/cgi-sys/cgiwrap...ead=153539
But I would like to know exactly what the issue is before sanding it.

Is there a known way to deal with this, also did that book on calculator restoration ever materialise?

Thanks.

[Mark H. Shin]

I have a 10C which had some of the same appearance as your 15C...

The face plate is actually painted on top of the base aluminum.

Therefore, if you carefully mask the display and the logo, you can use a paint thinner/cleaner (I recommend XTREME AK470 Thinner & Cleaner and hobby masking tape available at any hobby shop) with a Q-Tip to remove the entire paint layer, at which point you'll be left with original base aluminum. I would recommend against sanding, as that would negatively affect the original brushed aluminum look!

Which makes it look much better...



Edit: I was planning to airbrush it with new paint (Stainless Steel; also by XTREME), but the look of the original brushed aluminum grew on me and decided to keep as is...

[Flare]

Thank you very much for your advice, it was exactly what I was looking for. Yours looks great so I hope I can manage something similar.
Does it help to seal it in someway afterwards? I wonder what the reason for painting it in the first place was.
Is the lowered bezel around the display a different material in some way? On mine it looks a light grey and some is flaking.

[Mark H. Shin]

The lowered bezel is also painted. On mine, it was in perfect condition so I left it alone.

You could also strip that, being very careful not to let thinner seep into the display area.