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I recently purchased a what was described as probably never used HP48 GX. After receiving it, it appears there is a ring on the screen. It can only be seen at angles. Does anyone have any idea what this is, and what could have caused it?

Looks like deterioration of the polariser on the LCD.

Whether the calculator has been used or not, if it's been exposed to daylight or any other source of UV, this will happen. Remember, these things are about 30 years old...

Hmmm...I'm not sure what happened to my previous reply. As mentioned above one of the polarizers is going bad. I would guess the rear polarizer which also acts as the reflector. I tried repairing a similar failure on a Casio PB-100 using a 2nd hand polarizing film with white paper as a reflector. It worked but is far form ideal. I did just get in some proper reflective polarizing material to give it another try. Link to video I did covering this repair below.

Edit: I think I hit 'Preview' with my previous reply but then forgot to hit post. Silly me...

I have the same issue on that ugly green French Casio three color LCD. The problem vanishes entirely when the calculator gets turned on.

(08-01-2022 01:02 PM)Jeff_Birt Wrote: [ -> ]Edit: I think I hit 'Preview' with my previous reply but then forgot to hit post. Silly me...

@Jeff - You're quickly becoming a seasoned MoHPC user, congratulations. One clear way to see that is admitting the above in a public post! Everyone does it, it's just the honest and more experienced users that admit it publicly as a way to help prevent doing it so again in the future. You'll now surely do it less, but it will happen again, lol.

Thanks for the reply guys. I know it's about 30 years old so it is what it is and the gamble I took. Paid about $180 for it with the box and paperwork, hopefully that wasn't too much. I really bought it to collect, so it won't be exposed to anything more than me playing with it once and a while. Like I said, only really noticeable off angle.

Don't forget hitting the back key after posting to get a double post