HP 48GX calculator - dot matrix display - darker spots - Page 1
Forum section: electronics / beginners

author: ergya
author_rank: Contributor
timestamp: January 03, 2022, 07:02:41 pm
content: Hi everyone,Just got my sexy HP 48GX calculator from ebay (used) and it has 2 darker (almost) circular areas on the display 1 is more prominent the other is barely visible. The display itself works, the pixels change accordingly even around the problematic area, readibility is fine too but still there and it is annoying me (this caculator is not the cheapest). Even if I turn it off the darker areas are visible.I attached 2 images: 1 image is when it is fully turned off, the image does not really give it back the difference but with my eyes it is much more apparent, the other is when it is turned on but with low contrast settings so that you can see the difference. 1 more interesting detail it seems the pixels (or the display, maybe not "pixel" issue) get gradually darker toward the center of the "circle" and starts fading when moving away from it + it is irrelevant from what angle I am looking at it.Could you please advice what the issue could be with the display? Is it oxidation or something else? I don't see any scratch or any other physical damage that would explain this. Have not dissassambled it yet to look at the back side of the display (and don't really want as it is a bit of pain to do it with this calc). To me it looks maybe pixels burnt in but never seen this happening with this type of dot matrix displays only with my old color TN panel monitor that had some "icons" burnt in.Thank you

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 03, 2022, 08:00:32 pm
content: The usual culprit for this kind of 'damage' to an LCD display is either excessive pressure on the panel - the calculator may have been stored for a long time with something stored on top of it - or elevated temperature. The effect is likely a small leak around the dark spots.In any case, I don't think there's anything you can do about that except replacing the display.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 03, 2022, 08:56:56 pm
content: Oh, and given it looks relatively minor, replacing the display (if you can find one) is probably not worth the trouble. There are many tutorials out there that explain how to open a HP48G/X. It's not quite fun. =)

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 03, 2022, 09:03:30 pm
content: I have both the 48SX and 48GX. Their display have so low contrast that I now use the emulator instead.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 03, 2022, 10:39:07 pm
content: Quote from: BeBuLamar on January 03, 2022, 09:03:30 pmThat's "interesting". Would you say that contrast has always been too low for your taste, or that it's gotten worse over time? (And, sorry for the obvious, but did you adjust the contrast?)I have a 48G+ and, the case is a bit worn out in the corners, but other than that, it still works perfectly, and contrast is pretty good. But it has the "black" LCD display, while I think many 48SX/G/X had the "blueish" LCD display, which was much lower constrast. Would that be the kind of display your 48's have?

author: ergya
author_rank: Contributor
timestamp: January 03, 2022, 11:34:08 pm
content: QuoteProbably this is the reason. I have been looking at the screen from different angles and different light sources and found some very faint circular discolorations around the problematic areas (but nowhere else) which is a direct sign of a micrometeorite impact. Jokes aside very likely something was on top of the calculator and that caused the issue.QuoteYeah, I checked a few videos before asking and immediately knew this is not something that I would do. I would just make things worse.Anyways, thank you for helping me with this.BTW while randomly looking around I found this below, this calculator has the same sympoms but it is significantly worse than mine.

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 03, 2022, 11:45:43 pm
content: Quote from: SiliconWizard on January 03, 2022, 10:39:07 pmNo they are always to low in contrast. The 48SX is worse the GX isn't as bad but not good. They didn't fade but simply too low in contrast and hard to see in low light. You really need bright light to see well. Besides they are a little bit slower than the emulator and nobody steal my emulator software running on my PC at work.

author: rstofer
author_rank: Super Contributor
timestamp: January 04, 2022, 01:09:40 am
content: If you want a bright display, try the HP Prime Graphing Calculator. I prefer the HP 48GX but both are on my desk.I use the Free42 simulator on my cell phone - it's pretty nice.There is a problem with old eyes and none of my calculators use a large enough font.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 04, 2022, 01:14:02 am
content: Quote from: BeBuLamar on January 03, 2022, 11:45:43 pmOK, but you didn't say if those are the blueish LCD displays or not. I suspect they are. I think the fully black LCD ones were introduced in late production, so having them would all depend on when they were manufactured. The black LCD ones have much higher contrast.

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 04, 2022, 10:19:27 am
content: Yes my 48GX has blue LCD. It's version P.

author: Venturi962
author_rank: Regular Contributor
timestamp: January 06, 2022, 01:06:48 am
content: You can find a donor Black LCD from later HP Saturn Calcs (HP 49G, 39G, 40G) and swap for a better experience. As mentioned, opening these calculators to do the swap is a bit of a fiddle, the method that I've had the best success with is here:https://www.keesvandersanden.nl/calculators/downloads/Opening_the_HP48_by_Han_Duong.pdfAnother guide here:https://www.hpcalc.org/details/9014

author: ergya
author_rank: Contributor
timestamp: January 06, 2022, 02:42:25 am
content: QuoteThank you for the links. I spent some time a few days back on this topic and honestly the more I look the more HP 48xx I find with similar problem (severity varies, looks mine not the worst at all) on Reddit, Youtube and on eBay. People just posting images of their calculators not even complaining about that issue. Interesting.