Spots on display, not pixels

Discussion of hardware issues related to the DM1x/DM41. Please ensure that you specifiy whether the issue is related to a credit card size unit or a "Voyager" unit (DM1xL/DM41L).
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Location: Phoenix, AZ

Re: Spots on display, not pixels

Post by reavy »

Michael told me the limit was 70° C, so I set the toaster oven for 70 and let it preheat throughly before adding the calculator. It took 8 total hours for the spots to be completely gone. There was one instance where the spots appeared cleared until the LCD cooled completely, and one spot returned.
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Location: Australia

Re: Spots on display, not pixels

Post by pauli »

A second cooking in the range 80℃ to 90℃ an the last dot has come good. My DM 16C is happy again.

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Joined: Sat Feb 20, 2021 12:44 am
Location: Cincinnati, OH USA

Re: Spots on display, not pixels

Post by lbrott »

When I received my DM15L, it too had spots on the display. I was able to remove them by:
  • Remove the 4 black screws from the back of the calculator, then remove the back
  • Remove the battery
  • Remove the two silver screws and remove the circuit board from the case
  • Preheat a scientific hotplate to 80C and wait for it to stabilize
  • Place the circuit board face down onto the hotplate so that the display is in direct contact with the hot surface
  • Prop the long edge of the circuit board with a thin wood wedge to keep the circuit board parallel to the hotplate surface
  • The hotplate surface temperature dipped to 78C for a minute, then overcompensated to 82C for a minute
  • When the hotplate surface stabilized to 80C again, a 60 minute timer was started
  • After an hour, the circuit board was removed from the hotplate
  • The display was completely black, then quickly turned many shades of blue / gray as it cooled
  • Within minutes the display was at room temperature and all the spots were removed
An image of the setup:
" ... sp=sharing"

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Joined: Mon Jan 28, 2019 10:40 pm

Re: Spots on display, not pixels

Post by boessu »

rprosperi wrote:
Sat Feb 13, 2021 3:45 am
It's really helpful useful to have a known-good, east-to-follow recipe, though the image of folks popping their machines into the kitchen oven is a bit frightening... DON'T DO THAT FOLKS, he's using a special oven. It's almost impossible to control your kitchen oven at temperature this low; find a friend or a tech with a lab oven.
Quite frankly it depends on how you use the kitchen oven.
If you know FIMO, you know you need an oven thermometer anyway. FIMO needs that because the temperature to harden the putty is exact 110C / 230F. You don't use FIMO seriously without a serious oven thermometer, which you can get from them too: ... r-8700-22/
Even tough it looks like a toy, This thermometer is quite precise and good. If there's one of these lying around somewhere in the kids' craft box, it's a great tool to use for baking your calculators too. ;)
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Joined: Tue Sep 12, 2017 4:34 pm
Location: Rabat, Morocco

Re: Spots on display, not pixels

Post by Boub65 »

Hi All,
I also found some pixel leaks on my DM41L.

I have put the calculator under my car windshield for one hour under Moroccan sun...

it got very very hot, and the LCD was all blue...

... and when it cooled all the pixels were OK!
Sincèrement, Sincerely, 73,

2xDM15L, DM41L, DM42 SN#00855 (+one lost during shipping), DM41X #00707
TI-89 titanium, CASIO fx-cg50 (to play with micropython)

There are three kinds of people in the world: those who know math and those who don't.
Posts: 95
Joined: Tue Feb 06, 2018 9:08 pm
Location: Phoenix, AZ

Re: Spots on display, not pixels

Post by reavy »

It looks like “leaks,” but it seems almost certain that there’s nothing leaking. I’d be interested if anyone here knows the mechanics of what’s happening with the LCDs that exhibit this behavior. I had never seen it before the LCDs in these products.
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Joined: Sun Feb 17, 2019 4:30 pm

Re: Spots on display, not pixels

Post by ctrclckws »

I have some old film cameras with lcd display panels that have bled. Replacements are probably not available.
DM10, DM10L: 00031 / DM11, DM11L: 00112 / DM12, DM12L: 02074
DM15, DM15L: 11069 / DM16. DM16L: 02001 / DM41, DM41L: 00859
DM41X: 00036
DM42: 3108
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