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Re: Spots on display, not pixels

Posted: Sat Feb 13, 2021 5:10 pm
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.

Re: Spots on display, not pixels

Posted: Mon Feb 15, 2021 6:36 am
by pauli
A second cooking in the range 80℃ to 90℃ an the last dot has come good. My DM 16C is happy again.


Pauli

Re: Spots on display, not pixels

Posted: Sat Feb 20, 2021 8:08 pm
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:
"https://drive.google.com/file/d/1ATwgjS ... sp=sharing"

Image