SwissMicros Calculator Forum

Michael told me the limit was 70° C, so I set the toaster oven for 70 and let it preheat thoroughly 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.

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


Pauli

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"

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:
https://www.staedtler.com/intl/en/produ ... 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.

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!

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.

I have some old film cameras with lcd display panels that have bled. Replacements are probably not available.

After owning a DM41 for nearly a decade, the display began exhibiting the now famous "ink-blobs" this year, —and many of them.

Michael reached out via email and shared the heating trick.

Taking his advice, I dismantled the calculator and positioned the PCB, with the display facing downward, on the hot plate of a 3D printer. I set the plate temperature to 85°C and completed three cycles, each lasting 30 minutes.

Hope this helps others.