Different characters/artifacts after replacing Optrex DMF5005N LCD

Guy St-Denis

• June 02, 2022 16:43

I replaced an Optrex DMF5005N LCD with an NHD-24064WG-ATMI-VZ# in a Yamaha SY99 synthesizer.

The main display pages work as expected.

However, when I enter the diagnostics pages, there are different characters/artifacts, and characters/artifacts where spaces should be, etc.

Original:
 

Replacement:

Because the main (i.e., non-diagnostics) pages display correctly, I am assuming the diagnostics display code is to blame.
What would cause this?

Thanks!

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  Cody J.

  NHD Staff

  • June 03, 2022 13:47

  Hello Guy,

  It is possible there is an interface timing issue occurring.

  However, it is tough to dig deeper into the problem without knowing more details about the software driving the display.

  Are the incorrect characters/artifacts always the same on the diagnostics page or do they change every time the page is displayed?

  Best Regards,

  Cody J.

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  Guy St-Denis

  • June 03, 2022 14:14

  I compared a series of photos of the pages taken today with a series taken May 30, and they are identical. So as far as I can tell, the behaviour is consistent.
  I'm not expecting a fix for this as I suspect it is caused by how the diagnostics display code was written,,, and I can't (easily) update the firmware.

  I guess I was just curious to understand how the display code could produce these different results on 2 different displays. And how to avoid writing such code...

  Thanks!

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  Guy St-Denis

  • June 03, 2022 14:16

  The artifacts often seem to appear in pairs, with the second character being '0'... maybe that is a clue.

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  Cody J.

  NHD Staff

  • June 03, 2022 15:03

  Hello Guy,

  My best guess, since it is difficult to access the firmware, is that the diagnostics page is using byte codes that may be invisible on the old display, but are visible on the new display. These byte codes could be related to functions unique to the controller IC on the old display. 

  If possible, it may be worthwhile to dig into the old display's controller IC spec sheet and look to see if any commands correspond with some of the artifact character's ASCII code.

  Best Regards,

  Cody J.

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  Guy St-Denis

  • June 03, 2022 15:06

  Thanks for your help Cody!

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