HP 15C Issue with screen refresh

[jhlee0218]

Hi All,

This is my second post.
So, I recently acquired two voyagers (11C and 15C). While they are both in a good condition cosmetically, both of them are exhibiting this problem that I did not notice with my other voyager models (another 15C and 12C).

What happens is when the contents of the display change, sometimes there is a noticeable lag with some segments of the display.
For instance, if I have 1234567890 on the stack, and press CLEAR (<-) key, it does not display 0.000000000 immediately, but there is some delay and it appears as if some residue of the previous entry appears briefly.
Another instance this can be easily observed is when I am navigating through the program steps.

I recorded a video using slo-mo mode of my phone. Here is the link:
https://www.dropbox.com/s/a49pa17hbvapl8...M.mov?dl=0

Do you have any experience with this symptom and what might be causing it (and how to improve it)?

I thought it may be caused by the calculator not being used for so long. I wrote a program that repeatedly shows different numbers and ran it for a few hours, but it did not do anything.

[damaltor]

My 15c both do that, too. i am not concerned.

[jhlee0218]

(04-09-2021 06:24 AM)damaltor Wrote:  My 15c both do that, too. i am not concerned.

Thank you for the information! It is quite relieving to know. I was debating with myself whether I should get a third 15C in a hope of getting one without this issue.

Since many samples apparently behave this way, I guess buying another one is probably pointless. I wonder, though.. Can you have too many 15C's?

[damaltor]

Of course not

Also, after thinking about your question for a while, I remembered this article mentioning 2:1 multiplexing in some displays vs 4:1 multiplexing in other variants. That might have something to do with it - you might be able to deduce that from the serial numbers in the article.

http://www.brouhaha.com/~eric/hpcalc/voy...iants.html

These two display driving methods have their pros and cons - 2:1 has a minimal better contrast and less ghosting, while 4:1 needs less pins on the display driver. If I remember correctly, later models used 4:1 and are therefore more susceptible to ghosting.