My 83+SE acted up the last time I went to use it after not touching it for about a month and using it every few months regularly before that.

What its doing:
- Not turning on or showing any activity

- If it does turn on, its not a fully black screen, but it is not random and looks the same each time. Pressing other buttons in this state has no effect (e.g. CLEAR, typing numbers and operators, etc., does not affect what is displayed on the screen in any way), however I can turn it off with 2nd+ON. So I have the impression that this isn't an issue with the screen or ribbon cable. (I'll try and get a photo of this, but I've not been able to get it turned on again in the last hour or so).


What I've done so far:
- Pulled all batteries, waited a few minutes and attempted a RAM clear (batteries all new and also measured to be in good voltage even under load)

- Opened the calculator and cleaned off all contacts used for battery connection (the pads for the main batteries were worn through, the pad for the backup battery was heavily worn but still making contact).

- Quick visual inspection of the PCB for any corrosion, damage, etc.


Odd things:
- If I can get it to turn on and show the aforementioned pattern on screen, I can turn it off and back on all day long. If I remove a main battery, wait a moment, put the battery back in, there is a good chance it will no longer turn on any longer. Sometimes if I leave a battery out for 10+ minutes and put it back in can I get it back in to a state where it is turning on and off again.


I've not yet done a detailed inspection of any of the solder joints or measured the LCD ribbon cable continuity; I'll do that when I have time and update the thread when I do.


Thanks in advance for any next debugging steps that you can recommend.
This sounds like classic coarse ribbon cable failure, unfortunately: https://www.cemetech.net/forum/viewtopic.php?t=5161 . Have you tried connecting to it with your linking software of choice when you expect it to be on (even if the screen isn't showing anything)?
Well, I've got good news and bad news.

I was able to connect with TI connect (thank you for that suggestion, its been probably close to a decade since I last used TI connect and completely forgot about it), I was able to get data, screenshots, etc., all while the display was blank.



The screenshot I could get though, was not good.



That is similar to, but not exactly the same pattern that gets displayed on screen when I do get screen activity.

I still am unsure if this is an LCD cable issue causing there to be nothing displayed on the real screen as there is something else going on as well. I can certainly do a deeper inspection of the PCB and solder joints to see if anything else is out of the ordinary. But I'd still like to hear some ideas from people who have spent more time inside these devices than I have before I go poking around.
This is absolutely coarse ribbon cable failure, because the screenshot is read back over the same cable from the LCD's RAM. You'll need to do a partial or full replacement of that cable.
KermMartian wrote:
This is absolutely coarse ribbon cable failure, because the screenshot is read back over the same cable from the LCD's RAM. You'll need to do a partial or full replacement of that cable.


Okay, that is a detail I was unaware of. Seems silly that the LCDs buffer is used for displaying screen shots like that rather than actual RAM. Thank you for the info, I'll get to replacing the cable shortly.

I don't suppose anyone makes an off the shelf flex cable that can be soldered right in place, as opposed to having to tack individual wires for a full or partial replacement?
I'm not aware of anyone using such a cable, although plenty of ribbon cables of various types exist. If you were to explore some options, I'm sure the community would be pleased to learn from your exploration!

The LCD buffer is read for screenshots because the OS doesn't always use a buffer in RAM to construct the contents of the LCD ahead of time, and sometimes instead writes directly to the LCD. For example, graph cursors can be drawn directly to the LCD, and erased by writing to the LCD from a RAM buffer, rather than needing to go through the slower and more complex operation of copying a section of a RAM buffer elsewhere, drawing the cursor to that buffer, copying all of or part of the buffer to the LCD, then erasing the cursor by copying the saved section of RAM back to the main buffer and again copying all or part of the buffer to the LCD.
  
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