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HP Forum Archive 10

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"Hybrid"HP15C lives and Rebuildin HP41broken posts
Message #1 Posted by Vieira, Luiz C. (Brazil) on 19 Jan 2003, 3:02 a.m.


for those who remembered, I posted a few months ago a (some) question(s) about the ID codes for the chips used in two different HP15C's. At that time I had a broken HP11C that came back to life after being disassembled.

Well, I devoted this Saturday to the task, and I must tell you that the "hybrid" HP15C IS working, and is uses the following chips:

1LE2-0321 (RAM/ROM Display Driver, or R2D2)
1LH1-0302 (64 registers RAM and extra ROM)
1LM2-0001 (this is the original HP11C's KBD scanner, replacing the 1LE5-0301)

The last IC in the list is the one that was not supposed to be there. I posted the "correct" list for some Voyagers (except the HP10C that I do not have) about three to four months ago, but I did not stop to search for it.

After soldering the last terminal of the last chip I placed the LCD without much care and turned the calcualtor ON. A weak Pr Error was very welcome, and I slightly pressed the LCD's metal frame so I could see it better. Crystal clear! After testing a few features, I decided to "order" the [ON][] test and. Everything fine EXCEPT for the PRGM annunciator and the "d" segment of the rightmost digit, that kept off. I slightly pressed the LCD's frame again but no results. OK, let's rebuild it.

I'm haveing a hard time with the LCD since then, because I reassembled it about four times and it comes better and worst, out of alignment. Sometimes some digits are not lit, sometimes only a few segments. What bothers me is that the first time I was lazy and it worked a lot better, only two segments did not turn ON. If it was BEGIN, or D.MY I would not care about it. But PRGM and one segment were enough to ask me for the disassembling.

If someone has any tip other then "Never disassembled the LCD's frame" I'm thanked. I decided to disassemble it because I'b be removing and soldering components right "under" it and I was affraid of cracking it (preassure, temperature, fall). It is intact, but failling.

As soon as I get it in place and working, I'm scanning the keyboard and sending the image to those who want.

About the HP41 broken posts' photos: they are the sadest expression from someone that was not born to hold a photographic camera. At least three of them and part of a fourth picture will be enough to see the begining and the end of the task. I'll add the needing draws to "visualize" the mid steps so the ones who need to do it will not have difficulties understanding the process.

Best regards.

"Hybrid" HP15C fully operative!
Message #2 Posted by Vieira, Luiz C. (Brazil) on 19 Jan 2003, 2:47 p.m.,
in response to message #1 by Vieira, Luiz C. (Brazil)


the HP15C described in the first post of this thread is now working alright. The problem was not the alignment. The fact is that I have saved the LCD polymers and did not check them prior to mounting. One of them was dirty and a bad contact was enough. I did not notice because the dirty was visible only in certain viewing angles. I cleand both plymers carefully and it's fine, now.

For those who were expecting to know about the chipset "blend", excuse-me taking so long to get this subject back, because I did not want to loose the HP11C without knowing if the HP15C chipset was working fine. At the moment I decided to do the "transplantation" about two to three months ago, the HP11C was not working. And the task demanded full attention and dedication... and also a bit of "inspiration"!

Now I'm going to another step: reassembling the HP15C's keyboard. But that's another story...

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