Replaced the display in a 15c - comments and quesitons

[vaklaff]

Hello

The old 15c that's permanently on my desk was hit by a display bleed. Although very slow - maybe 5 years of progress and still not reaching any segment, I decided to try to replace the display. A couple of days ago I bought a cheap and beaten 12c of similar vintage. For the record, it's the second generation Voyager per the informal classification created by Randy Sloyer in this thread. (Randy, wherever you are, thanks! It was not the first time I learned from you.)

I spent today's rainy afternoon on it. Disassembled both the calculators, shaved the heat stakes, removed the displays, cleaned the contacts, put the 12c's display on the 15c's board. Easy enough, except some segment didn't catch up. On closer inspections, one zebra of the 12c was deformed so I replaced it with one taken from the bad display. Now the display worked flawlessly.

OK, I cleaned everything I could, the board, keys, rubber pad and so on and so forth and assembled everything back. The absolutely worst part was, as expected, the heat stakes. Using a pointy soldering iron, I first melted the remnants of the stakes. That created a basic "grip" on the board. Then I tried to strengthen them by adding the original shavings. That was very slow and very messy job. This is the results:

(The old leaking display is on the picture as well)

Despite the mess, the keyboard feels firm, well supported, with uniform action, passes the test:
.
Still I'm considering putting a sheet of foam between the board and the case. First, to minimize possible movements, second, to keep the improvized "heads" in place, in case they break off. I sure don't want them to wander around, eventually ending up in the keyboard or the display. Unfortunately I cannot find a suitable foam at home right now.

For the sake of completeness, the display test:

It's sort of a success but nobody should look inside!

Anyway. I was impressed by the looks of the internals. Exactly 40 years old but seemed like made yesterday. A beautiful piece of technology. Until I laid my hands on it, that is :-)

When I was washing the keys, they resembled some other model's keys that I washed some time ago, maybe the 65? It was more than "resembled", it felt like rewinding my memory. Is it possible that HP was using the very same shape and size of the keys for several generations? Just curious, not that's important.

What I really need to ask are these questions:

I forgot to put back the see-through plastic flap that partly covers the battery compartment. What's its purpose? Now it's too late to anchor it below the board but if the flap is important I'll think something up.

Also, there was a strip of adhesive tape on the lowest part of the board. Actually, adhesive it was no more and I didn't put it back. Again, what was it for?

Thanks!

[AnnoyedOne]

(09-14-2024 05:37 PM)vaklaff Wrote:  The old 15c that's permanently on my desk was hit by a display bleed.

The HP-16C I bought in 1985 also has "LCD bleed" and has for a decades. It never affected anything so I never worried about it.

My HP-15C CE has a 16C mode so I'll leave the HP-16C alone.

Nice to know that it can be repaired though.

(09-14-2024 05:37 PM)vaklaff Wrote:  I forgot to put back the see-through plastic flap that partly covers the battery compartment. What's its purpose?

Also, there was a strip of adhesive tape on the lowest part of the board. Actually, adhesive it was no more and didn't put it back. Again, what was it for?

I think the plastic flap helps secure the three LR44 batteries. As for the adhesive I don't know.

A1

[Steve Simpkin]

For reference, here is Charles McCord giving a presentation at HPCC 2022 where he describes the Voyager redesign process to use a single circuit board.
https://www.youtube.com/watch?v=_vs7wFW0SG4

[AnnoyedOne]

(09-14-2024 06:48 PM)Steve Simpkin Wrote:  For reference, here is Charles McCord giving a presentation at HPCC 2022 where he describes the Voyager redesign process to use a single circuit board.

The SST chip (and hence PCB).

Thanks for posting that presentation video link. "Very interesting" (now where is that from? )

So my HP-15C purchased in March, 1982 is pre-SST. I didn't know that. However my mid 1985 HP-16C is post-SST! Both made at HP Corvalis though.

Plus the original HP-12C had a "comma bug" long before 2023! Start at 21:50 in the video.

More on the HP-12C starting at 28:20.

A1

[brouhaha]

(09-16-2024 07:07 PM)AnnoyedOne Wrote:  However my mid 1985 HP-16C is post-SST! Both made at HP Corvalis though.

I haven't seen an SST 16C anywhere near that early. I don' t think I've seen any SST Voyager calcs before 1988. What is the part number on the chip? Should be 1LQ9-03nn, but I don't know what the nn would be.

I don't have the 1LH1-03nn part number for the last pre-SST version, either. I would have expected a mid-85 16C to have that and the 1LM2-0001 Nut CPU chip.

[vaklaff]

(09-17-2024 07:06 AM)brouhaha Wrote:  I haven't seen an SST 16C anywhere near that early. I don' t think I've seen any SST Voyager calcs before 1988.

Is the 15c pictured at the beginning of this thread is an SST one?

[AnnoyedOne]

(09-17-2024 07:06 AM)brouhaha Wrote:  What is the part number on the chip?

I've no idea. Its been decades since I took the back off my 16C and no photos.

I was going off what Charles McCord said in the video about the SST chip being from the "1983 timeframe" Voyagers (video @20:20). "3" and "8" look similar so maybe a mistake from printed documents.

A1

[AnnoyedOne]

(09-17-2024 11:52 AM)vaklaff Wrote:  Is the 15c pictured at the beginning of this thread is an SST one?

Based on the video SST based 15C's have two chips, Yours has three. Pre-SST probably.

   
SST 15C (from the video)

The other early Voyager models have one (SST) chip according to Charles McCord.

A1

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

PPS: From your first posted photo the 15C uses a 1LF5-0301 CPU which is a 1st/2nd generation design. The chip has a 84223 date code so it was made week 22/23 of 1984. The PCB has a 00015-80001 part number though.