HP-71B ver 2CCCC - Anyone ever have one?

[MikeSD]

Years ago, I came across a version 2CCCC. It was the only one I ever saw. And I've owned hundreds of 71B. It was mint condition. But a few minutes after I discovered it was a 2CCCC version, it died. I opened it up and the zebra strip was toast.

Because of the physical condition, I decided against wiring it directly. I thought, maybe I'll find a crappy 71B plastic back that I could slavage the zerbra strip.

But in the intervening years, I lost track of which top half was the 2CCCC. I still have 2 top halves in mint or near mint condition. And a couple of bottom halves. Not sure which goes to which. And apparently, at some point I did some soldering to the zebra connector.

Maybe it's time to go back and try and get these working.

Questions:
1) Is there a way to identify a 2CCCC version by visual inspection? The serial number is on the bottom half, so if the version goes with the top half, the serial number won't help. But it might tell me which bottom half to use.
2) Is the version related to the top half, or bottom half, or both?
3) Can the 2CCCC version be used with any plastic half bottom?
4) Will solder on the zebra strip connector, affect the connection, if I do find a zebra strip?
5) Is there a listing of the pinouts for the zebra strip connector?

I do, now, have a 2CDCC 71B, with mushy key. But I'm leary about opening it to check the zebra strip. I don't want to wind up with 2 non-working 71B

[Dave Frederickson]

Hi Mike,

First of all, the top half only has the display chips and CPU. The ROM and RAM are on the bottom half with the serial number.

Answers:
1. My info shows versions 2CCCC on units with date codes 2713A to 2745A but the range could be wider.
2. Just the bottom half.
3. N/A
4. Removing all the solder can be tricky. Then your left with the issue of dissimilar metal corrosion. I'd recommend against it.
5. Using an ohm meter and referring to the Hardware IDS it shouldn't be too much trouble to figure out.

Dave

[MikeSD]

(12-20-2023 08:05 PM)Dave Frederickson Wrote:  Hi Mike,

First of all, the top half only has the display chips and CPU. The ROM and RAM are on the bottom half with the serial number.

Answers:
1. My info shows versions 2CCCC on units with date codes 2713A to 2745A but the range could be wider.
2. Just the bottom half.
3. N/A
4. Removing all the solder can be tricky. Then your left with the issue of dissimilar metal corrosion. I'd recommend against it.
5. Using an ohm meter and referring to the Hardware IDS it shouldn't be too much trouble to figure out.

Dave

Thanks for the info. I should be able to find the correct bottom half, that has 2CCCC in it.

I also have a short 24 pin flex cable that has almost the exact spacing. I can get 4 flat traces soldered to 4 contacts without touching the other pads. Every 5th position won't line up. So, I'll just snip off every 5th trace. And use the four 4 trace sections and remove the 5th and by splitting it up the cable a bit, have enough flexibility to attach the other traces. But it might be nicer looking if I just split the flex circuit into 4 distinct flex circuits.

0 0 0 0 X 0 0 0 0 X 0 0 0 0 X 0 0 0 0 X X X X X

0 - Conected trace
X - Discarded trace

Thanks, if it's successful, I'll post a picture.

[Garth Wilson]

Note:  Those are not zebra strips.  This post
https://www.hpmuseum.org/forum/thread-18...#pid161277
shows what zebra strips are.

[Dave Frederickson]

(12-20-2023 10:17 PM)Garth Wilson Wrote:  Note:  Those are not zebra strips. 

True. In actuality they're more like the Fujipoly Gold 8000 elastomeric connectors.
https://www.fujipoly.com/usa/products/ze...ctors.html

In any case, I knew which PCB contacts Dan was referring to and my answer remains unchanged.

BTW, I call them "golden zebras" to distinguish them from the conductive rubber strips commonly called zebra connectors.

[Raymond Del Tondo]

(12-21-2023 12:07 AM)Dave Frederickson Wrote:  

(12-20-2023 10:17 PM)Garth Wilson Wrote:  Note:  Those are not zebra strips.

True. In actuality they're more like the Fujipoly Gold 8000 elastomeric connectors.
https://www.fujipoly.com/usa/products/ze...ctors.html
In any case, I knew which PCB contacts Dan was referring to and my answer remains unchanged.
BTW, I call them "golden zebras" to distinguish them from the conductive rubber strips commonly called zebra connectors.

On the Fujipoly website they are actually sorted in "Product Lines » ZEBRA Elastomeric Connectors » Gold 8000 Connectors" .
And the first words in the first paragraph say "The FUJIPOLY ZEBRA® Series 8000 elastomeric connector elements are D-shaped",
so I think the old Zebra strips could be called "Rubber Zebras" to distinguish them from the "Golden Zebras";-)

[MikeSD]

(12-20-2023 10:17 PM)Garth Wilson Wrote:  Note:  Those are not zebra strips.  This post
https://www.hpmuseum.org/forum/thread-18...#pid161277
shows what zebra strips are.

Not sure who you are addressing this too, but I know what a zebra strip is. I was just using a flex cable because I don't have any zebra strips.

Dave,

Regarding the date code, I may have misplaced my 2CCCC bottom half. Mine are in the 2813A range. Still, it's worth getting my 2 nice top halves working.