HP-71B problem has me stumped

[Mike]

I know a bit about the 71B but I have two that have me stumped. I have a dead mint 2CCCC 71B that was working, then became kind of intermittent, and then just stopped working all together.

When I say intermittent, I mean it would work and then if moved would shut off. Movement seemed to be the problem. Or bad connection type problem. I could tap the 71B and it would come back on. Now it doesn't come on at all. At first I thought it was the connector between the two halves. But I swapped that connector with another unit and it didn't fix the problem. I have also swapped the back half and the problem isn't with that half.

Now, I find that I have another mint 71B that had exactly the same behavior. Was working and then suddenly stopped the same way. I'm stumped.

I wouldn't mind so much, if this were not happening to mint 71Bs.

The problem is kind of hard to find because these are the plastic back, you can't test them when opened. Maybe I need to fabricate some sort of flexible cable to allow it to be opened and still function. Anyway, I was wondering if anyone knows of some common failure of these plastic back 71B?

Edited: 1 Nov 2006, 4:23 p.m.

[Vassilis Prevelakis]

This behavior suggests either a cracked trace or a cold solder joint (of course it could well be a problem with that infernal strip linking the two halves).

I assume you have already tried the test with some sort of constant pressure pushing the two parts together (without touching any keys of course). This would rule out the strip.

I wonder how HP tested these models (as you say, you can't operate them disassembled). Some kind of 71 case with holes (ala the HP-41 service setup).

**vp

[Antonio Maschio (Italy)]

infernal seems too much! (in Italian, it means "from hell")

But I know you meant "internal"!

-- Antonio

[Vassilis Prevelakis]

Antonio Maschio wrote:

> infernal seems too much! (in Italian, it means "from hell")

>

> But I know you meant "internal"!

No, I meant infernal. And if you had to replace this strip by soldering little wires across the two boards, you'd agree with me :-)

**vp

[Mike]

Funny how both words work. :-)

I may have to try though. I sure hate to have a non-working mint condition 2CCCC 71B. Of course I'd have to do it on the ends, very gently, so as not to make the connector non-functional. If I do it and it is the source of the problem, then I could just find a new strip. However, I really don't think this is the problem. I just have to prove it to myself.

Edited: 3 Nov 2006, 5:16 p.m.

[Vassilis Prevelakis]

Mike wrote:

> Funny how both words work. :-)

This reminds me of this outfit:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140052886695

whre they say:

Quote:

---

LOCAL PICK-UP:
NONE. We have decided to scale back to selling part time and no longer have the time ( and patients ) to wait around for pick-ups, [...]

---

(my emphasis)

I can just visualize a patient with an IV drip on a portable stand waiting outside the warehouse for a customer pickup :-)

**vp

[Etienne Victoria]

Hello Mike, all!

The Hp-71B zebra strip can suffer mechanical and/or oxydization damage.

I only know 2 ways to repair it :

1- Solder the 17 contacts board to board with wrapping wire (0,25 mm) as shown here:

and detailed here.

2- Or restore the strip by gluing 17 thin unisulated copper wires in the strip plastic piece. This is somewhat less reliable but preserves the original internal aspect.

To show procedure 2, I'll have to open one of my previously restored 71Bs...just let me know if somebody is interested.

Cheers from France!

Etienne

Edited: 4 Nov 2006, 3:15 p.m.

[Vassilis Prevelakis]

Wow! Great pictures.

I thought I was the only one crazy enough to try to fix an HP-71B this way :-)

In my case the fix did not work, so I packed the calculator away, until about a year ago when I came across it accidentally, so I gave it another look and this time I saw that one solder blob was actually touching the next one. Once I fixed that, the HP-71B came back to life and has been working ever since. Its the one I use more often because its the one I brought back to life.

**vp

[Eric Smith]

Quote:

---

Its the one I use more often because its the one I brought back to life.

---

Somehow reminds me of badly translated Coca-Cola advertisements in China. The claim (possibly an urban legend, though it isn't listed on snopes.com) is that the "Coke Adds Life" slogan was translated as "Coke Brings Your Ancestors Back From the Dead".

Given how careful the Coca-Cola Company was at avoiding a bad phonetic translation of their name (e.g., the urban legend about it being "Bite the Wax Tadpole"), it seems unlikely that they would screw up their slogan.

If a bit of soldering brings an HP-71B back from the dead, I'm all for it, regardless of what beverage you like. :-)

[Mikecimerian]

This isn't an urban legend. It goes back to first experiments in computer translation.

The experiment translated "Cokes brings life" to Mandarin and they used the same program to translate the output back to English.

It came back as : "Coke brings your ancestors back from the grave"

The same experiment was done in English-Russian-English with the following sentence : "The flesh may be weak but the Spirit is strong"

It came back as ; "The meat has spoiled and the vodka is strong"

I would appreciate getting a peek on the source code.

[Ed Look]

They may have discovered a machine that does not run by conducting electrons, holes, protons, nor even photons; they may have discovered the first one that runs on ethanol conduction.

The bad news is they probably found a few electrons in the alcohol stream... :p

[Valentin Albillo]

Try to translate forth and back to some other language the following sentences:

- Time flies like an arrow (and Fruit flies like a banana)

- I saw that gasoline can explode

Best regards from V.

[Mike]

I'm not sure the zebra strip is the problem but I was going to try soldering wires to the ends of the connectors to be sure.

However, today I turned it on, and it works again. Really wierd! I know for a fact that it's not the battery contacts. I have swapped the entire back and that didn't fix the problem and I used a good zebra strip and that didn't fix it. When I move the good zebra strip from 71b to 71b it always works so I know that isn't the problem (99.9% :-)

But for some reason, today it works. I just wish my 2CCCC version would magically start working.

:-)

Thanks