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Hp-70 incorrect key registering
03-19-2016, 01:23 AM
Post: #1
Hp-70 incorrect key registering
I am trying to fix a HP-70 for a fellow enthusiast. The symptoms are:
Several keys such as /, O and . Do not register correctly. For example the decimal key is interpreted as the change sign key.

To rule out corrosion or something else on the keyboard, I paired up a 45 motherboard to the keyboard. With this combo it works as it should.

So, this leads me to conclude it is the 70 motherboard. But what chip has failed? A common one or one unique to the 70?
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03-19-2016, 02:00 AM (This post was last modified: 03-19-2016 02:00 AM by Geoff Quickfall.)
Post: #2
RE: Hp-70 incorrect key registering
Check out this posting, mine is now running perfectly:

http://www.hpmuseum.org/forum/thread-4989.html

Geoff
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03-19-2016, 02:20 AM (This post was last modified: 03-19-2016 12:40 PM by aj04062.)
Post: #3
RE: Hp-70 incorrect key registering
That doesn't line up with this units malfunction. It's as if it is interpreting the wrong row and columns.
Divide = Add
zero = TBD
decimal = CHS
CLX = M+

You can see I almost have a row to row confusion here, but not quite. BTW, the row with enter CHS and M+ work fine.

Would that likely be a failing CTC Chip?
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03-19-2016, 07:13 PM
Post: #4
RE: Hp-70 incorrect key registering
No, not a ram problem, just lots of info on the chip set.

How about corrosion on the motherboard?

How did the 70 mother board work in the 45 keyboard?

Inspect the mother board, especially around the chip set solder points and traces. Resolder the chip set especially around the ROMs. A motherboard wash/rinse with warm vinegar followed by water then anhydrous alcohol. Inspect the traces. Test when dry.

Geoff
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03-19-2016, 07:27 PM
Post: #5
RE: Hp-70 incorrect key registering
I cannot see any corrosion on the motherboard.

I did not swap the other way.

I'll give the 70 board a vinegar bath. Thanks!
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03-19-2016, 08:45 PM
Post: #6
RE: Hp-70 incorrect key registering
Just ruling out mechanical issues before diving into the ARC chip.

Cheers, Geoff.
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03-27-2016, 12:01 PM
Post: #7
RE: Hp-70 incorrect key registering
I have cleaned and re-flowed solder with no luck.

Is the only source of this behavior the CTC or could ROM cause this too?
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04-10-2016, 02:50 AM
Post: #8
RE: Hp-70 incorrect key registering
Update: a successful transplant of a good CTC chip has cured this 70 of its issues
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04-10-2016, 03:19 AM
Post: #9
RE: Hp-70 incorrect key registering
It's good to hear that, another saved classic!

-katie

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04-10-2016, 06:09 AM
Post: #10
RE: Hp-70 incorrect key registering
Indeed.

Salute !!!

2speed HP41CX,int2XMEM+ZEN, HPIL+DEVEL, HPIL+X/IO, I/R, 82143, 82163, 82162 -25,35,45,55,65,67,70,80
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04-10-2016, 05:21 PM
Post: #11
RE: Hp-70 incorrect key registering
Excellent.
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04-10-2016, 05:40 PM (This post was last modified: 04-10-2016 05:41 PM by Massimo Gnerucci.)
Post: #12
RE: Hp-70 incorrect key registering
(04-10-2016 05:21 PM)Geoff Quickfall Wrote:  Excellent.

(04-10-2016 05:25 PM)Geoff Quickfall Wrote:  Excellent.

Incorrect key registering for you too?

Smile Big Grin

Greetings,
    Massimo

-+×÷ ↔ left is right and right is wrong
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04-11-2016, 12:45 AM (This post was last modified: 04-11-2016 12:48 AM by Geoff Quickfall.)
Post: #13
RE: Hp-70 incorrect key registering
Ha,

No idea why the double. Maybe virtual key bounce :-)

For continuities sake, Massimo is referring to a double post, the second of which I have deleted.
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04-11-2016, 03:23 AM
Post: #14
RE: Hp-70 incorrect key registering
LOL !!

Always appreciate the humor, and a successful repair of a classic calculator is certainly cause for celebration and levity.

2speed HP41CX,int2XMEM+ZEN, HPIL+DEVEL, HPIL+X/IO, I/R, 82143, 82163, 82162 -25,35,45,55,65,67,70,80
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