HP 38C calculator disassembly?

[Peabody]

Has anyone here ever taken apart one of these calculators? My "6"
key is not registering all the time, and I thought I might be able
to clean out the crud in there and make it work again. But it's not
obvious how one would take one of these apart. I've Googled, but
haven't found anything. If anyone has a relevant link, I would
appreciate it.

FWIW, I still think these HPs are wonderful. RPN forever! We don't
need no stinkin "=" key.

 

[William Sommerwerck]

Does the calculator have rubber feet on the back? There are often screws
under the feet.

I had one of the original HP-35s (1972). I'd never heard of RPN, and thought
"What's going on here?" After a few minutes using the calculator, I was
permanently converted. Why would anyone use algebraic entry?

 

[propman]

Has anyone here ever taken apart one of these calculators? My "6"
key is not registering all the time, and I thought I might be able
to clean out the crud in there and make it work again. But it's not
obvious how one would take one of these apart. I've Googled, but
haven't found anything. If anyone has a relevant link, I would
appreciate it.

FWIW, I still think these HPs are wonderful. RPN forever! We don't
need no stinkin "=" key.

don't see anything specific re: 38c at the following site but it might
give you an idea on how to proceed:


http://www.hpmuseum.org/disasm.htm

 

[Charles]

Does the calculator have rubber feet on the back? There are often screws
under the feet.

I had one of the original HP-35s (1972). I'd never heard of RPN, and
thought
"What's going on here?" After a few minutes using the calculator, I was
permanently converted. Why would anyone use algebraic entry?

Reverse Polish Notation ... was judged as a racial slur when HP first hit
the market ;>)

Seriously, I was amazed at how easy it was to learn and how many keystrokes
it saved with chain calculations. I am retired and have lost track of RPN
.... is it available in modern calculators?

 

[William Sommerwerck]

I am retired and have lost track of RPN

... is it available in modern calculators?

HP still sells calculators with RPN. These sometimes include algebraic
notation to simplify the entry of formulas when programming.

It should be noted that almost all "algebraic" calculators are hybrid,
mixing RPN with algebraic entry.

 

[iws]

|snip

| FWIW, I still think these HPs are wonderful. RPN forever! We don't
| need no stinkin "=" key.

Ah yes, RPN vs. algebraic. Kinda the Mac vs PC wars of the 1970's. Or the
Betamax vs. VHS wars of the 1980's.

 

[Reinhard Zwirner]

[...]
The HP35s has both Enter and "=" keys (although the "=" key is
somewhat hidden). ^^ ^^

Hi Jeff

Where? I bought my HP35 in 1974 and haven't found this key till now!

Very interested

Reinhard

 

[William Sommerwerck]

The HP35s has both Enter and "=" keys (although the "=" key

Where? I bought my HP35 in 1974 and haven't found this key till now!

He should have said HP-35S. See above.

 

[Reinhard Zwirner]

[...]
The HP35s has both Enter and "=" keys (although the "=" key is
somewhat hidden). ^^ ^^

Hi Jeff

Where? I bought my HP35 in 1974 and haven't found this key till now!

HP35s != HP35

Many thanks to you and William! I did misinterpret the s as a plural s.
Now I know that there is a HP 35 revival calculator ;-) ...

Best regards

Reinhard

 

[Peabody]

Jeff Liebermann says...

You're going to have a problem getting the keyboard
section apart. The case comes off easily. Two screws in
the battery compartment and it breaks open. Watch out
for the loose IC's. Take photos if you can't remember
the chip directions.

The keyboard is held together by melted plastic blobs.
Break them off and the keyboard section will come apart,
but good luck getting it back together. You're better
off immersing the entire assembled keyboard in some
alcohol, and hope that the crud will wash away.
Eventually, the alcohol (and water) will evaporate.

I think you are describing the early version of the 38C,
and perhaps other Spice series calculators. At some point HP
switched over to a new design which had all the chips
soldered in the usual way. And that's what I have.

I didn't find the case to come apart easily at all. I ended
up using the dental floss method of getting it apart. That's
from the hpmuseum.org forum. The keyboard on mine has a
metal dome for each key, and all the domes are held in the
right place by a sheet of plastic tape. So I cut through
the tape around the misfiring dome and removed it, cleaned
it, and put it back. It seems to work fine now.

I took pictures of the keyboard and the bottom latch:

http://drop.io/HP38C_KeyRepair

 

[Peabody]

Jeff Liebermann says...

Your HP38c and my HP38e are quite different.

Yes, a completely different design. The early 38Cs were like yours
too.

Now to get it back together...

Well, it may be 25 years old, but I still love this
calculator. And I didn't see any on Ebay. That's a bad
sign I think.

 

[Bob Larter]

Sigh. Time to tear one apart. I couldn't find an HP38c in my pile,
but did find three HP38e calculators. I tore one apart and tooks some
photos:
<http://www.11junk.com/pics/hp38e/>
Note that the chips are NOT soldered.

Holy shit! Until I looked at your photo, I thought that you meant that
the legs had corroded, or that the chips were socketed, or something
like that. I'm amazed that they were that cheap when they were
manufacturing them, or that they've lasted so long!