HELLP! HP-34C HELLP! Plastic case problem


I NEED HELP !! HP-34C !!

How do you get the &&^%$&%^# plastic case opened up?

I have got a specimen in my hands. Wonderful thing, which I have much familiarity from its original heydey around 1978 - 1984 .

I got a specimen thru an internet purchase. It's in
great shape, BUT, it has the same problem I experienced with my own unit back in 1984.

Some ^%$@#%^$#%$ HP designer back in 1977 did NOT do his job. An act of pure maliciousness, you CAN'T get this case
apart without damaging it. BUT, I need to get the case apart WITHOUT DAMAGING IT !!!

Sure, take out the 2 screws, try to lift the back off,
but no way. It's stuck together almost like glue down
by the "Hewlett Packard HP-34C" logo at the lower edge.

Instead of giving it 2 pleasant pins that could be removed,
that turkey whose name I already mentioned (^%$@#%^$#%$) made the thing incomprehensible and easily damaged.

I can already see some minor damage on this unit's plastic due to somebody trying to get it open (for justified or
unjustified reasons, it seems to work fine).

I AM SURE THAT there must be some valid trick to get it open. Surely HP service did not destroy each plastic
case that came back to them?

Its amazing how a design engineer who does a fine job disappears into the woodwork and nobody ever knows who he is or what he did. But some turkey who is nothing more than a vandal on a timeclock, you can remember his name 30 years after he worked in the plastics department. His name is ^%$@#%^$#%$

Thanks in advance for somebody explaining the magic 'flick of the wrist that will get this thing opened up so I can
repair the plastic that somebody already had messed with.

What's hilarious is I felt a need to open mine up back
around '84 and had identical pry-marks and identical types
of damage, and now I get some completely unrelated unit from somebody else many states away, and see the same thing.
Can see the 'Dilbert' design manager now...... Excellent work Mr. ^%$@#%^$#%$ I am really impressed with your plastic case design, I'm going to promote you to MANAGEMENT.



there is an interlock assembly that is easy to be removed if you "dp the trick".

If you look at the back "glued" (not glued, in fact) bottom side, you'll see there is a small plastic "slice" in the keyboard half rounding around the back half of the calculator case. You shoud be able to slide the back half "over" this plastic slice, by gently twisting and smoothly spinning the back half, and then moving it out of the upper (keyboard) half. I once read that using dental floss is safe and helpfull... no, not exactly in your tooth, around between both halves. I remember this technique was described some time ago, but I did not try it. Please, have a look at the image below and you'll have an idea: it's a "free-mouse", not scaled, far-from-actual-object drawing represent a cut-view. Shaded half is the "bottom" half, as if it is upside-down.

You may notice the "small slice" at the righ side of the drawing.

Hope this helps you to find the best way to "separate" them.

Best regards.

Luiz C. Vieira - Brazil


and it's all happy camper again.

Here's my ten cents worth of wisdom:

I used a little cleaner-degreaser on the
slide switches, which of course leaves them 'dry'. Before reassembling, I added just a touch of "tri-flow" which is similar to a WD-40 product with white-powder teflon particles added. After the oils dissipate, the teflon
remains in the metal pores. So that's what I did.


I trimmed a little plastic away (5 thousandths,
ten thousandths) so that maybe it would
come apart easier in future. Visualize as follows:
You get the back off finally (and could well be
only with damaging something, but I did OK). Now,
set the calculator aside but hang onto that back.
Get your X-acto knife. I can't hardly say it with words,
but remove a little plastic (and/or 45 degree it)
at the very edge of the protruding 'clip' and
also, trim a little at the very bottom edge of the case.

Two places to trim, just along the bottom edge,
just 5 or 10 thousandths. I'm sure it will help
in future.

THANKS AGAIN! Awesome diagram!


OK this baby is up and running. THIS IS MY FIRST TIME

Early version with unsoldered chips inside is unreliable?
I dunno, thats what it is, and its working OK.
I like the extra 1.5 ounces of weight.

*CLICK*. Not like a 32S where they were too stinkin'
cheap to give you a power switch.

What is wrong with that Carly creature, parading
around about "cost reduction". I can see her now
in the boardroom, with a 50 foot long Mahogany
table and a $3000 "power suit" that she's wearing,
leather chairs all around, parading about her "cost reduction" and the need to boost profits? That
we don't even deserve a 5 cent power switch?

The 32S was already cost-reduced to the point of a cereal-box-toy, but they discontinue it like they can't make any money. Yeah right, right on Carly.

NO STINKIN SOFT-MENU'S. You want to F, ENG, 4 ?
JUST DO IT. YOu don't have to hit 2nd, DISP
and then continue with a soft menu, like 32S.

I put this baby into Engineering Display mode,
does it say something bleccchy like

"14.142E0" ????


14.142 00

In nice clear crisp RED LED digits.


I got some nice "LABEL" buttons right up top,
label a program "A" or "B" and run it easily just
by pushing "A" or "B".

Think you could do that with a 32S ?????? HA HA HA HA HA HA no way charlie.

AND "RUN" bet that Carly is doing a speech right now
with her stinkin' powerpoint and excel spreadsheet,
to prove that slide switches are evil.





U gotta love that one kilohertz CPU speed. OOOO LAAA LAAAA. (OK I admit, if they speed that up with a
new CMOS chip, I'll accept that. But no other "improvements" from those who no longer bring good things to life.

THIS THING IS GEORGEOUS. Couldn't a done it w/o
the HP Museum. In fact the seller contacted me
because I tried posting a classified ad here. They bumped
into it off a google internet search. Not everybody
wants to setup to sell on eBay. Sometimes they want
to dump it quickly w/o creating an auction page.

Thanks dgh.

Every key push is like total ecstacy. Little keys
with little tiny hinges on them, where HP-32S has just
got a whole bunch stuck in there all blow-molded at
once. You get that flim-flammy feel on all those uninspired brown-plastic cereal box calculators because the keys aren't even free floating.

THIS THING IS AWESOME. A month ago, I said HP should
start making these HP-34C 's again...........

Now that I have had the good luck to acquire a nice



If I saw a kid trying to learn trigonometry and
calculus, I'd get him one of these. AWESOME.

And thanks to more modern high-power batteries,
the RED LED display is not something to fear.....
it's something to be ENJOYED .......


Hi my friend:
You are really happy, aren't you? Enjoy!
Thanks for sharing



Hey, Norm, from the Analog Lands! (are you the one?)

Do not give up s*x for your new "digital" tool/toy.

I wouldn't.

Be aware not going beyond the analog/digital limits... It may be a call without a return, you you understand me.

Anyway, I'm sincerely happy for you. I felt almost like this (my tunes were Brazilian ones) when I brought my HP41C back to life after 8 years inside a shoes box.

Best regards.

Luiz C. Vieira - Brazil

(As Raul Lion, I like reading about and sharing happy experiences with these folks in here; this forum must be THE place for this, too)


While I re-read the HP-34C owner's manual
to rediscover what made it such a cool machine,
I am busily COMPARING IT to the HP-32S.

If you just type in a scientific notation
number, like 25.251 E 08
I immediately noticed how much more nicely
it was formatted. The decimal number is
pressed to the far left, the exponent is
pressed to the far right. Crisp, clear
and you don't even need an "E" in the display.

The 32S crams it all together with no spaces
and an "E" to separate them.

OK, we can always find some sort of advantage
to the 32S. It has got 12 digits, the 34C
has only got 10. But so what, the 34C is
more fun. "happier than a hippy". This is what
the Microsoft and Carly types can't understand
its not how much resources you have, its what
you do with those resources. It's not whether
the hard drive is 10 gigabytes or 100 gigabytes,
its what you do with that resource.

One designer can build a beautiful machine with an economically constrained 10 digit display, the other builds something boring and dull with a 12 digit(or even more sophisticated) display.

VERY VERY HAPPY,and this HP-34C is stomping the 32S
all to pieces with one hand tied behind its back.

I got a little lucky, other than the classic pry-mark
damage at the bottom of the HP-34C, this unit is
like showroom new after I did a minor cleanup.

Wouldn't go so well if the unit were pounded to bits and had dried dog barf on it.
That's why there is supposed to be a thing called "factory" where they make new ones for us, and then we give the factory our money to go and get a new one. But Carly did away with that concept.

- Norm


Norm --

For future reference, here is the link for my "dental floss trick" for opening the case halves of Spice calc's, mentioned by Luiz Vieira and David Smith in this thread:

Using dental floss to open HP Spice-series calculators

I have digtal pictures of this, and would like to turn it into a tech article including Luiz' illustration.


Hello, Karl;

I'd be honored!

Use it as well. If you believe this one is also usefull, feel free using it too. I think with previous one you have a better view. Check it:

Best regards.

Luiz C. Vieira - Brazil


The best way to open a spice machine that I have found is to to remove the two screws at the top of the battery compartment. Next lift up on the back of the case so that it clears the battery contacts (you will probably have to press down on them to clear the cutout in the case). While holding the case back up away from the battery contacts you then want to squeeze the base back downward towards the label. I place my thumbs in the battery compartment and fingers on the front label. The latch that Luis drew so well, should pop loose.

I have seen a couple of machines that just would not pop loose though. You can try the dental floss trick or in a dire emergency just keep pulling the case back up. You will eventually hear the CRAAAACK of doom as the latch unlatches. I have never broken the latch, but it is a possibility.


These were all good ideas and very nice diagrams
about the SPICE series calculator case problem
such as HP-34C.

I like the dental-floss and might try it some time.

Did anybody NOTICE I mentioned the possibility of
trimming the plastic back a little with an X-Acto knife?

I think its a fairly good suggestion. Use
a super razor sharp X-acto.

You can't overdo such a trim, obviously. Just
like 5 thousandths of an inch.
Just a little goes a long way. You can trim it
right angle or even 45 it, as you prefer.

Its hard to describe which surfaces to trim, but there
are two points of 'hangup' that make the case so
horrible to dismantle. The edge of "the latch"
and the very lower edge of the bottom half.

Both edges to trim are on the bottom half plastic piece.

I did this bit of trimming so it would be easier to
take it apart in future.

There are other situations where you shouldn't feel
"stuck" with whatever gaffe the plastics manufacturer gives you. One such thing I have trimmed before, is a DVD box where its hanging on so tight it wants to bust the DVD
in half rather than let go of it. Use that trusty X-acto knife, but SPARINGLY.


What does MoHPC stand for?

Oh, does that dental floss have to
be MINT flavor or regular ?


You're kidding, right?

Just in case you aren't, MoHPC stands for Museum of HP Calculators!

Now. Who is buried in Grant's tomb?


nobody is buried in Grant's tomb

the whole thing is a hoax.



The correct answer to the age-old question, which is an example of one whose answer is not as obvious as it seems:

Ulysses S. Grant... *and* his wife.

Regarding the question Norm posed in "What is MoHPC": I used mint floss, but I have not compared waxed to unwaxed.

On lubing the slide switches: I am familiar with Norm's choice of Tri-Flow (having used it on bicycles). It used to be called Tri-Flon, but I guess Du Pont objected.
I had earlier asked the question in this Forum of what to use for these switches, and got a number of suggestions. One of those was Radio Shack Lube Gel, which I had already bought for the purpose.


Norm -- I'm worried for you. You're going to pop an artery!

(I wouldn't mind adding a 34C to my meagre holdings someday, myself.)

And if you like LED's so much, I've got a working TI-30 (very good condition) that I'll trade for that horrible LCD HP-32s (in just about whatever condition} . . . I might even throw in the TI-55, as well . . .

I suppose there's no use in my encouraging your enjoyment of your new acquisition -- it appears that you're doing quite well on your own!


Hello Paul;

The 32S is the thrasher calculator around the house.
I've got 4 of them actually. Some upstairs some
downstairs. The chinsy LCD and the long battery
life has its advantages. I can just grab one
and calculate when the need arises. In between
they get scratched up and dented and I don't even
care. The cats walk across them with yard mud
on their paws and thats OK too.

You wouldn't want to buy my 32S calculators because
they are all thrashed. I don't want to sell because
I still use them as thrashers. The 34C must necessarily
be used on the nicer occasions (because it is a
discontinued work of art and must be treated carefully).


Yes, really enjoying this thing. Last night I was
comparing INTEGRATE and SOLVE between an HP-34C
and the HP-32S. The 34C the procedure is VERY
SMOOTH to get started (slower to complete the operation of course). The 32S has got a bunch of
incomprehensible "definitions" that have to be
done in advance of starting. Wasteful extra
key-strokes, that furthermore add confusion.

You have to define which program is to be integrated.
With the HP-34C, you just do that at the moment
of beginning, you say (f) SOLVE "A". The "A" is
the program label. With the 32S you have to define
it by use of soft-menu's.

The HP-34C the variable is passed to the program
as the primary X-stack register, the obvious place.

But with the 32S, you have to define which register
the argument to the function is coming from.
Again, wasteful extra steps.

The 34C handles like a nice little Red Ferrari.
The 32S handles like a klunky brown & grey garbage truck.

That's what 15 years of "progress" gets you.

Enjoyed chatting, yes, having lots of fun 'rediscovering'.
Will continue to do comparisons of why the 34C ran so nicely.

NOTICED that the alphanumeric display really does NOT add much to the 32S. It adds clutter. The 34C is very crisp because they made best possible
usage of those 8's. I'd say its clearer and crisper, all in all, than the alphanumeric display.

I mean, all keys are labelled by their "row column" in the 34C and that's clear & crisp. With the 32S you get all
sorts of silly little extras. The INTEGRATE program gives you "(integral symbol) =" and then the symbols disappear as soon as you move on. Why add all this eye-candy.

Do they think they are in Hollywood? Eye-candy is their phrase for overcomplicating a scene and over-polishing all the chrome. Even in Hollywood eye-candy is bad.
It's cinematic junk food. I like 70's movies where they
shot more genuinely on a budget. The 32S has too much eye candy, but its all dull-grey-bland LCD eye candy.


Hi Norm:
I'm as lover of the 15c as you of the 34c... and they have the same solver. A solver for solving *one variable* equations. The 32s/42s solver is better: it can solve any variable in multiple variable equations.

Well, if you read this post:


then you will get another good new about your loved 34c.

I hope you enjoy your new solver as much as I do in my 15c



Paul --

I agree with you about the ease of use of Solve/Integrate with the 34C, 15C, and 41C Advantage Pac. Raul's post referenced one of mine, describing how to utilize Solve/Integrate on these calcs for a chosen variable in a multi-variable function without editing the function-definition user program.

I am writing one or two articles about these topics, but haven't fully decided their breadth and scope.

One interesting thing about Solve/Integrate on these calcs vs. the 32Sii: The user may perform Integrate within a program passed to Solve, or vice-versa -- computationally-intensive, but practical tasks. The 32Sii does not allow that. This was progress? A shame, because the 32Sii is about four times as fast as the 34C or 15C, and twice as fast as the 41C.

The 32's limited alphanumerics allows the user to see symbols for program steps instead of having to decipher keycode sequences, and to use more-descriptive letters for variables and program labels. This is good for small programs in "permanent residence", not so important otherwise.

I have a 32Sii and 12C for daily use at work; A PC with Matlab and Excel is on my desk for heavy computations or graphing. However, the one I'd take first to any exam is the 15C I've had since 1983. It's everything the 34C is and more, and ya don't have sit next to a wall socket. ;-)


Well, if you guys really like the LCD versions
better, its good, because that means less buyers
for HP-34C, and more HP-34c for me with less competition.

When I compare them directly, the 32S is an OBVIOUS
descendent of the 34C. All the clever ideas were done
in the 34C, the designers of 32S were just copycats
building it to the price of a cereal-box toy.

I'd rather have the genuine Mona Lisa than
a knock-off copy.

Just the reasoning behind
the enthusiasm that's all, don't mean to state
it too strongly because I understand you prefer
the greater computational horsepower of the newer unit.
But I am preferring the superior cosmetics of the 34C.

I notice some objections i had to 32S , are actually
fixed in 32Sii . Say you wish to convert 60 degrees
to radians. You type in 60 on a 34C.
Then you hit the "g" and "->R" . Quick, expedient,
no surprises, works great.

On the inferior 32S, you lose sight of the X-register,
thereby interrupting your train of thought, and it asks you by soft-menu whether you want ->D or ->R (into degrees or into radians). It is asking you this while you cannot even see what you started with (the 60 degrees), and it is
furthermore requiring an extra keystroke.

Nevertheless, this has been fixed on the 32Sii .
The 32Sii has that arranged more like the 34C .


I love the 34C, too - it's the only Spice model I have so I don't really know anything about the others. But as I have learned here, the Spice series appears to be HP's first attempt at calculator cost reduction that came with a loss of quality. The case and the keys are fine and the display is better that previous models, but the recharger connection with it's tin plated contacts is kind of flimsy. Tin plated contacts aren't meant to be used for a large number of mating cycles. The battery contacts break easily. The solderless IC assembly version looks like it would be unreliable but I don't know if it was, mine isn't that version.

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